Alt Charge flashing Gremlin - Suggestions and understanding appreciated

[BradHend]

On my latest trip my “Alt. Charge” light keeps intermittently lighting up, or slightly pulsing on/off.

I’m not overheating and the serpentine belt is fine.  I did change the (4) 6V house batteries 3 weeks ago,  but that shouldn’t have anything to do with it I don’t believe. 
I still maintain about 13.7 volts with the engine running and about 12.8 with it off and no issues starting. 
Any thoughts?

[Dr4Film]

What voltage does your VOLTS gauge display with the engine running? Or do you only have the idiot light on the dash?

[Tom Cherry]

Brad....this is one those mythical or mystical Monaco gremlins....which is probably NOTHING to worry about.  You need to do some searching here.  There are probably 10 plus topics on this and the information is unbelievable.  I, am not that well versed, on the issues...but it usually turns out to be a gremlin and Monaco made some improvements or did something to eliminate the pesky light.

Go to the search box in the upper right.  Put in ALT CHARGE.  Then click on the EVERYWHERE....a drop down will appear.  Chose Topics....  Then search.  Two pages there.  The other key word is Duvac and Topics.  Duvac is the common name for the type of "exciter" or charging circuit that Monaco used.  LOTS of discussion there and it all pertains to the pesky light.  THEN, use the same Duvac and Files.  That way you get all the information.

Typically we ask members to do the searches FIRST and not just post a topic...so try that in the future....

There will probably be a lot of comments....and such...but odds are...these are the same comments that have been made in the past few years....but the other side of the coin, for a new topic, newer members can learn and also benefit.  So, doing a search first and not posting versus posting is a mixed bag.

If you want to have the background to perhaps "comprehend" some of the more technical suggestions...then do the three searches and skim....odds are *way high" that you will see the exact question and what the answer was....

PLUS, you will learn WHEN to be concerned....  Again, this is a synopsis...but I do recall that Monaco made a wiring change later on (when?) and that eliminated the pesky flashing....was simple...but since I never had it...it didn't make the cranial hard drive.... 

2 minutes ago, Dr4Film said:

What voltage does your VOLTS gauge display with the engine running? Or do you only have the idiot light on the dash?

Good question.  Again...not the expert...but It is probably the Gremlin.  One method would be to purchase a cheap 12 VDC meter and temporarily double stick it on the dash and hook it up to an Ignition source....then drive and when the light blinks....look at the meter.  That is assuming my theory that it is a known gremlin.... and the digital gauge will give you more specific info....but that was based on an analog gauge...and you rig NOT having a Digital Volt meter...just a thought...

[BradHend]

I don’t have a physical battery guage in the cluster,  the 13.7v was an average reading from the Bluefire digital dash.  It fluctuates between 13.5 - 13.8 and is still reading in that range irregardless of the Alt. Charge light.  
@Tom Cherry I will do as requested, I sometimes forget to use the search and default to posting the questions.  I’ll try and keep that in mind more often. 😉

[Dr4Film]

Since you have no actual voltage gauge to see what voltage your alternator is putting out with the engine running, you need to hook up a DVOM to the alternator to determine what is happening.

Your alternator should be putting out over 14 VDC with the engine running.

[Tom Cherry]

8 minutes ago, Dr4Film said:

Since you have no actual voltage gauge to see what voltage your alternator is putting out with the engine running, you need to hook up a DVOM to the alternator to determine what is happening.

Your alternator should be putting out over 14 VDC with the engine running.

Richard, I agree with your comment, except trying to pin down an exact voltage on any Monaco is difficult.  As we know, when you first start up an engine and the intake heaters are on full bore, the chassis voltage will barely be 12 VDC.  Then pop back up.  I would expand the range.  My Camelot (160 Amp LN) runs in the 13.8 - 14.0 range.  Always have and I get 7 years out of my chassis batteries.

