A/C or Thermostat Problems

We have had issues with the A/C unit or the thermostat.  When cooling, the unit would never stop when it reaches setpoint.  It also short cycles when changing from hi to lo speed.  Dometic suggested resetting the thermostat, which we did.  Now it stops when it cools to setpoint but continuously short cycles when switching from hi to lo speed.

Since we are the second owners, the 2-year warranty on a 2016 A/C unit does not apply.  I was wondering if other have had this problem and know what was done to correct it.  Dometic thinks its a control board, thermostat, or both.

Thanks.

Whenever ours acts up, usually it's only running a single cycle and not turning back on well below the set point, we pull the passenger side fuse cutting power to the thermostat for about a minute to reboot.

the suburban tech i talked to said the "short cycle" is normal when shifting from hi to lo speed on the fan.

We have had issues with the A/C unit or the thermostat.  When cooling, the unit would never stop when it reaches setpoint.  It also short cycles when changing from hi to lo speed.  Dometic suggested resetting the thermostat, which we did.  Now it stops when it cools to setpoint but continuously short cycles when switching from hi to lo speed.

Since we are the second owners, the 2-year warranty on a 2016 A/C unit does not apply.  I was wondering if other have had this problem and know what was done to correct it.  Dometic thinks its a control board, thermostat, or both.

Thanks.

That is normal.  Whenever the fan changes speed, the fan will shut off, wait a few seconds, then come back on at the new speed.

The compressor will stay on during thr fan off/on cycle.

In auto fan mode, the fan will go HI whenever the interior temp is 5 or more degrees (F) warmer than the setpoint. And then drop back to LO when the room temp is less than 5 degrees from setpoint. 

Also, if the A/C detects ice on the evaporator coils, it willshut off the compressor, jump the fan to HI and run until it senses no more ice on the coils, it will then turn the compressor back on.  You can tell when it's in "unfreeze" mode when the air coming out of the A/C is not cool.  This happens a fair amount when it's high humidity outside (or inside).

Anyway all that is normal.

We picked up our 2910T end of Jul last year... Don't have that many miles but will ret to PC next week for an appt to see why AC not doing its thing. Was front AC now we have odd problem with rear AC.  They have different thermostats... One very complicated and needs a lot of programming other is usual simple one. Front AC  would come on go off then right back on again... Not our first AC or RV and sure seemed odd. rear one now not cooling. Have a short list more than AC... But such is life... When we are out now that Mr has done a couple of big jobs it does well... Size wise it works.. Dog has not complained.
I think Mr would go to Elkhart for not much reason to stop at Martins for their fried chicken. He swears by their presentation. I may have to freeze some before we head back home.

When ours short cycles, it cycles off-on-off-on about 3-5 times.  I've been on the phone with Dometic, I've learned to keep calling with the same question until you get someone who can actually help....

During last useful call they told me that as long as the compressor remains running this is normal.  Not sure I buy it, but if that is the case we plan to live with it - we will just lock the fan on HI speed.

The RV is about an hour from our house so testing is a time consuming affair.

Henry3 - your front AC problem sounds like what our was doing too.  Dometic can walk you through the thermost reset procedure which fixed that issue with ours.  I'd share but but my notes are in the camper.  Two units are the way to go on a 2910, one does not cut it on a hot day in the sun....

Thanks for all the input.

Hi All,

It does seem that many issues with roof-top a/c units are related to the smart digital thermostat.  People with the mechanical one as shown here, seem to have fewer issues to report.

As for Irene and me, we like the simplicity of our mechanical one.  I've adjusted it many times during the night in the dark with eyes closed while staying in bed under the covers.  We have a digital one at home and are always frustrated making changes to it.  The next time I paint the hallway, I am patching the mounting screw holes and installing the old round Honeywell back in.

I have concluded that I am an old fart. 

Ron Dittmer

With at least models from 2014 on up until now, the on/off if the FAN is perfectly NORMAL.  The compressor will stay ON.

OR

If the evaporator (cooling) coils start to ice up, the compressor will shut off and the fan will cycle on/off until the unit thinks the ice is gone.  This is all NORMAL.

It has nothing to do with the thermostat, it's in the design of the a/c unit itself and is intended to reduce wear.

One other thing, make sure you keep the air intake filters clean!  I check, and usually clean, mine about once a week.  It does make a difference.