Generator Stalling Out

[Gene Y]

Generator stalling under load.

Generator will start and run, when the AC tries to start the generator dies! Have checked the coolant level and it is fine.

Looking for ideas,

Thanks 

[Guest Ray Davis]

Fuel filter?    Does it die with each AC unit individually?

[Tom Cherry]

1 hour ago, Gene Y said:

Generator stalling under load.

Generator will start and run, when the AC tries to start the generator dies! Have checked the coolant level and it is fine.

Looking for ideas,

Thanks 

Basic assumption.  I once did a “swap” and the generator tried to start and run with a 50% load.  UGLY.  I let the generator “rest” for maybe half and hour.  Then restart with NO AC load….ran for maybe 30 minutes.  All the load was just topping off the batteries.  If your batteries were down and 3 AC ON, that is close to 80% of the rating….if you have the 10Kw unit.

If it has stopped there may be an error code.  But if you kill all the loads….you will have to go into the Magnum set up and reduce the charge rate to maybe 10%….

Let it idle….then bring on loads progressively.  Your 10 KW may have crappy brushes….so it is not putting out 100%.  The “fix” for that….  Let it get warmed up.  Then one AC at a time.  Leave the magnum at reduced load or just turn off the Charger section.  There is a button that says charger. If you see the CHG light on….push the button.  That kills the charger section.  However, with the Genny running. You have AC POWER.  LET it run for maybe 30 minutes…bring on another AC…REPEAT.  Waiting 30minutes….once all 3AC ON….wait 30 minutes….turn on charger.  You can cook and use the microwave.

you need to run the Generator for several hours at 50 - 75% of load.  Do that every 6 - 9 months.  That will clean and burnish the brushes.

NOTE….This is for a 220 VAC 10 or 12 KW GENERATOR.  The 7.5 or 8 KW DOES NOT have brushes….

If you still have issues….new air filter.  Easy to do.  Then a new fuel filter….need 2 pairs of PINCH pliers or two pairs of Vice Grips and rags to pinch off fuel dripping when you replace.

Past that….read the manual and get codes.  The 10/12 Kw are prone to the main control board getting wet or failing.  Many rebuilt ones. Lots of reputable and knowledgeable techs always have a rebuilt and/or maybe a new one in their truck.  

Thats the drill

[96 EVO]

Recall when my front AC start capacitor had a meltdown, it was pulling huge amps everytime the compressor tried to start!

Is your AC's running fine on shore power?

[windsorbill06]

i would suspect your air conditioner.  Try other devices and see if you can isolate it down to 1 thing shutting down  the generator.

[Gene Y]

3 hours ago, Ray Davis said:

Fuel filter?    Does it die with each AC unit individually?

Have only tried the front unit.

3 hours ago, 96 EVO said:

Recall when my front AC start capacitor had a meltdown, it was pulling huge amps everytime the compressor tried to start!

Is your AC's running fine on shore power?

Yes it runs fine on shore power!

3 hours ago, Tom Cherry said:

Basic assumption.  I once did a “swap” and the generator tried to start and run with a 50% load.  UGLY.  I let the generator “rest” for maybe half and hour.  Then restart with NO AC load….ran for maybe 30 minutes.  All the load was just topping off the batteries.  If your batteries were down and 3 AC ON, that is close to 80% of the rating….if you have the 10Kw unit.

If it has stopped there may be an error code.  But if you kill all the loads….you will have to go into the Magnum set up and reduce the charge rate to maybe 10%….

Let it idle….then bring on loads progressively.  Your 10 KW may have crappy brushes….so it is not putting out 100%.  The “fix” for that….  Let it get warmed up.  Then one AC at a time.  Leave the magnum at reduced load or just turn off the Charger section.  There is a button that says charger. If you see the CHG light on….push the button.  That kills the charger section.  However, with the Genny running. You have AC POWER.  LET it run for maybe 30 minutes…bring on another AC…REPEAT.  Waiting 30minutes….once all 3AC ON….wait 30 minutes….turn on charger.  You can cook and use the microwave.

you need to run the Generator for several hours at 50 - 75% of load.  Do that every 6 - 9 months.  That will clean and burnish the brushes.

