electrical enigma

I have a 1991 Foretravel Grandvilla. Has been doing great but recently after a pretty severe storm I began to have the following problems. I think they are relative to the battery isolator.
1. Generator will not start but can here it click when start is pushed.
2. Refrigerator not cooling correctly. I dont think the 12v is getting to it.
3. Unit has boost SWITCH which when on will engage both house and engine battery to start engine and or generator, it bypasses the isolator I believe. This is not coming on.

I have checked all fuses, breakers that I can find and all appear to be ok. I wonder if it is the isolator solenoid but dont know how to check it?

Engine starts without problems and once on camp power the whole unit except the fridge does just fine.

Any thoughts, and how do i check the isolator solenoid.?..Thanks...Dr.G


Senior Member
Re: electrical enigma

#1 sounds as though your coach battery is discharged, or is in poor condition and will not hold a charge.

#2 tends to support that if you are not connected to shore power. If you have shore power, the converter should supply enough voltage to operate the refrigerator and all 12V appliances with no battery help. If your inside lights do not work or are dim, that would also indicate the same problems.

#3 depends upon just how the boost is wired. In some cases it is intended only to boost the chassis battery. The way that it works is the switch operates a 12V relay that connects the two battery systems together. If the chassis battery is discharged and it happens to be the only source of power for the boost realy, then you would have that very problem.

Try this. First, start the chassis engine and allow it to operate for a few minutes. It would be well to do so at a "fast idle" condition to increase the output of the engine alternator. Once it is operating for a while it will supply 12V power to the coach side in an attempt to charge the coach battery. With the chassis engine running, hold down the boost switch and it should now close. With that switch held down, try starting the genset. Most likely it will now crank.
Re: electrical enigma

Thanks Kirk. I tried running the engine at relatively high idle and then turned boost on. It made no difference. Have checked both batteries independently and they are both at full charge. Am stumped ? Doc.
RE: electrical enigma

Fridge is running fine. Boost switch still not coming on. When I check voltage at genset it is good. When I try to turn Genset on the starter solenoid clicks. Is there a way to know if this solenoid is bad. It is apparent that juice is not getting through to start the generator but for what reason?..Help. I am plugged into shoreline...Doc


Senior Member
Re: electrical enigma

This does not sound like it has any connection to the boost switch. You could very easily be sure by simply using a set of jumper cables and another vehicle, as you would to start the chassis, but I am thinking that it won't change anything. If you have not done so, remove and clean all of the battery cables to make sure that the connections are good. You can check to be sure that the battery is supplying power to the 12V systems by disconnecting shore power. If the lights and water pump still work with shore power off and the chassis engine not running, then you will know that there is nothing preventing power from leaving the coach battery. Why are you so sure that the boost switch is not working? If the coach battery is properly charged, the use of it would change nothing. The only way to know for sure is to locate the solenoid part and actually check it with a meter while energized. There are several different locations that coach builders put them and I don't know the practice of Foretravel. In our Cruise Master, it is in a box that is mounted on the firewall, in front of the engine and above the radiator, along with the battery isolator, and several other such items. I have also seen them mounted on one of the frame rails of motorhomes, up under the RV. You should be able to locate it by tracing the battery cables. The fact that the start solenoid of the genset does click tends to say that the battery is connected properly, but it is either not supplying enough current, or the starter has failed. Cleaning the battery cables might help as a high resistance connection would limit the current flow and have a much greater effect on the starting current than on the small current that lights use.

If that does not work, the next thing would be to find a clamp on amp meter to test to see what the current flow is when you engage the starter. If it is normal or greater, that would mean a problem with the starter and not the power supply.
Re: electrical enigma

Will try these things. As for the boost, the RV manual states that the boost will send juice directly to the engine and or generator when it is engaged. I have found all the isolators, solenoids, inverters and converters and boy they put some of these things in the dardest places. The isolator solenoid is on the engine firewall anterior to and above the RV leveling system. Thanks for the help. Ill let ya know. Doc
Re: electrical enigma

If you have a weak cell in your battery it will show 12 volts but will not have thae amperage to crank the genset. Also sounds like your solenoid is bad so check both. Also starter at genset may be bad.
Re: electrical enigma

HMMMMMM after a storm. Wanna bet you have a corroded connection somewhere. A little dampness in the wrong place can reek havic with a battery system


Senior Member
Re: electrical enigma

I painted my roof (alum kind) with the Kool Seal (three coats so far) after using their caulking on all seams. Also, replaced the seal on the roof A/C unit, and sealed in the front running lights. Last couple of summers, when I would leave for South, I'd get about a cup or two of water inside the MH on the inside of the front windshield when I first headed down the driveway. Thought it might be some small pinholes in the alum roof that was seeping in some moisture. Had roof / RV covered this summer hoping that would also help. Uncovered it three weeks ago to do the painting, etc. Well, it rained hard the last few days, and darned if I did not have some water leaking in the back bedroom in the corner (on the side where the MH is just a tad unlevel (leans about an inch that way)). I'm getting stumped again on this issue. Guess I'll seal the rear top running lights and there is a seam that connects the back of the MH to the main part of the MH that I'll take the filler out and put in some sealer under it and put the cover back on it. If this doesn't work, I'm totally at a loss... :dead:
Sorry to get a little off track here, but point is, water coming inside a MH can run to many different areas, no matter where it comes in), including electrical areas, so it is possible that you may have some water leaking that has caused some corrosion somewhere...... ;) :(