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artdeco · 10-15-2021, 10:14 AM

We are at an RV park in TN and had a repairman fixing the front slide because something was causing it to come in strangely, the seal was hanging loose at front and there was some gunk at the top of the slide. So the slide got fixed but now the engine won't start. We had the engine checked out and serviced at Cummins in June. Repairman checked the "engine won't start flow chart" and found the battery isolator was very hot. Would appreciate any ideas what to do next. Thanks.

Xmcdog · 10-15-2021, 10:25 AM

Sounds like a bad contact on the battery isolator.

windsorbill · 10-15-2021, 10:29 AM

Quote:

Originally Posted by artdeco

We are at an RV park in TN and had a repairman fixing the front slide because something was causing it to come in strangely, the seal was hanging loose at front and there was some gunk at the top of the slide. So the slide got fixed but now the engine won't start. We had the engine checked out and serviced at Cummins in June. Repairman checked the "engine won't start flow chart" and found the battery isolator was very hot. Would appreciate any ideas what to do next. Thanks.

elaborate on 'It won't start'.

Does engine turn over but doesn't start, or does it not even turn over???

twinboat · 10-15-2021, 11:01 AM

The isolator solenoid will be hot if on shore power. It's engaged so that the chassis battery is charging thru the house charging system.

Many systems will lockout the engine starting if the slides are out. Since that's where he worked, he should be looking for a lockout switch and wiring around the slide.

artdeco · 10-15-2021, 11:50 AM

Thanks for the replies. Completely odd thing that caused the problem: repair guy's helper measured to cut a plexiglass cover for the one that was missing over the rear run box and he must have touched a switch labelled "rear" in the top left side of the box. Once found, problem solved. Engine started. Apparently that switch can start the engine from the rear. I guess it would need the key to be in the ignition and it wasn't,t when the helper touched it.

Windsor - the engine was just dead, not a sound. We suspected it was some connection because we had had the engine checked out and there's been no problem this past month of driving most every day.

twin boat - that is good to know about the isolator. Its always good to know that something is normal.

jacwjames · 10-15-2021, 12:17 PM

Yup, the rear start issue comes up about every 3-4 months.

I've had it happen to me twice when I hit it while checking something in the engine compartment. First time took some time to figure out. Second time it was quicker.

Just something you have to remember.

twinboat · 10-15-2021, 03:00 PM

Quote:

Originally Posted by artdeco

Thanks for the replies. Completely odd thing that caused the problem: repair guy's helper measured to cut a plexiglass cover for the one that was missing over the rear run box and he must have touched a switch labelled "rear" in the top left side of the box. Once found, problem solved. Engine started. Apparently that switch can start the engine from the rear. I guess it would need the key to be in the ignition and it wasn't,t when the helper touched it.

Windsor - the engine was just dead, not a sound. We suspected it was some connection because we had had the engine checked out and there's been no problem this past month of driving most every day.

twin boat - that is good to know about the isolator. Its always good to know that something is normal.

Always look where the last guy worked, even if it was you.

Outbound · 10-15-2021, 04:29 PM

Good advice

artdeco · 10-15-2021, 06:09 PM

I think I'll frame that in big letters "Always look where the last guy worked, even if it was you."

Thanks all!

153stars · 10-15-2021, 07:13 PM

That's also why it can be a good idea not to attack too many things at once without a shakedown in between. Less steps to backtrack.

Quote:

Originally Posted by artdeco

I think I'll frame that in big letters "Always look where the last guy worked, even if it was you."

Thanks all!

rpasetto · 10-16-2021, 09:08 AM

Regarding the BigBoy, "isolator" solenoid. It can be taken apart, contacts cleaned, and reassembled. There's a document on the procedure somewhere (either here on on the Monacoers site if your in that forum).

There's also a thread on replacing the Big Boy with a Blue Sea ML-ACR, probably in both places.

artdeco · 10-16-2021, 11:17 AM

Thanks, Rick. I will look into it. The repair guy yesterday said that battery isolator was very hot.

artdeco · 10-16-2021, 11:25 AM

153stars, that's a good idea and in this instance it was the owner of the repair shop and his helper. So more chances for a mistake.

nehog · 10-19-2021, 04:34 PM

Quote:

Originally Posted by twinboat

The isolator solenoid will be hot if on shore power. It's engaged so that the chassis battery is charging thru the house charging system.

Many systems will lockout the engine starting if the slides are out. Since that's where he worked, he should be looking for a lockout switch and wiring around the slide.

Uh, no not on the Holiday Rambler I own, and not on any I know of. That isolator is to charge the house batteries while the engine is running, not the other way around. If you want the chassis batteries to charge when plugged into shore power you have to install a separate battery charger...

Why the OP's isolator is getting hot is something that he has to do diagnostics on.