Curious Fridge behavior

[172av8r]

I had an interesting problem posed to me this weekend. While the problem was not mine, in the interest of my own learning as well as the others in the group, I thought I'd pose it here.

While camping this weekend in my Roo, another Roo pulled into the spot next to me. Later that day, the owner came over to my site, and asked that, since I also had a Roo, could I help him with a problem he is having.

Turns out his is a new-to-him 2005 camper, purchased end of last season. This was his first time using it, and his first time out ever with an RV.

All the lights in his camper were getting progressively dimmer, and his fridge wouldn't work. I suspected he had a problem with his converter and/or battery. We checked fuses etc. and all were good. But the weird one for me was his Fridge.. He was plugged into 120v shore power. But when he turned on the fridge, the check light came on instantly, even though the fridge was set to auto.

The next day, he went to Wally world and got a new battery. Hooked it up, and voila, everything worked great again, including the fridge.

So the part that I am wondering about is why the fridge wouldn't work on 120? Does it also require 12v from the converter / battery to work on shore power?

Incidentally, I still think he has a problem with his converter, as after a day with the new battery, the voltmeter showed the battery at 2/3, even though he was plugged into shore power. I informed him of this, and so he'll get it checked after his trip. But the fridge thing is making me question my understanding of its operation.

Thoughts? Comments?

[007matman]

From what I understand, 12v is needed to run the gas valve. That's why the fridge will shut off if it's running on gas and the battery dies.

The new battery will take some time to recharge off of shore power. That sounds like a long time even by that standard though. I would suspect something there as well. I'm sure it could be tested to verify.

[172av8r]

Originally Posted by 007matman

From what I understand, 12v is needed to run the gas valve. That's why the fridge will shut off if it's running on gas and the battery dies.

I understand it needs 12v to run on gas. But this was on shore power. (switch set to Auto, not gas).

[DaveJordan]

I'm not absolutely certain, but I believe that the fridge has a 12 volt control board - no 12 volt, no control. That being said, one has to wonder why the converter wasn't supplying 12 volts when he was plugged in. Seems like that should work even if the battery is failing...

Dave

[007matman]

Originally Posted by DaveJordan

I'm not absolutely certain, but I believe that the fridge has a 12 volt control board - no 12 volt, no control. That being said, one has to wonder why the converter wasn't supplying 12 volts when he was plugged in. Seems like that should work even if the battery is failing...

Dave

Agreed. Or even without a battery I would think.

His lights are 12v and they're working though. I wonder if there is another fuse in there. I know when I pulled out my inverter/wiring panel last weekend there were a few 12v fuses hanging back there in line on the wires. I didn't trace them to see where they went but it would be feasible that one of them could've connected to the fridge. Might be worth pulling that out (as well as the fridge) and taking a peek behind there.

[TheGerman]

Originally Posted by 172av8r

Incidentally, I still think he has a problem with his converter, as after a day with the new battery, the voltmeter showed the battery at 2/3, even though he was plugged into shore power. I informed him of this, and so he'll get it checked after his trip. But the fridge thing is making me question my understanding of its operation.

Sounds like he was running on battery all the time. Did you/he actually *check* any of the 120V outlets ? My first step would be to see if there's 120V present. If yes then there is a problem with the converter.

The fridge needs 12V (or actually at least 8V something) to work on gas or electric. The check light coming on is an indication there was some power getting to it. Assuming 120V was not present then it would try to run on gas, which would require gas turned on and enough power for the ignitor to work.

[Pinn]

Really stupid question here.. was the breaker at the power pole turned on??
A lot of places I go will have them turned off when I arrive.

[172av8r]

Yes, all the breakers were on and 120v present. Microwave, A/C, etc all were functional. Which is why I didn't understand the fridge not working.

I think I now understand from the comments here that the fridge uses 12v too, even on shore power. So in his case, I believe the converter is bad, he was running on battery only, and when the battery dropped below some voltage (which it clearly had because all the lights were very dim), then the fridge won't turn on, even with 120v to it. This is something I did not know before (that the fridge needed 12v also, even on shore power)

Another lesson I learned.. keep a multimeter in my trailer's toolkit. It would've made some of the troubleshooting a lot easier!

[Bama Rambler]

The fridge needs 12 volt power to power the control board even when running on 120 volt power. All the 120 volt power really does is power the electric element. 12 volt power still does all the control. And since it doesn't make it's own control power that comes from the onboard battery/converter.

[5picker]

Originally Posted by Bama Rambler

The fridge needs 12 volt power to power the control board even when running on 120 volt power. All the 120 volt power really does is power the electric element. 12 volt power still does all the control. And since it doesn't make it's own control power that comes from the onboard battery/converter.

Correct.
And I suspect his onboard converter/charger is bad as you mentioned even plugged in to shore power, the lights were getting dimmer and after they replaced the battery, it too was going dead.