Rear AC in 364 frozen and running with furnace

[Walte1fr]

Our rear AC ran for the first time today for most of the day. We got back to camp and the breaker was blown. I went up top and saw all of the lines were frozen. 4 hours later I flip the breaker on and the unit still tried to run while I had the thermostat set to furnace not AC.
Even if it's as easy as low refrigerant is that easy to add or is it what I'm reading that it's just time for new?
If it was low refrigerant or leak would warranty even cover that since they say they don't cover AC refrigerant.

[nicholsonv]

Assuming you might have a dometic AC. Put the thermostat on auto (AU) and the furnace will run by itself.

[Walte1fr]

Right. The furnace is running. But the air conditioner is also. It almost seems like it's just the evaporator fan. Not really blowing any cold air. Just running.

[A32Deuce]

Put thermostat in fan mode and select AU. Then select heat mode. Should just run heat.

[Herk7769]

If it is a humid day, constant running of the AC will not allow the coils to shed the frost into the drip pan.

INITIALLY

Set the AC temp to 10 degrees below outside air temp until the humidity is removed. The AC MUST shut off, warm up, and restart in order to remove the humidity.

THEN

When the air is dry, you can run it as cold as you want.

Not getting the air dry can even damage the air conditioner by circulating hot coolant back into the compressor. At that point you are praying that the thermal breaker in the compressor works or the "ice detection probe" (which is supposed to shut down the unit to save the compressor) has not fallen out of the coils.

[Walte1fr]

I'll try it again today but we got back and the breaker was tripped and it was froze. Hopefully if it is shot the extended warranty covers it

[Walte1fr]

Just flipped the breaker back on and even with the thermostat as "off" the air conditioner pump was running then it started blowing out cold air. Only way to shut it off is to trip the breaker. Any other ideas or just head back to the dealership?

[Herk7769]

Originally Posted by Walte1fr

Just flipped the breaker back on and even with the thermostat as "off" the air conditioner pump was running then it started blowing out cold air. Only way to shut it off is to trip the breaker. Any other ideas or just head back to the dealership?

That is a good sign.

Are you sure the thermostat that is "off" the one for the rear AC?

If you use the breaker to shut it off, DO NOT reopen it for 3-5 minutes.

Coolant returning to the compressor is flowing in the wrong direction and restarting the compressor can damage the unit.

Oh, BTW, these units are not designed to be serviced. They are sealed units with no fill port. A low coolant condition requires unit replacement as the process to purge, add a fill port, leak check, and re-service costs more than a new AC.

[Walte1fr]

Nope I don't reset the breaker and yes. I turn the thermostat off and it runs. I give it a minute or 2 and it keeps running then I give up and shut it off with the breaker since it sounds like the compressor is what is running and not the fan which seems opposite usually I thought the compressor shut off then the fan ran so that it could cool the Pump down for a minute.

[Herk7769]

Originally Posted by Walte1fr

Nope I don't reset the breaker and yes. I turn the thermostat off and it runs. I give it a minute or 2 and it keeps running then I give up and shut it off with the breaker since it sounds like the compressor is what is running and not the fan which seems opposite usually I thought the compressor shut off then the fan ran so that it could cool the Pump down for a minute.

When you kill power to the unit, the control panel also loses power, so everything dies at once.

[Walte1fr]

Yup but when the breaker is flipped back on and the thermostat is off it shouldn't kick on correct? That's the issue. Nothing on for the thermostat flip the breaker back on and the compressor runs.

[Herk7769]

Originally Posted by Walte1fr

Yup but when the breaker is flipped back on and the thermostat is off it shouldn't kick on correct? That's the issue. Nothing on for the thermostat flip the breaker back on and the compressor runs.

You are right; that should not happen.

Please don't take offense at some of these things I would look at. You are there; it is your camper; and I have no idea which thermostat you have or are looking at.

I would look at:

1) The thermostat. What is the model? Do you have the manual?