NOTE….This is for a 220 VAC 10 or 12 KW GENERATOR.  The 7.5 or 8 KW DOES NOT have brushes….

If you still have issues….new air filter.  Easy to do.  Then a new fuel filter….need 2 pairs of PINCH pliers or two pairs of Vice Grips and rags to pinch off fuel dripping when you replace.

Past that….read the manual and get codes.  The 10/12 Kw are prone to the main control board getting wet or failing.  Many rebuilt ones. Lots of reputable and knowledgeable techs always have a rebuilt and/or maybe a new one in their truck.  

Thats the drill

Just to clarify, this occured with engine running and on the road. So I'm assuming that the alternator was charging the batteries. The batteries were actually fully charged when we left last campground. Will try some of those remedies. Has been awhile since I used the generator for power.

Thanks Tom

[Tom Cherry]

42 minutes ago, Gene Y said:

Have only tried the front unit.

Yes it runs fine on shore power!

Just to clarify, this occured with engine running and on the road. So I'm assuming that the alternator was charging the batteries. The batteries were actually fully charged when we left last campground. Will try some of those remedies. Has been awhile since I used the generator for power.

Thanks Tom

No sense in tearing apart something that ain’t broke.  Since you have eliminated a faulty or presumed faulty AC…I’d stay with the simple basics.  At CG, unplug shore.  Turn off inverter.  Start genny.  Let it run for several minutes….at least 5.  Start loading it up one load at a time.  You have got 5 devices to do a load test…3 AC, Microwave and Charger.  Start one at a time….let it run at least 15 minutes….then add one.  AC’s are easiest.  If it dies or sputters or won’t run….MAYBE fuel? Air Filter? Or Board.  Read the Generator manual and learn how to get blinking codes….then proceed.

If it runs and you can keep building, then don’t push it.  The heavier the load and the longer you can run OK at that, then good sign.  No guarantees….but dirty brushes are a common complaint.  I don’t know if there is a code for that, but letting it run and building up a load is positive.  You might want to check the OIL LEVEL.  There is a cutoff for that.  When you get to CG, check the oil level.   Then proceed…

Good Luck…

[96 EVO]

When was the last time it got a fresh fuel filter?

They will last a long time due to the pickup about 1/3 way up the tank............... but not forever!

[Dr4Film]

One idea would be to check for an error code first.

[Gene Y]

On 7/5/2023 at 9:21 PM, 96 EVO said:

When was the last time it got a fresh fuel filter?

They will last a long time due to the pickup about 1/3 way up the tank............... but not forever!

Replaced fuel filter 6 months ago but I do have another one if needed. Thanks 

[96 EVO]

No, your not going to need a new filter in 6mo.

[Tom Cherry]

The manual gives an HOUR interval or schedule for all filters.  I routinely put in a new Air Filter every year.  My “OCD”.  

However, based on a LOT of feedback from folks and common sense, IF you get “bad” or partially contaminated fuel and have to add the Startron Stare Brite (memory) to clean it up as well as changing both fuel filters, you need to also pit in a new Genny filter.  That filter is smaller and will clog up quicker than the Engine.  Never run the generator if you know you have bad fuel and are more concerned about getting the engine running.  That has happened many times and one individual had major issues….even after cleaning the fuel, twice.  

Bottom line, follow the hourly schedule for the genny fuel filter….unless you rarely use it….then common sense says to go to a shorter (maybe 2/3 of the hours) to prevent issues….especially if you don’t treat each fillup with J F Biobor to prevent algae.  Algae plays havoc with the smaller genny filters.

[Gene Y]

On 7/5/2023 at 4:05 PM, Tom Cherry said:

No sense in tearing apart something that ain’t broke.  Since you have eliminated a faulty or presumed faulty AC…I’d stay with the simple basics.  At CG, unplug shore.  Turn off inverter.  Start genny.  Let it run for several minutes….at least 5.  Start loading it up one load at a time.  You have got 5 devices to do a load test…3 AC, Microwave and Charger.  Start one at a time….let it run at least 15 minutes….then add one.  AC’s are easiest.  If it dies or sputters or won’t run….MAYBE fuel? Air Filter? Or Board.  Read the Generator manual and learn how to get blinking codes….then proceed.

