Forum Discussion

eric1514's avatar
eric1514
Explorer
Jul 31, 2021

Dashboard Alternator light

Hi all,

The MPPT controller on my coach will deliver 14.6 volts in bulk mode which is fine. In fact it’s exactly what the specs on my GC2 house batteries call for. But when I turn on the engine and the system connects the coach and starter batteries together, the dashboard alternator light will illuminate, presumably because Ford thinks 14.6v is to high.

Couple of questions. Do I care? As far as I know, 14.6v is not excessive and the condition should only last a couple of hours until the charger drops to absorbtion mode and a lower voltage. Or, is there an easy way to reprogram the light or turn it off completely? I’m monitoring all the batteries while I travel with an app constantly running on an old cell phone so I know what’s going on without an idiot light. I can change the profile of the charger to a different battery type and lower the voltage to 14.2v but I don’t wanna if I don’t have to.

TIA,
Eric
  • RLS7201's avatar
    RLS7201
    Explorer II
    Jul 31, 2021
    I have experienced the same issue as you. I just turn off the solar when traveling and let the alternator do it's job.

    Richard
  • BFL13's avatar
    BFL13
    Explorer II
    Jul 31, 2021
    It is not the voltage as such, but something is wrong. First try it with no solar connected to the house batts.

    Is the controller chassis grounded to the RV frame? If so disconnect that. Perhaps there is a polarity problem with how it is all wired and that is what the dash light is not liking. ( WAG) . Anyway the solar and alternator charging should play well together. Something is wrong with your wiring of the solar and the isolator outputs most likely. IMO suspect the solar installation, as the RV will be ok if as built.

    IMO don't drive around much like that until it is fixed.

    One thing to expect is that on the house batts if solar gives you 10 amps at 14.6 and alternator gives you 10 amps at 13.8 doing it one at a time, you will not get 20 amps with both on. You might get more like 10 from the solar and 5 from the alternator with its lower voltage. but that is not the issue here.
  • eric1514's avatar
    eric1514
    Explorer
    Jul 31, 2021
    Thanks all,

    If I turn off the panels, the problem goes away.

    The panels/controller work great when the engine is off.

    The controller is mounted to a piece of plywood so not grounded and the feeds from the controller go to separate buss bars, positive and negative. The positive buss has a cable that connects to the positive battery bank post and the negative buss has a cable that connects to a shunt and the shunt then connects to the batteries.

    When this happened, I just shut off the panels. My schedule hasn’t allowed me to experiment but I have a feeling that if I change the battery profile to something like GEL, the max voltage output will be 14.2. This is not my first solar install and I don’t think it’s messed up. I think it’s either a problem with the isolator or the light is showing me over voltage.

    I agree. They should play nicer together. I know I’ll have to run more tests.
  • eric1514's avatar
    eric1514
    Explorer
    Jul 31, 2021
    RLS7201 wrote:
    I have experienced the same issue as you. I just turn off the solar when traveling and let the alternator do it's job.

    Richard


    Thanks

    This works, but I put the solar up to help the alternator. I have a large battery bank and it takes a hell of a lot of driving to replace 150 or so Ahs with just the alternator.
  • BFL13's avatar
    BFL13
    Explorer II
    Jul 31, 2021
    I am guessing some mix-up in the way it is all connected where somehow the solar is opening a breaker or switch

    AFAIK the dash light does not indicate over-voltage, but indicates no charging is happening at the engine battery. With the light on, you could check the engine battery's voltage, turning the headlights on.

    Do you also have a dash switch for using the house batts to start the engine? My class C does not, only has the isolator with ignition run to it. Some have a three switch affair for that, where the run circuit to the isolator gets there a different way. Don't know if that could be in backwards.

    Maybe something is on a buss that shouldn't be with the others on it.
  • eric1514's avatar
    eric1514
    Explorer
    Jul 31, 2021
    I have a boost switch, but I’m not sure it’s wired correctly. I’m not the original owner. I have noticed when I push the boost button, the relay doesn’t click.

    That’s a good clue, thanks. I think I’ll disconnect the switch entirely and see what happens, but it may be a while until I get the chance.

    Are you 100% sure the light does not indicate an overcharge? That was my first guess.

    Thanks,
    Eric
  • theoldwizard1's avatar
    theoldwizard1
    Explorer II
    Jul 31, 2021
    eric1514 wrote:
    ... presumably because Ford thinks 14.6v is to high.

    Couple of questions. Do I care? As far as I know, 14.6v is not excessive and the condition should only last a couple of hours until the charger drops to absorbtion mode and a lower voltage.

    Actually the PCM controls the voltage and yes, 14.6V is too high.

    First, confirm the voltage at the vehicle battery with the trailer and solar. Now disconnect the trailer. I'll bet it is about 13.2V.

    High voltage will shorten the vehicle battery life.
  • BFL13's avatar
    BFL13
    Explorer II
    Jul 31, 2021
    Not 100% sure, but 14.6 is not over-voltage. It will be about that at first and then taper once you get going and it all warms up, riding around 14 or a bit under that. IMO with that light on with the solar on, check the engine batt's voltage with your multimeter to see if it is getting any charging at all.

    If not, then you can't drive very far like that.

    Drew E on here would know about all to do with booster switches and run circuits etc. Others too.
  • eric1514's avatar
    eric1514
    Explorer
    Jul 31, 2021
    I monitored all the goings on with a Victron 712 that was showing me chassis and house battery voltage at the same time. All I know is that both battery banks were receiving positive voltage. I didn’t think at the time to record any numbers. I just pulled over and turned off the panels. This was my first drive after installing them.

    I really need to do more testing.

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