Anything above 13.6 and below 14.3 or so should be OK.  NOW, if the OP can another Cayman owner...same model year and get a reading....great.  The difference is also where you pick up the voltage.  A Power Plug is a good place.  BUT, remember, there is 40 odd feet of wire from the back to the front...so if it is being measured back there....it will be lower up front.  I have a 4/0 Chassis lug on the PCB up front...and it is fused through to the Chassis Buss.  Even that, based on the amps being pulled by the chassis components or devices up front, will have a voltage drop.

I would check the voltage at the Chassis with the engine idling....after warming up.  Then verify upfront.  You may get a bump, depending on the style of the voltage regulator...some are speed sensitive and will spike and drop back.

Just don't want Brad to have a false expectation based on your Dynasty or my Camelot.  He should easily be able to monitor it...

His Blue Fire readings are probably correct...based on the length...but I don't know where the "translator or input" readings are coming from.  A DVM or meter where you can watch the voltage and see if it changes when accelerating or turning on the HVAC Compressor or headlights is the only real test.  I THINK he is OK and it is just the Monaco Gremlin....that has worried way too many people...

[Cubflyer]

Brad,

I had a similar situation, I have a Blue Sea ML-ACR and was running my genny (with inverter charging house batteries) along with the engine running and charging the chassis batteries.  My theory is that my ML-ACR does not 'like' being in 'Auto' mode when there are two sources of charging, each charging 'their' batteries (chassis and house) and that 'messes with' the engine alternator warning light. The ML-ACR is the 'connection' between those batteries.  I now select "OFF" on my ACR when running both engines.  No glowing or blinking "ALT" light any more.  Hope this helps.   Ken

[waterskier_1]

If you are only getting 13.7 Volts at the chassis battery, it is not surprising the ALT-FAIL light is coming on.  You should have 14.2 - 14.4 Volts at the chassis battery (assuming the grid heaters are not on).  Next step is to measure the voyage at the back of the alternator.  Be careful, connect the leads with the engine off, make sure the leads are clear of any rotating devices, then start up the engine.  If this voltage is more than 0.1 - 0.2 Volts higher that the battery voltage, you have a wiring or connection issue (could be in the ground/ chassis side).  If the voltage at the back of the alternator is the same, next step would be to pull the alternator and have it checked.  Some alternators have an adjustable voltage regulator,  others it is fixed.  An alternator shop will know and can bypass the voltage regulator to determine if it is the alternator or the voltage regulator. 

  - Rick N 

[BradHend]

Thanks for the input guys.  I will be taking a closer look at things when I get home from the long weekend.  As far as I can tell all systems are operational, so @Tom Cherry may be correct and it’s not much to worry about, but I will see what I can find and report back any findings.  
Have a great long weekend everyone! Just about to throw the chicken on my fire pit grill at the Owen Sound KOA.  Fire is just about calmed down enough. 

[waterskier_1]

8 hours ago, Tom Cherry said:

 

Anything above 13.6 and below 14.3 or so should be OK.  NOW, if the OP can another Cayman owner...same model year and get a reading....great.  The difference is also where you pick up the voltage.  A Power Plug is a good place.  BUT, remember, there is 40 odd feet of wire from the back to the front...so if it is being measured back there....it will be lower up front.  I have a 4/0 Chassis lug on the PCB up front...and it is fused through to the Chassis Buss.  Even that, based on the amps being pulled by the chassis components or devices up front, will have a voltage drop.

 

