Can't find the breaker/fuse for my air conditioner

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Frizzylizzy

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May 3, 2018
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Last year I purchased a 34' 1993 Carri-Lite 5th wheel trailer. I used the ac a couple of times and all was fine. I went to turn it on last week and nothing happened. I'm assuming the issue is breaker or fuse related. The only fuses I find are 12 volt and the breaker is the main one. Also, the unit is controlled by a wall thermostat, which I'm assuming is a replacement from the original roof controls. Anyone have experience with this? (I apologize in advance for perhaps sounding a bit ignorant - I'm a middle aged woman pretty much on my own)
 
Humm..  Well since this is an A/C I need a bit more info, 30 or 50 amp RV, one or two A/C's  But I'll go ahead and answer anyway

The A/C uses two power sources and BOTH must be present for it to work

For 120 volts.. On a trailer you do not normally have a generator so the A/C breaker will be in the same box and the MAIN circuit breaker, you will also find the breaker for the TV's and Microwave and other stuff there... DO NOT TRUST YOUR EYES touch the breaker and the one that FEELS different is the bad guy, TUrn off hard and turn back on.


It also uses 12 volts via the thermostat for control.. that will be on the fuse panel.  Use a test light to test every fuse.

Finally the T-Stat may have failed... Some contain a dry cell (AA usually) battery.

And then there is the ever popular "Other issue"

I hang in Mid-Eastern MI  Davison and St. Clair areas.  if you are near I can grab a test tool or 3.
 
John steered you in the right direction. I have seen the house battery low cause this problem the majority of the time. See if your battery is charged. If your fridge runs on 12volt see if it turns on if you don't have a tester for battery. If so then look for breaker as John mentioned.
 
The wall thermostat was likely factory-standard on a Carrilite. Few mid-high end RVs use a/c units with the controls on the ceiling unit itself. Are there any controls visible on that unit?  The thermostat requires 12v power and sends the "cooling needed" signal to the a/c control board as a +12v signal, so you can't turn on the a/c unless the thermostat is powered and working.

Somewhere in the RV will be a panel with at least a few circuit breakers, one of which will be for the roof a/c unit. RV makers are endlessly creative about stashing them away, though. You imply you found the main breaker (whether 30A or 50A)? Usually the branch circuit breakers are in the same place.

Do other 120v items work, e.g. wall outlets, the fridge in AC mode, etc? In other words, is the a/c unit the only 120vac-powered item that doesn't work?  Check them all to see.

 
Thank you everyone for the info. I live in the trailer and everything else works fine. I will get a fuse tester and hope that is the culprit. It seems the most likely. The breaker that I found is marked 'main' and is 40A. The breaker next to it is marked 'blank'. Thanks again. I'll update as I discover things. Oh, and I'm in central California.
 
Well, it looks like all the fuses are fine. My thermostat is a Coleman. I've got pictures, but they're too large for an attachment and I haven't figured out how to get them small enough. I'll post them when I do.
 
Frizzylizzy said:
I've got pictures, but they're too large for an attachment and I haven't figured out how to get them small enough. I'll post them when I do.
Click to expand...

If your phone or camera has an Email option, that will usually reduce the picture to the proper size to post here.

Or if you have Windows Paint, you can Open the picture into it, click Resize on the Home menu and select the size you want.  Usually 640x320 or so pixels is good.

Then click "Save as", change the filename so it doesn't overwrite the original, and save it as a .jpg
 
Okay, I found the breaker panel, finally! Unfortunately, the breaker was not tripped and is not the simple fix I was hoping for. I'm assuming that it must be the thermostat. Nothing happens when the thermostat lever is moved back and forth(except the click from the prongs when you go past the current room temperature). I would think that at least the fan would turn on. Is this an acceptable assumption? And if it is, is it possible to replace the old, now unavailable thermostat with a newer one? It only controls one ceiling mounted air conditioner unit. The heater has a separate (and updated-digital) thermostat. The a/c is a Coleman 7000 series. The thermostat is #6799B6951.
I seriously appreciate any and all help.
 
Very occasionally a breaker can trip but not appear tripped. I would turn the AC off, then flip the breaker off then back on, then try the AC again. Very small chance it could work but free to try
 
Check your 12 volt fuses - the thermostat and the interface panel inside the A/C that replaces the manual controls require 12 volts to operate.

It may be on the same fuse as the furnace.
 
Also check the furnace. Atwood Hydro-flame provides 12 volt to the T-Stat and has a circuit breaker on top of the blower housing OUTSIDE the RV. you need to remove 4 screws and remove the outside access plate to see the breaker, it looks like a common rocker switch.
 
There is a time delay built-in to the ACs, so if you turn on the AC and then immediately move the thermostat to require cooling, there will be a delay before things start working. Did you wait a minute or two for the AC to come on?
 
Sun2Retire said:
Very occasionally a breaker can trip but not appear tripped. I would turn the AC off, then flip the breaker off then back on, then try the AC again. Very small chance it could work but free to try
Click to expand...
I did try this, with fingers crossed. Unfortunately it did not work. Thanks anyway.
 
Lou Schneider said:
Check your 12 volt fuses - the thermostat and the interface panel inside the A/C that replaces the manual controls require 12 volts to operate.

It may be on the same fuse as the furnace.
Click to expand...
I have checked all the fuses. 3 times....
 
BruceinFL said:
There is a time delay built-in to the ACs, so if you turn on the AC and then immediately move the thermostat to require cooling, there will be a delay before things start working. Did you wait a minute or two for the AC to come on?
Click to expand...
I actually waited quite a while, a few different times.
 
John From Detroit said:
Also check the furnace. Atwood Hydro-flame provides 12 volt to the T-Stat and has a circuit breaker on top of the blower housing OUTSIDE the RV. you need to remove 4 screws and remove the outside access plate to see the breaker, it looks like a common rocker switch.
Click to expand...
The heater has its own thermostat and it works fine.
 
We?re you able to check your thermostat to see if it has a battery, as John From Detroit mentioned?  That sounds like the last cheap, easy thing that might fix it.
 
Here's an update to my thermostat issue. I finally got someone to look at it. He found that the 12volt wire was not supplying power to it. We don't know why. Thankfully, the heater thermostat is right next to it and he was able to take its 12 volt wire and hook it up to a new thermostat to run the air conditioner.
Thank for everyone's attempt to help.
 
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