AC not working

[navybanker]

Checking the ac before a trip and living room unit will not come on. The thermostat is a Dometic single zone unit and has 12V power to it and all the lights on it work as they usually do going from fan to heat pump. Nothing works. The bedroom ac works okay. No indication of blown fuses or tripped breakers. Have reset the thermostat and nothing works. Have read all posts can find on net and read most manuals but have not found anything to do that will work. Have climbed on roof and removed the cover. The only thing noticed is a green wire attached to metal on the unit that is corroded where the wire is attached by a screw. Have sprayed penetrating oil but unable to get the screw out in the close quarters to clean. Could this be a ground wire? Think this should only affect the ac/heat pump but not the furnace. Too hot to attempt the furnace or heat pump. And, too hot to stay on roof very long! Thanks,

[DQDick]

If you've flipped the breaker to make sure it's not tripped, I'd check the back of the breaker box to make sure the wires are tight. One other thought, have you checked other lights and appliances to make sure you haven't lost one leg on your incomming power. Also check those two breakers.

[navybanker]

I checked the wires to the breaker and appear to be tight. Not a lot of wire to pull out very far! Other appliances on the leg are working. Thanks,

[DQDick]

Sounds like it's time to call Dometic and get their thoughts.

[mlh]

Something to remember Green is the universal ground.
Lynwood

[navybanker]

Going to contact Dometic but want my "ducks in a row" before then. Dealer thinks it is probably the thermostat based on their experience. The green wire appears to be green but somewhat faded and dirty. Don't know of a reason to have a wire attached directly to metal other than for a ground. Assume there is a fuse for the thermostat since it is 12V but if there is where is it? Yes, have 12 V to the thermostat according to multimeter but just wondering. No red lights below the fuses indicating a blown fuse on the panel. So back up on the roof tomorrow and try to remove screw on "green" wire.
I just want to fix without hauling it 50 miles and possibility of two trips and two days being 200 miles. Thanks,

[Rondo]

Bobby-- Is the wire that is corroded attached at the a/c unit or is it corroded where the wire is grounded to another piece of metal on the framework or something else on the unit. If the wire is coming out of the unit and connected/corroded at a screw attached somewhere on a frame or whatever and you can't get that screw out just cut the wire next to the screw and prep it for another connection and connect it to another screw if there is enough wire to do so. If not, use a wire splicer and add an additional length of wire so you can connect it with another screw into that metal. If it is copper wire and connected to an aluminum piece of metal this could cause the corrosion also thus not making a good contact and not grounding the unit properly. Keep us informed on the problem and if you get it solved. If you can't get it solved, call Dometic and see what they have to say. They have a good customer service department and can diagnose over the phone most of the time.

[ChuckS]

I’d be checking the junction box from thermostat to AC unit. Try reseating comm cable at junction box

[navybanker]

Back on the roof in the cool of the morning such as it is. Got the screw fastening the green/yellow AWG 16 wire out. Cleaned the connector and sprayed battery terminal cleaner on it. It is connected to "metal", not aluminum inside the unit. The wire is then bundled with other wires and inside a rubber tube going under the black plastic cover under the top hard plastic cover. Does that tell you how much I know about electricity! Fan and AC will still not come on. Furnace works since it was cool enough for it to light and heat. I see the "comm" wire going to the thermostat but assume the "junction box" is inside the area behind the pass through storage.

Unfortunately or fortunately, DW was home and saw me on the roof! Her comments were stop and take it to the dealer before you break your neck or electrocute yourself . Will talk with Dometic Monday to say what they say. Dealer said they will work me in before the trip. That shouldn't be too dangerous! Thanks,

[TnT]

Having the same problem on my 2016 3820fk. I too would have the 50 mile one way trip to rv dealer and if they could work me in. I call Dometic they told me they didn’t to much diagnosing over the phone had me reset thermostat. That didn’t work so they said I need to get a tech to work on it. I’ve done everything navybanker has done to the same results

So I have a friend who works for an rv dealership in Eugene Oregon. I contacted him, He talked to his service department they are thinking maybe the mother board up on the roof so I ordered 1. I also have him discussing with the techs whether it could be the start capacitor. I do have a mobile rv person in my area. As soon as I hear back Monday on the capacitors(there are 2) if I need to order one or both I will and when I get the parts I will call the mobile rv person to install. Will keep you informed with what I find out and the out come.

[Slow Hand]

I don't know what year ypour rv is but my 03 has some wire connections inside my unit under the cover for the ac inside. I have taken my cover off and unplugged the connector and plugged it back in and it all worked.

[Batt chief]

Two things you might want to check 1) circuit board there is a 3 amp fuse on circuit board that controls thermostat lead to board 2) disconnect wire on thermostat and tap relay on circuit boards if they get hot enough will stick together just like points on the old cars. Then reconnect AC wire back to thermostat you should here clicking letting you know relay is working again. Just had it on mine now fixed until next time then will replace circuit board.

[StageCoachDriver]

Yes, green is ground. White is neutral and red or black is hot.

[zwma6@aol.com]

I have a quik fix that might work well ! Go to the thermost and press TOP and BOTTOM buttons and hold them in...........at same time switch on/off once. OMG ! thats a reset trick a repair guy taught me.......woooohoooo Another great idea. I bought a 5000BTU tiny window unit at WALMART. It works like a FREEZER w/a big fan on it. It is sooo quiet it's crazy. I m in 38 foot 5th wheel and I can't hear it in my bedroom .. BEST 147buck$ I ever spent.......that included tax lol
I don't use the DOMETEC very much and monkey-ass HOTT down here in FLA......babe

[navybanker]

I have done the reset and the initialization afterwards and did not work. Again, the furnace works so the thermostat is at least working for that. Thermostat is getting 12 volts. There is something loose/rusted, a non functioning capacitor, or something not communicating with the unit on top. The fan is not coming on. Thanks for your input!

[Bridge4d]

My experience with capacitors is from pool pumps and home AC units, not these RV AC units...but I image the they'd make the same noise if it was a bad capacitor. If you're up on the roof and get someone to turn the unit on at the thermostat I would think you'd hear the relay kick over and then a humming sound. I don't know how accessible the capacitor is on our rooftop ACs (yet, but I'm sure my time is going to come) but that's easy enough to test with a multimeter. You should also be able to test the lines at the compressor and see if you're getting current there.

Also, if there's a chance it's a bad Thermostat you might try swapping in your bedroom thermostat (which you know works) and see if that kicks everything on.

[Mikeb]

just had the same issue with my ac. bypassed circuit board. the fan and compressor worked fine. bought new circuit board from local dealer. installed and all works great now.
local dealers couldn't get me in till August 1. I wasn't gonna wait and cancel trips. contacted Dometic support and they sent me a reimbursement form(pending their approval)

$95.90 shipping included

2018 Montana HC 345rl

[navybanker]

Taking it in the 29th. Too hot up there! We have a five week trip planned starting August 14th and want everything checked out. Will let you know what the dealer says. Thanks,

[mlh]

If it was my camper and I had tried everything I could and still couldn’t get it to work and wonted to use my camper I’d replace the AC. They are fairly easy to replace. The hardest part is getting one up on the roof but that isn’t that bad. Set a ladder up beside your camper shove it up. You can put a rope around it with someone on the roof to help.
Lynwood

[mazboy]

you know, it could be anything. my issue was the 'module' that connects the 'telephone' type wire was corroded. for a quick $285 it was cured.


probably get it to an expert who deal in this type of a/c