Help - Genset Inop

[VinceB]

I picked up my 2001 Diplomat from the paint shop but have a problem.

Problem:  Onan 7500 diesel Gen start switch on dash is dead – does nothing. Same with switch on the genset.

Coincidentally, the radio switch on the dash (right next to gen sw on dash) is also dead.

What I found at home: No 12v in the house: the 200 amp fuse for the house batteries was blown.  I replaced the fuse and all 12v and 110v in the coach appear to work.

What I think happened: while at the paint shop, they left the key on and killed the chassis batteries (6 years old so not surprised). I delivered 2 new batteries so they could stop jumping it to get the coach started. While jumping or swapping out batteries, they caused a short somewhere and blew the 200 amp fuse. The new 200 amp fuse is holding.

I installed new house batteries when I got her home – took a pic so I know I’m spot on. However, I am not sure that they have the chassis batteries wired correctly. I was not allowed in the shop to do it myself.

If someone has a similar or same coach and can send a pic of what the chassis batteries and wiring look like, it would be a big help in troubleshooting. Below is a pic of how things are and they look correct to me. 2 different angles so you can get the whole picture.

I realize that if they have a negative to positive or vice versa, they possibly killed the mother board in the generator. I found a shop that can diagnose that, but can’t verify that the batteries are connected properly. There’s no sense in removing the genset, installing a new board, only to blow it again if the batteries are not connected properly.

All that said, if the batteries are connected properly and the board tests OK or put a new one in, what else could be the problem?

This is a totally foreign problem to be and so I have zero knowledge here.

[Steven P]

Vince,  here's a pic of my chassis setup.  I was waiting on my new house batteries at this time.  I noticed your 2 chassis batteries don't look the same.  I've always heard replace both w same brand, amperage, etc... could one of yours be bad?  However, I'm pretty certain my genny cranks from my house batteries and not the chassis ones.  I had to replace my dash generator start switch the other day bc it was failing.  Have you tried the batt boost switch?   When I had a bad house battery my genny wouldn't start, hold the boost switch for a minute w the chassis engine running and got it to fire up. 

[Tom Cherry]

On 11/14/2022 at 7:59 PM, VinceB said:

I picked up my 2001 Diplomat from the paint shop but have a problem.

Problem:  Onan 7500 diesel Gen start switch on dash is dead – does nothing. Same with switch on the genset.

Coincidentally, the radio switch on the dash (right next to gen sw on dash) is also dead.

What I found at home: No 12v in the house: the 200 amp fuse for the house batteries was blown.  I replaced the fuse and all 12v and 110v in the coach appear to work.

What I think happened: while at the paint shop, they left the key on and killed the chassis batteries (6 years old so not surprised). I delivered 2 new batteries so they could stop jumping it to get the coach started. While jumping or swapping out batteries, they caused a short somewhere and blew the 200 amp fuse. The new 200 amp fuse is holding.

I installed new house batteries when I got her home – took a pic so I know I’m spot on. However, I am not sure that they have the chassis batteries wired correctly. I was not allowed in the shop to do it myself.

If someone has a similar or same coach and can send a pic of what the chassis batteries and wiring look like, it would be a big help in troubleshooting. Below is a pic of how things are and they look correct to me. 2 different angles so you can get the whole picture.

I realize that if they have a negative to positive or vice versa, they possibly killed the mother board in the generator. I found a shop that can diagnose that, but can’t verify that the batteries are connected properly. There’s no sense in removing the genset, installing a new board, only to blow it again if the batteries are not connected properly.

All that said, if the batteries are connected properly and the board tests OK or put a new one in, what else could be the problem?

This is a totally foreign problem to be and so I have zero knowledge here.

Comments….

FIRST….STOP.  Go to the Chassis Batteries.  Verify that the RED Jumper is on BOTH positive terminals.  I can’t tell from the Picture.  Same for the Black Negative Jumper.  These batteries are in Parallel…

Also verify BOTH are 12 VDC.  Don’t mean to talk down, but shops have installed 12 VDC house batteries in SERIES and fried the electrical system. This is imperative before you proceed.

Next.  If you did not use a Bussmann ANL 200 amp “Ignition” fuse, order one on Amazon and replace it.  I can tell you that garden variety ANL fuses, especially the NON IGNITION (MARINE) ones will not last,  I carry spares for all the high current ANL fuses and they are OEM Bussmann.

Finally, you don’t say, but your House Bank could be shot, assuming that the House Cranks the Genny.  The easiest and simplest way to test.  AFTER you verify the Starting or Chassis batteries are configured properly, run a Battery Jumper cable from the RED positive on the Chassis/start to the RED POSITIVE on the House.

