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Topic: Dometic heat pump, sometimes cycles to pump out HEAT when on COOL mode (Read 762 times) previous topic - next topic

Dometic heat pump, sometimes cycles to pump out HEAT when on COOL mode

Hello,
    My issue is in the title, "Dometic heat pump, sometimes cycles to pump out HEAT when in COOL mode. When the A/C is running and it goes to fan (I just keep it on high fan, not AUTO) after the cool temperature is reached and the compressor shuts off, in a few minutes I will sense a lot of heat coming out. I will then turn off the unit, turn it back on and within the 2 minutes the compressor will kick on and put out cool air. I'm not sure the compressor is running (next time I will be looking for that) when the heat is coming out but I suspect the compressor is running in the heat mode. According to the service manual it could be the thermostat, related wiring, or the reversing valve. On reading about the reversing valve I suspect it may be an intermittent solenoid as the energized mode is COOL.
 "DuoTherm roof top heat pumps have the solenoid energized in the cool mode. "
This leads me to assume that the default (non energized) mode is heat mode.
The intermittent solenoid could be the solenoid itself or the control wiring. I will be pulling the wires tomorrow to see if there is any contact issue etc. It happens so rarely that I was not concerned about it but with the FL heat now setting in I am afraid to leave the A/C on when we leave the rig for the day. Not sure what would happen with a runaway heat pump.

Any other ideas or has anyone experienced this condition?
Thank you,

Service manual PDF
http://www.dometic.com/QBank/EPiServer/Dometic/US/Manuals/Marine-manuals/Refrigeration/roof-top-ac-hp-diagnostic-service-manual_17589.pdf
Rick

Re: Dometic heat pump, sometimes cycles to pump out HEAT when on COOL mode

Reply #1 –
Yes, had the same problem, checked voltage to reversing solenoid when in cool mode and found
good, but when trying to pull coil off solenoid valve, found no resistance, meaning coil was not
opening valve. Found coil on ebay for $30, replaced coil and was good to go.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: Dometic heat pump, sometimes cycles to pump out HEAT when on COOL mode

Reply #2 –
Experienced the same problem last September.  Found the coil to be the problem.  With AC running it would get hot and the heat would kick in, once the coil cooled down AC would come back.
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: Dometic heat pump, sometimes cycles to pump out HEAT when on COOL mode

Reply #3 –
Quote from: jcus –
Yes, had the same problem, checked voltage to reversing solenoid when in cool mode and found
good, but when trying to pull coil off solenoid valve, found no resistance, meaning coil was not
opening valve. Found coil on ebay for $30, replaced coil and was good to go.
Thank you, do you have the link or part number for the coil?
Rick
 

Re: Dometic heat pump, sometimes cycles to pump out HEAT when on COOL mode

Reply #7 –
Here I've added the service manuals as a direct PDF attachment instead of links in case they disappear.
Rick