If it runs and you can keep building, then don’t push it.  The heavier the load and the longer you can run OK at that, then good sign.  No guarantees….but dirty brushes are a common complaint.  I don’t know if there is a code for that, but letting it run and building up a load is positive.  You might want to check the OIL LEVEL.  There is a cutoff for that.  When you get to CG, check the oil level.   Then proceed…

Good Luck…

Sorry for the delayed response, currently in a somewhat remote area of Canada along the St. Lawrence River.

This morning I ran the generator for over an hour as suggested. Had no problems with it running, all loads turned off. I then started the front AC and it ran with no issues. Still no issues after turning on the inverter then the electric water heating element. Thought I was good to go. Ready to leave campground I started up the engine, generator shut down and would not stay running after multiple attempts of starting.

So what does this point to? Weak chassis batteries? Alternator not putting out enough power? Big Boy relay faulty? Or none of the above?

Thanks again for your help!

[Rocketman3]

Does your generator start on the Chassis battery or the house battery. Monaco did it both ways in different years. 
 

My rig the generator is on the Chassis battery. If the generator is running and I try to start the diesel engine- it kills the generator and I get generator errors - either the ignition switch kills the power as the start circuit is engaged or the voltage drops so low the generator quits. I read somewhere that is NOT good for the generator (can fry an electronics board - don’t know if it’s true or not) so I try not to do it. 

I usually don’t drive with the generator on. But I have (just have to remember to shut it down before starting. 

my generator is the 7.5

Good Luck

Edited July 8, 2023 by Rocketman3

[Tom Cherry]

13 hours ago, Gene Y said:

Sorry for the delayed response, currently in a somewhat remote area of Canada along the St. Lawrence River.

This morning I ran the generator for over an hour as suggested. Had no problems with it running, all loads turned off. I then started the front AC and it ran with no issues. Still no issues after turning on the inverter then the electric water heating element. Thought I was good to go. Ready to leave campground I started up the engine, generator shut down and would not stay running after multiple attempts of starting.

So what does this point to? Weak chassis batteries? Alternator not putting out enough power? Big Boy relay faulty? Or none of the above?

Thanks again for your help!

Comments about LOW battery and where it cranks are interesting.  Monaco did it totally different and then swapped around.  Typically, the Generator was supposed to crank off the House Bank.  That is so you can use the battery boost as the Generator will or can be charging the House Bank and get you going. 

EDITED....after some thought....  OK...when you said ALL IS WELL.  Did you TOTALLY load up the Generator with three AC's (if you have them) and run it for some time to clean the brushes.  Your three items was only about 50% (Don't know what the Inverter was pulling) of the load.  You need to run the generator as close to full load....adding in the two other AC's and then run for a few hours.  That will clean the brushes and keep you in good shape.  MAY NOT BE THE PROBLEM....but it needs to be done....

I had TWO issues with my system.  One was a GROUND stud issue.  Genny would NOT start. I used Jumper cables and started it directly with cables to the back terminals.  GREAT.  Ran fine.  Would NOT restart without them.  I found out there was corrosion on the battery ground studs behind the battery box.  Fixed...NO ISSUES.  The other was when I was on SHORE.  I started the Genny....and then tripped the pedestal breaker and unhooked.  OPPS.  Genny was not warmed up.  The AC load switched and both came on.  Waited a while after driving.  Restarted the Genny and then brought on one AC....then the other.  GREAT.  SO....that is a lesson in WHAT NOT TO DO....   Read the rest.... END OF EDIT.

First....  Turn off the Chassis Bank.  Will the Generator crank or start to crank?  If so, then the House is starting the Generator. 

Second.  Turn back ON the Chassis and turn OFF the House.  Then run your cranking test.  I looked at the High Current prints for a 2004, but the way Monaco does the prints, I can't trace them.  our set is a bit "light" or faded.

OK....Now that you know WHICH battery cranks....it might be time to read the manual again.  Is there a warning about keeping the Generator ON while Cranking.

