Trouble with Shore vs Gen power

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MonicaM

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Nov 12, 2012
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3
Hi Everyone,
We just got a "new to us" 2008 Heartland Toyhauler.  This is our first with an onboard generator (onan cummins 5500) so please forgive our ignorance on this stuff.  Here is the sequence of events that I am trying to piece together to diagnose the issue and could really use help from more experienced folks out there!!

Took it out for the first time this past weekend.  Plugged into shore power Friday night and everything worked fine all weekend, even ran both AC's.  On Sunday when we were packing up, I started bringing the slides back in and in the middle of it, heard a long beep and then lights started dimming.  It became apparent we were then on battery power.  We couldn't figure out why the shore power wasn't working.  We cranked up generator but the batteries were too weak to help it start.  We plugged into the truck and finally the gen started up.  We were then able to bring in slides.  What I can't remember is if we were still connected to the truck when we brought in the slides....I assumed the gen was providing power and maybe they camp shut off shore power??? It was late in the day and we just trying to get home.  So, once we got it home, I started up the gen, let out the slides and started cleaning.  After a while I noticed the lights were not very bright.  It became apparent, even though the gen was running, we weren't getting power from the gen.  So now, power from shore and gen don't seem to be working.  Only power from plug to truck.  What are we doing wrong?  Checked breaker on generator, flipped off and on.  Any ideas?

On last tidbit.  Just went to try to trouble shoot it again.  Gen started ok.  Let the slides out and just a few minutes later, tried to pull them back in.  Gen still was running, but lights were getting dim. When I would let go of slide switch lights got brighter (of course) but seemed to be slowly dimming??  Hit the slide switch again and gen sputtered then quit.  I'm perplexed!
 

Lou Schneider

Site Team
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Mar 14, 2005
Posts
10,954
Hi Monica - welcome to The RV Forum!

The generator doesn't produce 12 volts - like shore power, it sends 120 volts AC to the converter, which then makes 12 volts to charge the batteries and run the lights.

The slide can run either on battery power, or on 12 volts from the converter.  It sounds like you tripped a breaker or fuse on the converter, so it's no longer working.

You may have lost shore power at the campground some time before you ran the slide in, and between any lights you used after that time and the heavy load of the slide motor the batteries ran down enough to trip the low voltage alarm as you ran in the slide.  When you started the generator the converter saw 120 volts and came came back on line, but the combined load of trying to charge deeply discharged batteries and also providing current to operate the slide motor blew a fuse, taking the converter off line.

Driving home the charging wire from the truck recharged the batteries, but without any help from the converter they just ran down again when you got home.

Check the 12 volt fuses you can see in the electrical panel - if none of them are blown, sometimes there's a pair of fuses on the converter itself.  If you can locate the converter and tell us it's make and model we can probably point you further in the right direction.
 

Alfa38User

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Oct 4, 2007
Posts
6,676
Your slides work on 12V (battery) power. If the converter was not putting out 12V and charging the batteries then this is exactly what would happen. The converter operates on 120V from either the camp ground power when plugged in or by the  generator when it is operating and produces 120V.

It sounds like, for 1 reason or another, the converter is not functioning correctly,  it was not getting 120V from either source although during the weekend itself, everything was functioning ok. I am not familiar with a generator as found in a trailer but suspect it is very similar to a motorhome so equipped. The 120V is normally switched from 1 source to the other using an Automatic Transfer Switch (ATS) (unless you have to move the power cord to do so manually).

I suspect that this switch is acting up as this is the only common part between the shore power and generator connections. The contactors (big relays) are not operating, the contacts have been burned, or the generator is not producing power.

One way this happens frequently is by not removing loads (like AC units) before switching back and forth.
 

MonicaM

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Nov 12, 2012
Posts
3
Thanks so much for the replies!  Will check on the fuses.  Any ideas where I may be able to find the converter to check the fuses on it?  Is it near the generator?
 

MonicaM

New member
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Nov 12, 2012
Posts
3
Thanks so much for the replies.  This is very helpful!!!  Lou, your suggestion about the converter sounds plausible.  I did find the breaker for the converter in the breakerbox.  It did not appear tripped but I flipped it off then on anyway.  Lou, you said to check the 12v fuses.  In the fuse box there were fuses for everything, appliances, slides, etc.  I only found 1 that said 12v outlet and it did not appear be blown.  Do I need to check them all?  Any hints on where to find the converter and I can try those fuses too.

Alfa, I also think you may be onto something with the transfer switch.  If the converter had a blown fuse, could it have caused the ATS to not work?

 

John From Detroit

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Apr 12, 2005
Posts
24,944
Location
Davison Michigan
Where to find suspect #1 (The converter).. Well, they can put them anywhere.. On mine it is in one of the most illogical places it can be (As far from the batteries as is possible).  IF you have a single door or hatch behind which you find both 12 volt fuses and 120 volt breakers (NOTE, if you open a cabinet, and there are TWO boxes inside the cabinet this is not the case) The odds are fairly high the converter is the back side of that very box.. Give us the make and model on the door and we can tell you for sure.

IF like me you have a 12 volt fuse box, and a seperate 120 volt breaker box, the converter is likely elsewhere.

ONE problem with some comverters (MINE for example) is that they plug in,,,, and I have been known to accidently snag the cord and unplug it.. One of the less expensive fixes :).
 

Alfa38User

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Oct 4, 2007
Posts
6,676
Alfa, I also think you may be onto something with the transfer switch.  If the converter had a blown fuse, could it have caused the ATS to not work?

No, the switch is controlled by the generator control circuit, I believe. There is a built-in short time delay to allow the generator to get up to speed and then the switch will operate.
 

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