Where do these parameters come from?  The alternator manufacturer?  I admit that I missed the fact that this is a Cayman, but I am not aware of any alternators designed to output only 13.6 volts.  That is typically the float voltage of a multistage charger.  But the alternator, unless you have special info on the Cayman, is not a multistage or smart charger.  All the alternators I'm familiar with for Monaco Diesel pushers have a 14.2 - 14.4 volt output specification for the voltage regulator.  Some have adjustable voltage regulators, but the manufacturer specs show it should be adjusted to 14.2 - 14.4 volts in operation (not no-load).  It could take hours for a low SOC battery to recharge at 13.6 volts.  In my opinion, notwithstanding the Cayman fact, any output less than 14.0 volts needs to be investigated.  An output below 14.0 volts will likely trigger the ALT-FAIL circuit - and this would not be a "false" trigger.  The typical "false" trigger of the ALT-FAIL circuit we talk about is on coaches built before 2007 (=/- a year) which don't have a generator disable trigger for the ALT-FAIL circuit.  In those cases, having a second charging source, typically the generator (which is turned on to provide roof air while driving down the road), but could also be caused by solar or shore power, (just not as likely to have shore power on when the main engine is running).  In the case of two or more charging sources, the alternator may attempt to reduce the voltage and can't, but in doing so the output of the alternator is so low that the ALT-FAIL circuit is triggered.  It is a "false" trigger since there really is charging going on, just not under the control of the alternator.  This is a totally different scenario than an alternator with reduced voltage output. 

  -Rick N.

[MyronTruex]

Are you running the generator at the same time?

Do you have solar panels?

With new house batteries, their happy place is likely a higher voltage than the old worn out ones. With this happy state they get full and don't pull much from a charging source.

If your batteries are being combined (via any device), while you are driving and have a second source of charging such as solar or the generator running and driving the onboard charger, you can have the alt alarm come on.

Connected to shoreline, my charging system for the batteries is charging the engine batteries as well. Starting the engine and after things calm down the alternator is blasting out its capacity and the two charging voltages collide some how and confuse the Alternator fault circuitry.

Turning on headlights often will calm things down.

Often RV's have a setup that when the generator is running and the alternator is running the battery banks are isloated from each other. This isolation does not occur when on shoreline.

In any case, as Tom suggests, you likely do not have a real problem. Just an annoyance. That's what you get for installing new batteries. 

[Tom Cherry]

2 hours ago, waterskier_1 said:

Where do these parameters come from?  The alternator manufacturer?  I admit that I missed the fact that this is a Cayman, but I am not aware of any alternators designed to output only 13.6 volts.  That is typically the float voltage of a multistage charger.  But the alternator, unless you have special info on the Cayman, is not a multistage or smart charger.  All the alternators I'm familiar with for Monaco Diesel pushers have a 14.2 - 14.4 volt output specification for the voltage regulator.  Some have adjustable voltage regulators, but the manufacturer specs show it should be adjusted to 14.2 - 14.4 volts in operation (not no-load).  It could take hours for a low SOC battery to recharge at 13.6 volts.  In my opinion, notwithstanding the Cayman fact, any output less than 14.0 volts needs to be investigated.  An output below 14.0 volts will likely trigger the ALT-FAIL circuit - and this would not be a "false" trigger.  The typical "false" trigger of the ALT-FAIL circuit we talk about is on coaches built before 2007 (=/- a year) which don't have a generator disable trigger for the ALT-FAIL circuit.  In those cases, having a second charging source, typically the generator (which is turned on to provide roof air while driving down the road), but could also be caused by solar or shore power, (just not as likely to have shore power on when the main engine is running).  In the case of two or more charging sources, the alternator may attempt to reduce the voltage and can't, but in doing so the output of the alternator is so low that the ALT-FAIL circuit is triggered.  It is a "false" trigger since there really is charging going on, just not under the control of the alternator.  This is a totally different scenario than an alternator with reduced voltage output. 

  -Rick N.

EDIT…got a picture of the “parameters” for a 2008 Dynasty with 200 Amp LN. Same ISL 425 engine as my Camelot, except mine has the 160 A LN.  the voltage from an average run (picture of the custom computer screen monitor) is 13.9 VDC.  I see 13.9 a lot…but also 13.8. This was added after first post as I got curious….

