Residential fridge question

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clockdrfla

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Ocala, Florida
I have an Open Range 5th wheel with a residential fridge.  The fridge is shutting off after about 4-5 hours of highway traveling.  Inverter is ok and both batteries are new.  I thought that as long as bed plug was connected to 5th wheel and truck is running, rv batteries would stay charged and would keep fridge running.  Is there an inline switch or fuse in the truck that could be bad?  What do I need to check?  Thanks
 
clockdrfla said:
I have an Open Range 5th wheel with a residential fridge.  The fridge is shutting off after about 4-5 hours of highway traveling.  Inverter is ok and both batteries are new.  I thought that as long as bed plug was connected to 5th wheel and truck is running, rv batteries would stay charged and would keep fridge running.  Is there an inline switch or fuse in the truck that could be bad?  What do I need to check?  Thanks
Click to expand...

There's one pin in your receptacle that has to be hot while traveling. That's what keeps the battery charged. Check it out. Sometimes the truck has to be running for it to get power. There may be a fuse missing from the factory.
Looking at the receptacle of the tow vehicle, It is the one at 1:00 o'clock #4. The one on the the opposite side (7 o'clock #1) is the ground.

https://www.etrailer.com/question-363.html
 
You didn't mention the truck year/make/model, but yes, your truck very likely has a fuse or breaker for the trailer 12v line.  Trucks usually come without a fuse installed for that, so yours may never have supplied power to the trailer that way. The truck owner manual should tell you what fuse and where it is located.

You can test for +12v at the trailer pin using any VOM (as little as $5 at Harbor Freight if you don't have one). I've attached a diagram of the trailer plug to show wgere to test.
 

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Gary RV_Wizard said:
You didn't mention the truck year/make/model, but yes, your truck very likely has a fuse or breaker for the trailer 12v line.  Trucks usually come without a fuse installed for that, so yours may never have supplied power to the trailer that way. The truck owner manual should tell you what fuse and where it is located.

You can test for +12v at the trailer pin using any VOM (as little as $5 at Harbor Freight if you don't have one). I've attached a diagram of the trailer plug to show wgere to test.
Click to expand...
Truck is a 2008 GMC Sierra SLE 2500 HD diesel
 
I'm pretty sure that year & model has a fuse for the 12v power to the trailer plug, but it sort of depends on who wired the plug as well. Anyway, start by testing the plug +12v pin and go from there.
 
You might also get an inexpensive volt-ohm-meter and check the voltage at your truck plug.  I believe Tow Vehicle wiring can keep charged batteries up, but in many cases I kind of doubt that it provides enough power to charge from a discharged state, or to keep charge up against a fairly heavy load. 

First, it seems like once the TV batteries are recharged from starting the engine, the TV voltage regulator will drop the voltage down to a maintenance level (13.2 - 13.4 V).  That's not enough for bulk charging, which requires 14.6 - 14.8 V.  Second, the length of the wire run back to the trailer can reduce voltage, depending on wire gauge.

So you might want to check your voltage after starting your engine and letting it run long enough that the internal cab voltage meter returns to it's normal position.
 
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