Next TEST, as Rocketman says.  Turn off the Generator.  Crank the Engine.  Get rolling and wait a few minutes.  Then crank the generator and wait and then load it up as you drive.  If that works OK....then you know that the Alternator seems to be OK.  I THOUGHT you had an Alladin.  There are screens for voltage and current.  You need to read up on that and see what is going on.

Past that, until you do some experimenting....then it is strictly subjective.  From what you said, everything, when at a CG and using the Generator works.  IS THAT CORRECT?  If so, then that would eliminate Fuel issues. 

You also need to know that the Generator does not have an Alternator.  The Power to run the Generator (keep it running) comes from the Starting Battery lugs.  MANY TIMES, and this impacted me, a POOR GROUND in the system will cause issues.  SO, chasing that down is fairly easy.  You follow the Negative Cables from the battery box(s) to the ground studs.  You either remove all the cables (one stud at a time) and clean or you loosen the nut slightly, just so the cables will wiggle side to side, and then do that.  That abrades or cleans the terminals.  There are two Ground studs on the back...One for Chassis and one for House. There is at least ONE or maybe two up front.  You need to be under the MH and see where the Negative cable to the generator goes.  Clean that one.  Whilst there...loosen BOTH the positive and negative on the rear or wherever the DC cables are attached.  Clean the terminals and the studs.  Put back on.  DO NOT OVERTIGHEN.  These are brass studs and if you "lay down on them..." there is a chance (I have been TOLD...) that one will break.  So the old trick of just "TIGHTENER UP" results in replacing the stud...

OK....Lot of possibilities.  IF you drive and load up the Generator like you did and all is well, then there is a voltage problem somewhere....as Rocketman said.  I can tell you that the board on the 10/12 KW is not the most robust.  So, DO NOT CRANK THE GENNY with the Engine running.  

One simple test....if you have jumper cables and are in the CG.  Put a Jumper between the POSITIVES of the Batteries.  Start the Generator.  Then, as I understood you to say, when you started the Engine with the Generator running, it would NOT stay running.  If that is STILL the issue....then STOP.  NOW.  Wait a few minutes.  Maybe the NEXT DAY.  Add a Jumper to the NEGATIVES.  Leave the Positive ON ALSO.  Now start the Genny just like you did when the problem occurred.  Now start the Engine.  IF you have NO issues....then you have a GROUND issue and you need to clean all the GROUNDS....on the Chassis (there are many....4 on mine....more on yours?.  You also need to clean the battery terminals.  If that does not fix it....then someone with a VOM and knowledge needs to start troubleshooting.  This is a bit involved....so not going there now.

Try the above....let us know. 

[jacwjames]

FWIW

I had a problem with my generator in 2021 on a trip and ended up having to high tail it home. 

Was running generator with one AC running when all of a sudden it quit but it was evening and cool enough to just go to bed.  Next day hit the road and didn't try the generator until later that day, no luck, it would start but as soon as transfer switch closed the generator would die.     I did try to do some trouble shooting, I turned off all the breakers and started generator, it stayed running and one by one I turned on breakers doing the 50 amp first, stayed running, then one by one starting with breakers to the inverter subpanels and eventually the generator quit on one of the two breakers.   I thought it was an internal problem with the inverter/ Was able to keep batteries charged by driving, no dry camping so after one more stop I went home.

Once home I actually took the inverter out to inspect, could find nothing wrong and took some ohm readings on the two circuits, one was different and I thought that might be the problem, called Trace support and the tech said YES this was the problem said it was probably the pass through relay which was obsolete and gave me the info on what I need to replace the inverter  which was $$$$$.

So more searching and found a place near Nashville that does inverter repair, explained my problem and said he thought the inverter was OK and that it was a wiring problem in the coach and gave me some tips on how to trouble shoot.  I put the inverter back in and started troubleshooting doing about what I was doing before except I turn off all the subpanel breakers and then started turning the all the breakers on one by one.  Turned out it was one of the inverter circuits, the one that supplied power to the bedroom, 1/2 bath, and basement.  What was weird was that everything worked fine on shore power!!!.