Rick,

Mine runs in the 13.8 /9 range since day one or new.  Rarely do I ever see 14.0, UNLESS I have Genny on and House is a bit low.  That kicks the Magnum into the bulk mode and I see a higher voltage on the DIC.  My DIC (Medallion LED) has a voltage as part or the main or default screen.  When the Magnum is pumping, I see about 0.2 lower reading on the DIC than on the Magnum remote…and Magnum says the values are within 10%…and I know the remote is about 0.2 VDC higher than the battery voltage. So, I know what to expect up front.

if you know the parameters for my 2008 LN (can get you the model), that would be interesting.  My comment was based on experience and what I know for a fact.  Have never had any charging issues with my system and 7 plus years out of Chassis batteries….even the OEM, since new.  My take from tinkering with all types of cars and electrical systems is that voltage is a somewhat relative term and based on the parameters of the voltage regular.  Some have “acceleration” boost circuits so it you rev up, you get a spike.  The auto industry has evolved from circa 2010 and the old “steady as she goes” voltage is a thing of the past. I see high 14.0’s on both my wife’s 2014 ATS, my 2014 Yukon and 2016 Vette.  But I also see 12.7….if fully charged.  

My comment was that i was not aware of a hard and fast MUST BE > 14 VDC….as i never see that….  And in reality as long as it is the mid to upper 13’s, we are OK.  Having a system that always pumps max and then shuts down is not good.  That is why the GM techs told me that the variable charging on my wife’s ATS was normal and that the variable charging is fairly new….which is actually a takeoff on our Magnum’s Bulk, Absorb and Float technology and has increased the life of the batteries.

So, take it as a “don’t get alarmed” if it varies.  If I used Richard’s values, then I would be worried.  His (OP) 13.7 on his BlueFire monitoring  system sounded OK to me as I probably see 13.8 a lot of the times.  From a common sense standpoint, if the system is above 13.6, I don’t sweat it.

Otherwise, I think a hard and fast “must be” is just a recipe for chasing a problem that does not exist.

That’s my take.  If i saw a low value in the low 13’s….I would check it out…but I rarely see 14.0 when driving unless the Big Boy and Generator is on. 

Hope this explains my logic and comments….

@BradHend.  My advice.  With the engine idling….I don’t think you have the VIP to go to fast idle….then put your VOM on the Chassis batteries.  Then compare to your BlueFire.  Have someone bump up to say 1300 - 1500 RPM level and check again.  That way you can correlate.  Never trust any meter until you use a high quality VOM to verify.  The front voltage will or can vary due to line loss. Now you know.  I would not sweat 13.7 unless you start getting run down batteries.  Our House floats at 13.2…so I would think that the VR would cut back…and never run or boil the battery at a constant 14.0.

May be wrong….but that’s my understanding and take….

 

[waterskier_1]

I just checked the Leece-Neville Maintenance Instructions (Form 4801-8/95) which I have on file for the 200 Amp 14 Volt, 4884JB Alternator (used with DUVAC Systems) that I have on file which was installed on my 1997 Dynasty.  

I STAND CORRECTED:  The above document states: 

• shut off all electrical asccessories
• run engine at approx 1200 RPM
• Connect voltmeter across battery terminals
• Set voltage to Manufacturer's Specifications.  Absent those, they recommend set so voltage at battery terminals is 13.8 to 14.1 volts.

I still believe that 13.7 justifies investigation.  If that is the correct value AT THE BATTERY, then it might not be high enough to satisfy the ALT-FAIL circuit.  This assumes that the generator or shore power or solar is not connected to the Chassis battery.  This might be a bad ALT-FAIL Relay, or the alternator may indeed be failing.  The ALT-FAIL Relay is the only (to the best my my knowledge) 6 VDC Relay used in our coaches.  It can be difficult to find, but when I last checked, Amazon did have them.  A good Starter - Alternator repair shop should be able to determine if the alternator (or voltage regulator) is bad or begining to fail.

Tom's advice about verifying any unknown meter with a high quality CALIBRATED meter is good.  But, even if not accurate (doesn't show the true value), as long as it is reliable (shows the same value for the same voltage over again), it can be used to monitor CHANGES in the system.  If you had been seeing 14.0 volts, and now see 13.6 volts, something is deteriorating and should be investigated. 

  -Rick N.