Community Forums

FW · 04-25-2013, 12:33 AM

A 2000 Monaco 36' with 275hp 5.9l ISB engine and MH3060 transmission,
what would cause my dash voltmeter to fluctuate from 13.8 to 14.5 at all
engine operating speeds?
At a truck/rv service center with a Snap-on (battery/starter/alternator) tester, these systems passed.
Thanks

J Walker · 04-25-2013, 10:48 AM

Troubleshooting requires that you break the problem down. If you have a Silverleaf VMSpc you can read the information directly from the ECM and transmission module. If that looks ok then you have a problem in the dash data unit or gauge.

BFlinn181 · 04-25-2013, 11:08 AM

Are all battery terminals and connections clean and tight? How about ground connections? That's were I'd start. Also check ground connection to gauge cluster. Hooking up a second voltmeter will help determine if your gauge is at fault.

FW · 04-25-2013, 12:10 PM

No Silverleaf.
All battery connections clean and tight.
My digital voltmeter says alternator putting out 14.2 at idle.
Dash voltmeter is analog.
Will check dash grounds.
Thanks
Frank

sc3283 · 04-25-2013, 09:35 PM

is your inverter on when this occurs? If so are you using large 110v AC loads when the fluctuation occurs?

FW · 04-25-2013, 11:12 PM

Hi; Inverter is always on. Only load is refer (Norcold 1200lrim) sometimes on LP/sometimes on AC from inverter. Will see what happens without inverter in a few days.
Some times generator is used for cooling purposes with both air conditioners
on, but mostly generator is not on.
I know that there is a grid heater that sucks voltage when it is cold, but that is a slow moving voltage change (voltage drops to 12 for a couple seconds and then goes back to 14.5), not like the quick and continuous motion I have.
Frank

EngineerMike · 04-25-2013, 11:35 PM

If you get to a place you can do some work on it, take the alternator to a local parts shop that can test it. I think its going bad. the "drops to 12 for a couple seconds then..." is what sounds like failing alternator.
On many rigs if you crank up the gen and run the charger, you can still drive the rig w/a bad alternator, but it may take a delay of a minute or so before all the lags are over to see the higher voltage on the dash. This assumes you have a BIRD or other way to connect the chassis batteries to the gen powering the charger charging the house. If push comes to shove you can use the old timey method of jumper cables or make up jumpers to bolt in while driving.

FW · 04-26-2013, 12:09 AM

Hi; The grid heater that heats the incoming air turns on for a couple seconds and then off and repeats until engine temp has risen to an unknown to me predetermined level.
Frank

Hooligan · 04-26-2013, 08:02 PM

3/4 volt change is not much.
My grid heater drops the voltage by 3-4 volts, only small fluctuations (less than a volt) are my turn signals, flashers or an alarm).
WAG- Is it a constant cycle like an alarm or flasher trying to activate??. Does your digital voltmeter fluctuate at the same time as the analog in the dash..

Coaster1 · 04-27-2013, 09:02 AM

I believe that the regulator is internal on the alternator, could be that.

NMBeemercouple · 04-27-2013, 11:36 AM

I'm having the same problems now. Have taken the rig into a shop that tests and rebuilds the alternator. They can't get to it till Monday, so will relay what happened with mine, not that it is the identical case as yours, but I have same symptoms now. Voltmeter is jumping (pulsing) even the headlights are affected. To keep the Alternator dash warning light from coming on as it spikes over 14 volts, we keep a load on with headlights.

Good luck with yours.

Leroy

Iron Man · 04-30-2013, 10:20 AM

Check to see if you guage information comes from the ECM. If they do check the ground and the power connector at the ECM. I had problem with low voltage at the guage everywhere else was showint 14.0 vots with engine running. Traced it back to a bad voltage connector at the ECM. VMSPEC confirmed that the ECM was reporting the low voltage.

FW · 05-24-2013, 02:04 PM

Sorry this took so long. I have been staying in campgrounds that prohibit maintenance on the premises. I checked voltage at batteries while idling (750) and at high idle speed (1100), voltage was a steady 14.8 with my digital voltmeter. As I drove to next campground I thought about my solar panel and trick-l-start connections and removed them before rechecking alternator output. Output was pulsating at the batteries just like before. I guess I will have to go to shop and have alternator pulled and check/fixed.
I checked all grounds I could find/get to. All solid and clean.