Coleman Mach10 AC/Heat Pump switches to HEAT on its own

[rayk4e]

I could use the advice of an expert, or someone who has had the same issue.

I have the Coleman Mach10 15k BTU AC/Heat Pump units (x2). On a few occasions (like today) one of the units, this time and most frequently the rear one, will switch from AC to Heat Pump on its own without any intervention on our part. My wife is a travel nurse who works overnights here in Tucson, and she will be sleeping comfortably with the bedroom AC on at 72 degrees, and an hour later it's 88+ degrees. I have to turn the unit off, then wait about 5 minutes for it to shut down completely and rest a couple of minutes, then turn it back on before its in the AC cooling mode again. Any thoughts?

I have read posts about a reversing valve as a possible culprit. Is there an easy diagnosis of this valve, or something I can do as preventive maintenance? We don't have the luxury of having our motorhome at a repair facility for days.

Thanks in advance for any advice, be it from an expert or someone who has had a similar problem.

[vito.a]

You're correct. The reversing valves are malfunctioning. On a Dometic Duo Therm heat pump the reversing valve coil is replaceable. Hopefully Coleman has the same part available.

How old are your units?
I ask because this is usually the first sign they are aging out.

[DancinCampers]

Which tstat does your system use?