So I concentrated on that circuit and ultimately found that I did I had a slight short between the hot and neutral, measures some ohms between the wires and traced it to the portion of wire in the ceiling with no way to repair so I had to abandon that section of wire  BUT I was able to get creative and change the way the circuit was daisy chained and get all outlet working. 

I suspect the wiring problem was due to a mouse infestation I had while I had the rig parked while building our house.   Finally solved that problem when I built a garage to park the rig in.

I guess the generator must have sensed the slight short in the wiring and shut down.  The problem was on a GFCI which didn't trip but didn't trip due to the slight short.

 

Edited July 8, 2023 by jacwjames

[Tom Cherry]

14 minutes ago, jacwjames said:

FWIW

I had a problem with my generator in 2021 on a trip and ended up having to high tail it home. 

Was running generator with one AC running when all of a sudden it quit but it was evening and cool enough to just go to bed.  Next day hit the road and didn't try the generator until later that day, no luck, it would start but as soon as transfer switch closed the generator would die.     I did try to do some trouble shooting, I turned off all the breakers and started generator, it stayed running and one by one I turned on breakers doing the 50 amp first, stayed running, then one by one starting with breakers to the inverter subpanels and eventually the generator quit on one of the two breakers.   I thought it was an internal problem with the inverter/ Was able to keep batteries charged by driving, no dry camping so after one more stop I went home.

Once home I actually took the inverter out to inspect, could find nothing wrong and took some ohm readings on the two circuits, one was different and I thought that might be the problem, called Trace support and the tech said YES this was the problem said it was probably the pass through relay which was obsolete and gave me the info on what I need to replace the inverter  which was $$$$$.

So more searching and found a place near Nashville that does inverter repair, explained my problem and said he thought the inverter was OK and that it was a wiring problem in the coach and gave me some tips on how to trouble shoot.  I put the inverter back in and started troubleshooting doing about what I was doing before except I turn off all the subpanel breakers and then started turning the all the breakers on one by one.  Turned out it was one of the inverter circuits, the one that supplied power to the bedroom, 1/2 bath, and basement.  What was weird was that everything worked fine on shore power!!!.

So I concentrated on that circuit and ultimately found that I did I had a slight short between the hot and neutral, measures some ohms between the wires and traced it to the portion of wire in the ceiling with no way to repair so I had to abandon that section of wire  BUT I was able to get creative and change the way the circuit was daisy chained and get all outlet working. 

I suspect the wiring problem was due to a mouse infestation I had while I had the rig parked while building our house.   Finally solved that problem when I built a garage to park the rig in.

I guess the generator must have sensed the slight short in the wiring and shut down.  The problem was on a GFCI which didn't trip but didn't trip due to the slight short.

 

Interesting.  Assume you have the 7.5/8 KW. OP has the 220 (brushes not rectified) Onan. I assume, please confirm, that you go no error codes on the Genny.  Eventually we need for the OP to check for error codes if it shuts down again.  His issue may be what happened to Rocetman.  We need more info and results from testing….

However, if i read correct, his Genny, tested OK for a long while….not fully loaded which would have cleaned the brushes….so fuel and air seem OK.

THANKS for the input.  These rascals are tricky and the circuitry is like none other.

[Dr4Film]

I have owned a 7.5K generator in my 2002 Windsor and now own a 10K generator in my 2006 Dynasty. I had to get used to the differences in their operation.

The 7.5K started from the House Battery Bank and because it is an Inverter Generator it would ramp up speed as I put more load onto the generator.

The 10K starts from the Chassis Battery Bank and it runs at a constant speed/rpm so the sound doesn't change as more loads are put onto it. The only characteristic of this 10K which I don't like is that I don't consider it to be an Onan QD aka Quiet Diesel Generator. It is far noisier than the 7.5K I had in the Windsor even when it was running at full capacity.

Like @Rocketman3 if I attempt to start the engine while the 10K generator is running it will kill the generator. I believe it is due to low voltage as the starter is drawing way too many amps from the Chassis Battery Bank.

