Dometic A/C glitch

[beaubeau]

Hi!

I have a 2013 Passport with a Dometic rooftop ducted A/C and Dometic single zone LCD thermostat.

Yesterday it was working fine.

At night, we like to leave the thermostat fan setting on Lo (not Au) so that it runs continuously through the night, for the white noise.

Last night, in this configuration, the fan turned off. I can cycle through Au, to Hi, back to Lo and the fan will come on, but still will turn off after a while.

Also, separately, I think ... I had the temperature set at 68 but the air temperature is 70. Nothing is running. So I lowered the temperature to 64, still nothing is running.

If I cycle through Furnace, Off, Fan -- the fan turns back on.

If I cycle on to Cool, the A/C compressor turns on, and the fan does too.

What could this be? I'm moving a few hours down the road today -- if this could be a thermostat problem, I could probably find one along the way.

Thanks for any help.

[MR_MAC]

Had a problem with my 2014 unit, short cycling, called dealer, girl at service desk said (she sounded like she knew what she was talking about) had a notice from Domitec to only run blower on auto. I did that , it ran ok for a while. then while down in Tenn. in Aug. it short cycled. We were hot. At home took to dealer, then ran the AC or a Wk. end with no problem. Took MH home, next day it short cycled again. I started by checking all the connections found the freeze senser on coil was not tight. Every thing was fine three mo. in Fla. The daaler tried to charge me for checking the unit. My wife took care of that quickly. This units blower stops when near temp. set, for a few seconds then restarts at low speed, the compreser keeps going on the recycling blower.

[beaubeau]

It's been a long time, so I don't remember the details, but ... I just checked all the connections at the A/C unit itself and everything started working - I'm assuming I just had a loose connection.

[CarterKraft]

Any update on any of these issues. I am having similar issue.

[Hiking_Hunter]

Learjet wrote:


... with the temp set low the whole unit turns off and it get hot. Then you must cycle thermostat off then back on. At somepoint it will do the same thing on low...no issues on high.

That sounds more like my symptom where the whole unit turns off and won't recycle back on until you "power cycle" the thermostat. Except I don't know about it not happening on HI fan. I run mine on AUTO which makes it downspeed to the LO fan before cutting off when the thermostat gets satisfied.

Doug - if beaubeau's motor is over heating, then why can he reset it by turning the AC off, then back on? Maybe because there has been some time lapse in that sequence for it to cool? It would be interesting for him to try "power cycling" it immediately to see if it will come back on...

[Learjet]

beaubeau wrote:
Hi!



Last night, in this configuration, the fan turned off. I can cycle through Au, to Hi, back to Lo and the fan will come on, but still will turn off after a while.

Also, separately, I think ... I had the temperature set at 68 but the air temperature is 70. Nothing is running. So I lowered the temperature to 64, still nothing is running.

.

Not what I read, and on my unit at night on low fan in the bed room with the temp set low the whole unit turns off and it get hot. Then you must cycle thermostat off then back on. At somepoint it will do the same thing on low...no issues on high.

[beaubeau]

Right Doug, you understand the problem correctly.
Thanks for the clarification.

[dougrainer]

Learjet wrote:

dougrainer wrote:
I would suspect a BAD lo speed on the fan motor(overheating the windings). But, it is easy to replace the tstat. I doubt the upper board is at fault. I doubt a reset will fix this type problem. Resets for operation problems rarely do on Dometic CCC systems. A quick test is to swap the Lo and HI fan speed wires and see if the fan fails when putting it to HI Fan(which will energize the LO speed wiring on the motor). If it fails on LO Fan(indicating the motor will not run on hi fan continuously), then you look at the upper board or the tstat. Doug

So, if the fan motor is overheating on low, why woulc the compressor turn off at the same time?

I did not get that from his post. What I understood was the LO Fan FAILED to stay running regardless of the compressor. He wants the fan to stay ON 24/7 which it should when set to LO instead of AUTO. IF the fan fails, the compressor WILL be killed by the overload on the Compressor. But, it will take awhile for it to overheat. Doug

[Learjet]

dougrainer wrote:
I would suspect a BAD lo speed on the fan motor(overheating the windings). But, it is easy to replace the tstat. I doubt the upper board is at fault. I doubt a reset will fix this type problem. Resets for operation problems rarely do on Dometic CCC systems. A quick test is to swap the Lo and HI fan speed wires and see if the fan fails when putting it to HI Fan(which will energize the LO speed wiring on the motor). If it fails on LO Fan(indicating the motor will not run on hi fan continuously), then you look at the upper board or the tstat. Doug

So, if the fan motor is overheating on low, why woulc the compressor turn off at the same time?

[beaubeau]

All good stuff, thanks! The thermostat is cheap enough and easy to just go ahead and replace when I get home. And I like the idea of swapping the Hi/Lo wires for while I'm on the current trip, at least for a diagnostic.

Thanks everyone!

[dougrainer]

I would suspect a BAD lo speed on the fan motor(overheating the windings). But, it is easy to replace the tstat. I doubt the upper board is at fault. I doubt a reset will fix this type problem. Resets for operation problems rarely do on Dometic CCC systems. A quick test is to swap the Lo and HI fan speed wires and see if the fan fails when putting it to HI Fan(which will energize the LO speed wiring on the motor). If it fails on LO Fan(indicating the motor will not run on hi fan continuously), then you look at the upper board or the tstat. Doug

[Learjet]

Hiking Hunter wrote:
Beaubeau -



Like I said, the repair tech thinks it is a bad thermostat, BUT - I don't know if he is aware of the reset that Chris Bryant described. The tech never mentioned that and I don't think he tried it. So, when you try Chris' suggestion, please post the results here - I may need to get this info back to my tech.

Thanx

I tried the reset before....no change...I think it is a software issue in the T-stat or AC control board.

[Hiking_Hunter]

Beaubeau -

My camper is in the shop right now for a very similar problem. The tech has diagnosed the problem as a bad thermostat and it is waiting for a replacement from Dometic.

My symptoms are: the AC (comp and fan) will run until the setpoint of the thermostat is satisfied and then cycles off. But it will never cycle back on even though the temp in the camper goes higher. I usually run it in AU mode and the step-down through the LO fan speed happens as it should at +4 degrees. I think if I have it in the LO mode, only the compressor is affected. The only way I can get mine to cycle back on is to turn the thermostat to the OFF setting, wait a few seconds, then turn it back on to any one of the AC settings (LO, HI or AU).

Like I said, the repair tech thinks it is a bad thermostat, BUT - I don't know if he is aware of the reset that Chris Bryant described. The tech never mentioned that and I don't think he tried it. So, when you try Chris' suggestion, please post the results here - I may need to get this info back to my tech.

Thanx

[Learjet]

I have the Dometic and single zone LCD t-stat also...I have experience the same thing with my Bedroom AC fan on Low over night, running fan on HI I've had no issues.

I don't know if the freeze sensor shuts it off or what, but on high it doesn't experience this issues...Dometic needs to improve this thermostat....it has other issues also, such as the fan switching from hi to lo and back to high as you initially cool the RV in Auto mode...this can also be fixed by using HI until the temp set point is reached.

[newman_fulltime]

sounds like the unit froze up and you need to do what Chris suggest.Also don't run the unit on low fan