Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 06, 2025 ...

generator again!

June 03, 2010, 09:25:19 pm

I am really ticked over this generator issue.  I was losing power (though generator never stalled) whenever a load was removed.  Took it to Onan and they said the generator was good but that the transfer switch was bad.  Replaced the transfer switch and now I lose power when applying a load (or at least the 2nd air conditioner).  When I turn it on it bogs and sometimes catches back up and sometimes drops out and I have to run and turn both air conditioners off cause if I don't, after the 30 second delay is up the power tries to come back and the new transfer switch chatters and drops out again.  I guess it is back to Cummins/Onan for me.  At this point I'm guessing the old ATS was fine and I have an undiagnosed generator problem (though the engine itself sounds great).  Voltage regulator I'm guessing.  It seems odd that the old ATS clicked off when taking the load away and the new ATS is doing it when adding to the load.  I checked the voltage at an outlet and it never drops below 110 even when bogging down.  One curious thing I noticed from the install instructions on the ATS: it said that it must be ground ed to the chassis but the old unit had the ground wires from the generator, the shorepower and the wire to the coach all connected to the grounding block but no other ground wire is present and the unit itself is sitting on a rubber mat under the end of the bed.  I wired the new one just like the old one and it works great on shorepower.

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Re: generator again!

Reply #1 – June 03, 2010, 10:40:42 pm

Have them check the speed regulator/governor.

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Re: generator again!

Reply #2 – June 05, 2010, 09:55:16 pm

Regarding the generator issues, having had a bad capacitor in a air conditioner making the same sort of
happenings as you describe.
IF you have a peak amp meter, you can see what the starting amp load is, first on a good air conditioner and compare with a suspected bad one.
Everyone yells generator when SOME times it is another issue, have seen a breaker trip on the panel when the commercial power could not start it (air conditioner) either.
Having the Cummins/Onan shop figure it out for you can get a little costly. 
Having good data upon arrival at the shop can save you a nice chunk.
Good luck
Dave M

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Reply #3 – June 06, 2010, 12:47:15 am

Had our company's chief engineer over again today to finish the dash air as relay came in.  Works good but a slow leak is suspected though couldn't find it with the sniffer.  I'll take refill cans with me.  He looked over the generator again and the darned thing would drop out.  It was doing it about 50% of the time Friday.  We did try starting and stopping the units in rotation for just the reason you mentioned.  The only thing I can think of is that today it had been run heavily just the day before and when I had it an Cummins/Onan, the tech told me he cranked it up and let it run about an hour before attempting to duplicate the problem.  I just find it odd that it was dropping out when taking load off until I swapped out the ATS, and now I can remove load without a problem...but adding load is another story.  I guess I'll just baby it.  Let it run 15 min. before attempting to add load and give it 5 minutes or so before attempting to add more.  The only change I made to the electrical system prior to this all happening was a new converter/charger.  I can't see how that could cause any of this. 

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Reply #4 – June 06, 2010, 08:31:38 am

Dwayne, Could you give me the model and spec info from that onan ?  I can get into it, drawings etc, see what could be happening.
Dave M

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Reply #5 – June 06, 2010, 12:06:10 pm

Dwayne;
I seem tohave had mind in a stinky place. On your Fridge---- Have the propane pressure regulator checked.
I installed a new cooling unit severral years ago in my SOB coach. 1st trip out ( running on propane ) it did not cool great. But when camped in with electric it cooled great over night. Stoped in AMA 2 RV shop, told the service man ( also the owner) my problems. I pulled the unit into his shed, adjusted to propane pressure. It worked ggreat for 6 more years.
Why I didn't recoginise it till just now? @ 77, it takes the mind awhile !!

bill Chaplin

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Reply #6 – June 07, 2010, 07:29:12 pm

Bill,
My fridge reaches the same temps on AC or propane.  The behind the fridge fan gets me a few degrees cooler.  The inside frindge fan (battery operated) gets me a few more.  Combined I'm within acceptable range so I guess that is what I'll have to do.  As for the generator.  What a nightmare.  Our Ch. Engineer tested it Saturday and it worked fine.  Today I checked it again (as I have an appointment in the morning to take it back to Cummins/Onan and wanted to be sure as I'm about to take this rig to Las Vegas and back.  I'm so frustrated.  I can keep it from causing the ATS to switch off if I keep the engine adjusted so that it is racing.  If I put the adjustment back where it was, the governor kicks in but half the time the second air conditioner coming on causes the engine to shutter and the power kicks off.  The engine never stalls.  Guess it is back to Onan.