That is the same as holding IN the Battery Boost Switch.  BUT if the House Bank is dead, then you may not have enough voltage to engage the solenoid.  So this is just a Jumper that does the same thing,

If it cranks, then you know the House “cranks” the Genny, for future reference, and the House needs to be recharged or tested or replaced.  It takes about 3 - 4 hours to recharge a 4 battery House Bank with your 7.5 KW Genny.  Recharge them.  BEFORE you do this, assuming they are “dead or depleted”, check the electrolyte level in all cells.  Use Distilled Water and bring the level half way up or just touching or almost touching the bottom of the fill well.  Different batteries have different configurations.  If you use a wooden dowel and sit it on the plates, then mark the side of the dowel where the top of the plastic case is.  THEN use a flashlight and look inside the cell (safety glasses required), move the dowel UP until it is level with the bottom “well or plastic pieces inside the cell”.  Now remark the dowel using the same reference or top of the case.  ODDS ARE, the marks will be about 1 - 1 1/4 (maybe 1 1/2) inclines apart.  Take HALF that dimension.  Say 1 1/4” or half is 5/8”.  Then scribe a line using a knife 5/8” from the tip of the dowel.  This is NOW a dipstick and you know where to fill to.  You can be maybe 1/16 or 1/8” higher…..but NO MORE.  This works….

THEN recharge and remove the jumper and see how things are.  When you start the Genny, make sure that your inverter charger is ON and the Charge portion is ON,  sometimes when you lose power, it does not automatically start up or power on.

Edited November 18, 2022 by Tom Cherry
Added Battery Fill Level information

[VinceB]

6 hours ago, Steven P said:

Vince,  here's a pic of my chassis setup.  I was waiting on my new house batteries at this time.  I noticed your 2 chassis batteries don't look the same.  I've always heard replace both w same brand, amperage, etc... could one of yours be bad?  However, I'm pretty certain my genny cranks from my house batteries and not the chassis ones.  I had to replace my dash generator start switch the other day bc it was failing.  Have you tried the batt boost switch?   When I had a bad house battery my genny wouldn't start, hold the boost switch for a minute w the chassis engine running and got it to fire up. 

Both chassis batteries are brand new and identical - same brand and manufacturer. Just the cases are different because of supply line issues.

4 hours ago, Tom Cherry said:

Comments….

FIRST….STOP.  Go to the Chassis Batteries.  Verify that the RED Jumper is on BOTH positive terminals.  I can’t tell from the Picture.  Same for the Black Negative Jumper.  These batteries are in Parallel…

Also verify BOTH are 12 VDC.  Don’t mean to talk down, but shops have installed 12 VDC house batteries in SERIES and fried the electrical system. This is imperative before you proceed.

Next.  If you did not use a Bussmann ANL 200 amp “Ignition” fuse, order one on Amazon and replace it.  I can tell you that garden variety ANL fuses, especially the NON IGNITION (MARINE) ones will not last,  I carry spares for all the high current ANL fuses and they are OEM Bussmann.

Finally, you don’t say, but your House Bank could be shot, assuming that the House Cranks the Genny.  The easiest and simplest way to test.  AFTER you verify the Starting or Chassis batteries are configured properly, run a Battery Jumper cable from the RED positive on the Chassis/start to the RED POSITIVE on the House.

That is the same as holding IN the Battery Boost Switch.  BUT if the House Bank is dead, then you may not have enough voltage to engage the solenoid.  So this is just a Jumper that does the same thing,

If it cranks, then you know the House “cranks” the Genny, for future reference, and the House needs to be recharged or tested or replaced.  It takes about 3 - 4 hours to recharge a 4 battery House Bank with your 7.5 KW Genny.  Recharge them.  BEFORE you do this, assuming they are “dead or depleted”, check the electrolyte level in all cells.  Use Distilled Water and bring the level half way up or just touching or almost touching the bottom of the fill well.  Different batteries have different configurations.  If you use a wooden dowel and sit it on the plates, then mark the side of the dowel where the top of the plastic case is.  THEN use a flashlight and look inside the cell (safety glasses required), move the dowel UP until it is level with the bottom “well or plastic pieces inside the cell”.  Now remark the dowel using the same reference or top of the case.  ODDS ARE, the marks will be about 1 - 1 1/4 (maybe 1 1/2) inclines apart.  Take HALF that dimension.  Say 1 1/4” or half is 5/8”.  Then scribe a line using a knife 5/8” from the tip of the dowel.  This is NOW a dipstick and you know where to fill to.  You can be maybe 1/16 or 1/8” higher…..but NO MORE.  This works….

THEN recharge and remove the jumper and see how things are.  When you start the Genny, make sure that your inverter charger is ON and the Charge portion is ON,  sometimes when you lose power, it does not automatically start up or power on.

House batteries are all new and I brought them all up before installing them. They are wired correctly as are the chassis batteries.

I replaced the 200a fuse with what was in it. Don't recall but I'll read the spare and post later.

[VinceB]

Here is the fuse I replaced.  I also found a 15a inside the cover on the genset that was blown.  All working fine now.

Edited November 18, 2022 by VinceB