[Tom Cherry]

1 minute ago, Dr4Film said:

I have owned a 7.5K generator in my 2002 Windsor and now own a 10K generator in my 2006 Dynasty. I had to get used to the differences in their operation.

The 7.5K started from the House Battery Bank and because it is an Inverter Generator it would ramp up speed as I put more load onto the generator.

The 10K starts from the Chassis Battery Bank and it runs at a constant speed/rpm so the sound doesn't change as more loads are put onto it. The only characteristic of this 10K which I don't like is that I don't consider it to be an Onan QD aka Quiet Diesel Generator. It is far noisier than the 7.5K I had in the Windsor even when it was running at full capacity.

Like @Rocketman3 if I attempt to start the engine while the 10K generator is running it will kill the generator. I believe it is due to low voltage as the starter is drawing way too many amps from the Chassis Battery Bank.

Thanks for adding more “Amens” to “DO NOT START ENGINE WITH GENERATOR RUNNING”….in the 2000 - 2006 Dynasty and/or maybe higher end models.  This phenomenon is fascinating…..  maybe it ain’t broke, but as old Doc Campbell in Hee Haw prescribed….”If it hurts when you do a crazy move with your left hand….don’t do that anymore….$5 please but take 2 aspirin in the morning …. “..LOL

[Gene Y]

3 hours ago, Tom Cherry said:

Comments about LOW battery and where it cranks are interesting.  Monaco did it totally different and then swapped around.  Typically, the Generator was supposed to crank off the House Bank.  That is so you can use the battery boost as the Generator will or can be charging the House Bank and get you going. 

EDITED....after some thought....  OK...when you said ALL IS WELL.  Did you TOTALLY load up the Generator with three AC's (if you have them) and run it for some time to clean the brushes.  Your three items was only about 50% (Don't know what the Inverter was pulling) of the load.  You need to run the generator as close to full load....adding in the two other AC's and then run for a few hours.  That will clean the brushes and keep you in good shape.  MAY NOT BE THE PROBLEM....but it needs to be done....

I had TWO issues with my system.  One was a GROUND stud issue.  Genny would NOT start. I used Jumper cables and started it directly with cables to the back terminals.  GREAT.  Ran fine.  Would NOT restart without them.  I found out there was corrosion on the battery ground studs behind the battery box.  Fixed...NO ISSUES.  The other was when I was on SHORE.  I started the Genny....and then tripped the pedestal breaker and unhooked.  OPPS.  Genny was not warmed up.  The AC load switched and both came on.  Waited a while after driving.  Restarted the Genny and then brought on one AC....then the other.  GREAT.  SO....that is a lesson in WHAT NOT TO DO....   Read the rest.... END OF EDIT.

First....  Turn off the Chassis Bank.  Will the Generator crank or start to crank?  If so, then the House is starting the Generator. 

Second.  Turn back ON the Chassis and turn OFF the House.  Then run your cranking test.  I looked at the High Current prints for a 2004, but the way Monaco does the prints, I can't trace them.  our set is a bit "light" or faded.

OK....Now that you know WHICH battery cranks....it might be time to read the manual again.  Is there a warning about keeping the Generator ON while Cranking.

Next TEST, as Rocketman says.  Turn off the Generator.  Crank the Engine.  Get rolling and wait a few minutes.  Then crank the generator and wait and then load it up as you drive.  If that works OK....then you know that the Alternator seems to be OK.  I THOUGHT you had an Alladin.  There are screens for voltage and current.  You need to read up on that and see what is going on.

Past that, until you do some experimenting....then it is strictly subjective.  From what you said, everything, when at a CG and using the Generator works.  IS THAT CORRECT?  If so, then that would eliminate Fuel issues. 