WG4T:  here is the info on the generator.  Mine is the second one listed under models:

http://www.cumminsbridgeway.com/Products/Used/UsedSpecSheets/emerald6500.pdf

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Reply #7 – June 09, 2010, 02:16:31 pm

Cummins insists the generator is fine.  The tech thinks that one or both of the A/C units are pulling more power on start-up than they should or used to although they didn't put a meter on them.  I've tried shutting everything else down (at breaker box) and starting them, mixing up the order.  I've also tried starting them without the compressor and turning the thermostat until it kicks on.  It doesn't seem to matter the order or the method but once in a while the rear A/C all by itself will cause the generator to bog and the transfer switch to open so I assume this one is the culprit.  He told me that I should probably replace them but that I could buy some time by installing a hard start capacitor.  Apparently people with small campers and a small generator will try to add an A/C unit but the generator just can't handle it, at least on start-up.  This cheap mod allows them to have A/C.  Doing the same thing on my units should offset the power surge on start-up and stop the transfer switch from openning.  It is worth a few bucks to experiment with it.  I hate the idea of replacing an A/C unit that blows cold enough to hang meat.  I did a little research and some people claim that this mod reduced the life of the compressor big time.  But if it is sucking up all the power the generator can put out...how much longer does it have anyway?  Has anyone heard of this mod or installed one?   

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Reply #8 – June 09, 2010, 06:46:02 pm

Dwayne, Did the Onan tech actually put a load bank on your generator or did he just start it up and claim it was fine from the sound of it ?
He certainly should have a peak reading amp meter to check the starting load of each air conditioner.
At the same time when checking the peak amp draw on starting, should also use a min/max reading volt meter to check the actual voltage swing during the starting cycle.

As for looking at the sales lit of your generator does not tell me very much, there are toooooo many variations, why the ACTUAL model and SPEC info is important.
I think I got ab email from you but my spam filter killed it.
FWIW
Dave M Va

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Reply #9 – June 09, 2010, 11:41:45 pm

Dwayne,

It sounds like the compressor may have high head pressure or some other issue making it hard to start.  Are your A/C units Coleman?  My Colemans are sealed units and yours probably are also but they make valves that will puncture the lines so that the freon level can be checked.  It sounds like your chief engineer could check out your roof A/C's for starting current, voltage drop, etc.  If you had to have an RV shop check them out it might be cheaper just to replace the hard starting unit.  Our units cool very well but are quite noisy even on low fan, I wish I could afford to replace them with more modern units.

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Reply #10 – June 10, 2010, 12:26:13 am

They are Coleman TSR units probably original.  Cummins/Onan checked generator function only and did not check A/C units but are certain that one or both has problems.  They put some kind of load on it with the A/C off and it responded appropriately.  I know it isn't head pressure cause I warmed up the generator for 30 min. before starting the A/C after both units having been off for days and immediately it puked out.  It will always react to the 2nd A/C and sometimes it bogs but recovers before the switch opens.  Sometimes not.  Didn't used to act this way at all.  To me it seems like whatever it is that calls for more revs when given a load isn't responding quick enough but they say it is doing what it is supposed to do and it sure sounds like it is running just fine.  They told me they had a similar situation where the owner eventually discovered that an A/C unit was maintaining too much head pressure for an hour after the compresser went off.  I find that hard to believe.  If the hard start capacitor modification doesn't work...I guess I'm just living with it.  It sure doesn't seem like too much to ask to have a generator handle turning a couple of A/C units on and off reliably.

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Reply #11 – June 10, 2010, 08:20:10 am

I would take the shroud off the AC Unit and physically check to see that the fan shaft turns freely and that it is not impinging on anything that would retard it.  You already know that these AC motors should not be that hard to start.
On an older unit once I had a fan shaft that had frozen up due to corrosion over the winter, it would growl before it would start to rotate. a lot of PB Blaster freed it up.
Good luck

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Reply #12 – June 11, 2010, 10:27:44 pm

Garry,

Generally the fan motor does not draw that much current.  The real current draw is the compressor trying to compress the freon gas.  At least in mine the fan stalling because of gunked up bearings did not seem to have an affect on the current draw/voltage.

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