RV roof A/C trouble shooting:

[speeder]

Ok, guys, I took the cover off of the unit that doesn’t run and I’m looking at the capacitors(?), which do not show any visible signs of failure like being swollen, etc.

Can anyone tell me where to check for power to the unit? Here are some photos I just took:

[speeder]

Looks like there is no power at the switch inside of RV. The breakers are all in the “on” position and I’m not seeing a fuse anywhere on the unit. Not sure where to look now.

[javadog]

Take out the supply air grille assembly and look up inside. You’ll see the power wiring to what passes for a circuit board, which really is just old mechanical relays and the like.

[speeder]

Originally Posted by javadog

Take out the supply air grille assembly and look up inside. You’ll see the power wiring to what passes for a circuit board, which really is just old mechanical relays and the like.

Do you mean the cover inside of the coach? I did remove it and all I saw were a couple of switches that the knobs attach to, nothing that looked like a circuit board. I can get some photos of that tomorrow.

[fintstone]

Look in here for a control box (in front of the evaporator). It should have a thermostat with a sensor that goes into the evaporator.

[javadog]

Yes. Look up into the area Fint is pointing out, but from the inside of the coach. Or, pull off the sheet metal on the roof. Either way, it’s in there somewhere.

[speeder]

Ok, and what should I be looking for when I find it? Remember, I'm getting nada power too the switch. Thanks again.

[javadog]

There will be power coming from the RV to the A/C unit. Test that first. If you have power getting to the unit from the RV, check to see if the control board is calling for cooling, for the fan to run, etc. according to what the thermostat is set to do.

Lots of videos on YouTube showing how to do all that, if you’re not familiar with A/C units in general.

[javadog]

Look for the data plate that tells you what model A/C unit you have.

Find the wiring diagram, it will look something like this:







There is probably a nine pin connector that plugs into what passes for a circuit board in these things, where you can test the functions you need to test.

[fintstone]

You should have a panel with circuit breakers and fuses. This uses 120V (gen or shore) to run the roof system and 12v (vehicle battery) to control it. Are you sure you have both 120AC and 12VDC at the terminal bock from the breaker and fuse respectively?

[fintstone]

Originally Posted by speeder

Ok, and what should I be looking for when I find it? Remember, I'm getting nada power too the switch. Thanks again.

If you have checked input power, this is where the control box typically is (you can check the AC and DC here where it comes into the system):



From this video which shows basic troubleshooting of the unit.
https://youtu.be/3VckFAXg1CY?feature=shared

[speeder]

Thanks! Here’s the view from inside with the cover off:

[fintstone]

Best bet is to measure at the relay that is probably better accessed from the top. You should definitely have one to run the compressor and probably another to run the fan. They would most likely be controlled by 12v in (to turn them off and on) and pass 115 AC. Do you have either 12v or 115 at either of the switches/wires inside?

Before that, I would look for the 12v fuse that provides power (if there is no power at the switches). It should be with the other fuses (fuse block) ...assuming your system is typical.

[javadog]

Originally Posted by speeder

Thanks! Here’s the view from inside with the cover off

Ahh, now you’re getting somewhere!

Break out the multimeter, consult the wiring diagram and start testing.

[red-beard]

The capacitors "look" OK, but they are rusted. "While you're in there" I'd go ahead and replace those after you solve the power issue.

[speeder]

Ok, back on this thing. I pulled it inside out of the heat and just came down from the roof. There is nothing behind the front of the sheet metal other than the big cord that runs from the temp control to the other unit maybe(?) It disappears under the aluminum body/roof going towards the front. I still have no idea what I’m supposed to be testing or looking for power:

[javadog]

I'm working on it.

Pictures are ****, trying to figure out what goes where.

Is that a piece of Romex I'm seeing in the first and third photos above? From where to where?

You ever find a wiring diagram label or model #/serial # label on the thing anywhere?

[javadog]

Capacitors:

1 compressor run
2 fan
3 compressor start




House wiring to the unit should be behind one of the selector switches on the grille assembly inside the unit. Open up behind them to look. Start with the one on the left, first.

[red-beard]

Why not upgrade to an inverter AC unit

https://www.amazon.com/dp/B089MYDLTY/

Less power, quieter

[speeder]

Originally Posted by red-beard

Why not upgrade to an inverter AC unit

https://www.amazon.com/dp/B089MYDLTY/

Less power, quieter

If the unit was completely shot and needed to be replaced, I'd definitely be looking at options and that one looks good. As it is, I have so many projects going that the RV is not a big priority and I just want to get what is on it working if possible. Still, I appreciate it, James.