You also need to know that the Generator does not have an Alternator.  The Power to run the Generator (keep it running) comes from the Starting Battery lugs.  MANY TIMES, and this impacted me, a POOR GROUND in the system will cause issues.  SO, chasing that down is fairly easy.  You follow the Negative Cables from the battery box(s) to the ground studs.  You either remove all the cables (one stud at a time) and clean or you loosen the nut slightly, just so the cables will wiggle side to side, and then do that.  That abrades or cleans the terminals.  There are two Ground studs on the back...One for Chassis and one for House. There is at least ONE or maybe two up front.  You need to be under the MH and see where the Negative cable to the generator goes.  Clean that one.  Whilst there...loosen BOTH the positive and negative on the rear or wherever the DC cables are attached.  Clean the terminals and the studs.  Put back on.  DO NOT OVERTIGHEN.  These are brass studs and if you "lay down on them..." there is a chance (I have been TOLD...) that one will break.  So the old trick of just "TIGHTENER UP" results in replacing the stud...

OK....Lot of possibilities.  IF you drive and load up the Generator like you did and all is well, then there is a voltage problem somewhere....as Rocketman said.  I can tell you that the board on the 10/12 KW is not the most robust.  So, DO NOT CRANK THE GENNY with the Engine running.  

One simple test....if you have jumper cables and are in the CG.  Put a Jumper between the POSITIVES of the Batteries.  Start the Generator.  Then, as I understood you to say, when you started the Engine with the Generator running, it would NOT stay running.  If that is STILL the issue....then STOP.  NOW.  Wait a few minutes.  Maybe the NEXT DAY.  Add a Jumper to the NEGATIVES.  Leave the Positive ON ALSO.  Now start the Genny just like you did when the problem occurred.  Now start the Engine.  IF you have NO issues....then you have a GROUND issue and you need to clean all the GROUNDS....on the Chassis (there are many....4 on mine....more on yours?.  You also need to clean the battery terminals.  If that does not fix it....then someone with a VOM and knowledge needs to start troubleshooting.  This is a bit involved....so not going there now.

Try the above....let us know. 

Sounds like a plan Tom, my mistake on not totally loading the generator after warming up the generator. Will try that first. The rig did originally have the Aladdin system but at some point PO changed it to a different system and it is in inoperable. I like the suggestion to shut off chassis batteries to determine which starts the generator. Pretty sure it starts off chassis batteries but need to know for sure.

Thanks again!

[Tom Cherry]

1 hour ago, Gene Y said:

Sounds like a plan Tom, my mistake on not totally loading the generator after warming up the generator. Will try that first. The rig did originally have the Aladdin system but at some point PO changed it to a different system and it is in inoperable. I like the suggestion to shut off chassis batteries to determine which starts the generator. Pretty sure it starts off chassis batteries but need to know for sure.

Thanks again!

One step at a time.  Sounds like this is a common occurrence….but preventable….so, learn how to avoid the issue. Get your brushes cleaned and keep doing that.  Then enjoy.  If you have “weak”chassis batteries….the test, and it needs to be HOT…maybe in the 90’s.  Stop in the heat of the day.  Should have been driving for a few hours.  Turn off the engine.  Stop at a rest stop or whatever.  Wait about 5 - 10 minutes.  The engine will, naturally, heat up.  Then listen carefully and leave the Front Dash AC on….or make sure it is ON.  If there is a pause or hesitation…..and you panic and get that OMG…it ain’t gonna start….but then turns over and starts fine….maybe Chassis in the next year or so.  The hot engine has expanded and takes MORE current.  

[jacwjames]

5 hours ago, Tom Cherry said:

Interesting.  Assume you have the 7.5/8 KW. OP has the 220 (brushes not rectified) Onan. I assume, please confirm, that you go no error codes on the Genny.  Eventually we need for the OP to check for error codes if it shuts down again.  His issue may be what happened to Rocetman.  We need more info and results from testing….

However, if i read correct, his Genny, tested OK for a long while….not fully loaded which would have cleaned the brushes….so fuel and air seem OK.

THANKS for the input.  These rascals are tricky and the circuitry is like none other.

I had no codes on the generator.  It would just die if one breaker was flipped on.

[Tom Cherry]

Gentlemen, assumed of course…. It hit me last night, upon retiring, what the issue is.  I did some checking and ran my ideas by an esteemed expert.  Bottom line….NOTHING AIIN’T BROKE.  It is a Phenomenon that exists and what is happening is logical…but depending on certain things, it WILL or MAY show up….but only in a rare situation is “Something is broke”.