1a) Are you using the correct thermostat for the back bedroom AC?
1b) If it is a dual AC controller, is the correct AC selected and turned off?
1c) Thermostat bad?

2) The AC itself.

2a) There are start control relays on the control board. Maybe one of them is bad so the compressor always runs when power is applied?
2b) Bad thermal fuse on the blower motor?

I am pretty much shot here. After this it is multi-meters and wire trace.
If anyone has an idea what else to look at; have at it.

[Walte1fr]

Oh no offense at all I reach out for help because I'm new to this. I thought it was just not understood what the problem I was having. No problem at all. It should still be covered under extended warranty so I'll try some of your ideas then if it's not it then off to the dealer I'm thinking for warranty work

[VinceU]

Originally Posted by Walte1fr

Our rear AC ran for the first time today for most of the day. We got back to camp and the breaker was blown. I went up top and saw all of the lines were frozen. 4 hours later I flip the breaker on and the unit still tried to run while I had the thermostat set to furnace not AC.
Even if it's as easy as low refrigerant is that easy to add or is it what I'm reading that it's just time for new?
If it was low refrigerant or leak would warranty even cover that since they say they don't cover AC refrigerant.

For the last couple years most RV manufactures wire the thermostats to also run the vent fan in the ceiling when the heat is selected. This is to help circulate the heat as the std fan is becoming anemic. The compressor does not operate in this mode. Switching the fan control to auto should stop this operation. The next step is to correct the thermostat.
I've seen that thermostat on line with good instructions.

[Walte1fr]

Originally Posted by Herk7769

You are right; that should not happen.



Please don't take offense at some of these things I would look at. You are there; it is your camper; and I have no idea which thermostat you have or are looking at.



I would look at:



1) The thermostat. What is the model? Do you have the manual?



1a) Are you using the correct thermostat for the back bedroom AC?

1b) If it is a dual AC controller, is the correct AC selected and turned off?

1c) Thermostat bad?



2) The AC itself.



2a) There are start control relays on the control board. Maybe one of them is bad so the compressor always runs when power is applied?

2b) Bad thermal fuse on the blower motor?



I am pretty much shot here. After this it is multi-meters and wire trace.

If anyone has an idea what else to look at; have at it.

I just went out and ran it again.
Maybe 2A sounds dead on here is scenario
Thermostat off displaying nothing. Flipped the breaker on and the compressor on the AC part started but no blower fan.
So I would think to rule out 2B since the blower works when it calls for cold air (when I select an AC temp lower than room temp)

I looked and couldn't find the manual for the AC. I have them all except for that apparently. I have the build sheet and will include it. There are 2 sheets. One that says what was included one that shows the model.
1A: it is the one installed from manufacturer.
1B: there are actually 2 different thermostats. One for front AC/heat strip and furnace. A second one installed in the back to control the same setup in the back.
1C: it could be but I wonder why compressor would turn on and no blower if it was calling for AC behind the scenes.

[Walte1fr]

Here is the build sheet. It is AC #2 since AC #1 is a 15k unit which is installed in the front. The rear is 13.5.
Hope this helps I'm thinking it's a failed unit at this point

ok well I couldn't upload a picture. but I also can't read the hand writing on the sheet. It's Dometic and maybe a model number B5793x (x= uknown) or the 7 could also be a 2?
Dometic black 13.5k AC with a heat strip

[Herk7769]

My next step would be to remove the front thermostat (and carefully remember what color goes where - make a drawing!) and swap it with the back one.

Also draw a diagram of the rear one too.

If that fixes the rear AC, it was a bad thermostat.

[Walte1fr]

That's a good idea also. Would the compressor be ran from the thermostat though? The fan doesn't blow when it's not on. Only the compressor runs whenever there is power to it? I wish I had a wiring diagram for the unit or the actual part number since I can't read the handwriting on the build sheet hahah

[VinceU]

Go online to Dometic rooftop a/c installation and maintenance. They have schematics with and w/o heat .
No the compressor should not run without the fan and the entire system ready to go.

[Walte1fr]

Oh great. Thank you