When you start your engine and pay close attention to a Digital “Dash Gauge” while it warms up or usually in my case, while in storage, the air compressor is running full time as I have a LOW AIR.  perfectly normal and happens….when in extended storage…..this is what is also happening…

There is a array or “bank” of intake air heaters.  They will be on briefly or for a few minutes depending on the temperature of the engine and the ambient.  Those toaster elements are sucking up every milliamp of DC current they can find.  I thought there was a “ECM” delay built in so that the alternator would not charge until the engine had run a few minutes.  In effect, that is what’s happening….but it is current draw, which can or does correlate to voltage drop.

Most that crank their 10/12 KW Onan from the Chassis experience it but it may NOT enough to cause an issue.  When you crank you draw down or drop the voltage.  The alternator is feeding the intake heaters like gangbusters.  When they have been satisfied and shut off, then the current goes to batteries and the Chassis will start to recharge.  Natural and logical.

NOW…why does it impact the generator?  The answer is a bit nebulous, but there are certain parameters that could be involved.  

FiIRST…..the condition of the house batteries.  The older, the more likely as they deteriorate over time.  Doesn’t mean they will not crank, but when they only have say, 60% or more….then their voltage drop will be lower.  Conversely, the colder the engine, the more amps were used….as well as the longer the heaters will be on….therefore the LONGER and LOWER the engine voltage will be.

SECOND…, the sensitiviy of the Generator’s PCB.  Each board has its own built in parameters or alarm (voltage) factory tolerance.  But that can vary.  Magnum says, the voltage you see on the remotes is only +/- 10%.  That is a heck of a tolerance.  Your DVM is probably less than 1%.  But the Magnum meter is then the “MASTER” and it will trigger low voltage or high or your AGS….often times with a “Must be below alarm set point” for X seconds or minutes.  The Generator has, logically, the same tolerances.  So, pop out a board from one and put it in another genny….may or may NOT have the same characteristics.

Bottom line, MOST LIKELY the shutting down is from a low chassis battery.  The engine is running and is fine,  but the entire system voltage drops down and does not stabilize until the heaters turn off.  I have watched mine and sometimes the air will build up on a medium cold (upper 30/low 40”s) and the low pressure alarms are satisfied and I back out and notice the voltage is barely 12 VDC….then all of a sudden….13.9   It literally JUMPS….as in the heaters shut off and now almost 160 A is going to the batteries and the system voltage ramps or jumps up. If the generator PCB board sees a “LOW VOLTAGE” reading….it might go away or fluctuate.  Eventually if low enough, the alarm shuts down the generator.  Then wait a few minutes….restart….without then restarting the engine or the enine running….voltage is high enough…  if the engine is not running, then the batteries didn’t pull near as much….less than 10% of what the engine did.  No alarm.  No shutdown.

NOW…i will never see what you guys are seeing as my genny cranks off the house.  That is what is happening and the conditions will dictate whether it shuts down.  There MAY be, low probability, am issue with the PCB or main board…as these 10/12 are prone to more issues than the 7.5/8KW….

BUT, most likely….nothing is wrong.  Just shut down your Generator before starting the engine….let the voltage stavilize and get into the 13.8/14.0 normal range….then RESTART the genny.  If this bothers you, then put in a separate battery, as some have, for the genny….typically being recharged by the inverter and then becomes part of the house bank.

That’s it.  If you want to monitor the condition of your cranking batteries, the shut down when really hot (90 or higher) and wait 5 - 10 minutes and with the Front AC ON, restart.  Hesitation means the batteries are starting not to recharge to 100%….time to plan ahead or have a Jumper cable and jumper the House and Chassis…

In another thread, i stated the exact way, simple, to test or measure the SOC with only a DVOM and no fancy load meter….

[Gene Y]

Awesome Tom, wishing I had half of the knowledge that you have. I will be following your suggestion at my next opportunity. Where we are at right now there is no need to run the house AC while driving.

Thanks again!

[Guest Ray Davis]

36 minutes ago, Gene Y said:

Where we are at right now there is no need to run the house AC while driving.

Gene, where is that?  I wanna go there!!