Duo therm ac heat pump blowing hot air

[efstewart]

My 2006 DSDP model 3817 rear ac/heat pump has recently started blowing hot air. It starts and runs cold for about 10 minutes and then it starts to get warm. When this happens the unit gets a little noisy like it is trying to work hard, but it keeps going.

My front unit is fine, and since this problem has started I just run the front and turn off the rear. The front unit is strong enough to give some cold air out through the rear ducts. I inspected the rear unit on top of the motorhome and did not see any obvious problem.

I am mechanically inclined and do most repairs myself, but I don't have any experience with ac units or heat pumps. Anyone know what could be wrong? A RV parts house nearby (Southern California) said that the whole unit may have to be replaced.

[hometool]

that sounds to me like lack of cooling air flow through the condencer coil (the outside fin thingy) can get pluged with bug debre or just dirt and dust

[siggyd]

If the unit is set to Cool and then after a few minutes or less starts blowing
real HOT air, I would say the solenoid coil over the reversing valve is opening up or is loosing the 120 volt AC.
Had the same problem on my former 05 KSDP, the coil was opening up
after ~ 30 seconds.Replaced the coil and all was good.
Siggy

[efstewart]

To siggyd, after reading part of the service manual that is posted under the tips and mods section, I think you might be right. Any idea how much it costs and is the installation difficult?

[siggyd]

The coil is very easy to replace,take off 1 screw that holds the coil,slide the
coil off the reversing valve. put the new coil on. The 2 wires for the coil you can just cut and splice,or some of the coils may have connectors.
I think,I paid about 35~40 for the coil from COLAW rv parts & salvage,877-548-2125.
The coil was made for only 110 volts +/- 10% in China,
No wonder it fails.
Siggy

[efstewart]

So, I replaced the solenoid coil, and turned on the air. It started blowing warm air again. Everything works fine except it will not blow cold air like the front unit does. Do I need a whole new heat pump/AC? Or is there something else I can try?

[Air Baron]

My front Duo-Therm was blowing hot air, even though the controller had both units in A/C mode. I paid a mobile tech $120 to determine it was running in heat pump mode. He climbed on the roof, took the cover off, pulled the plug off the reversing valve and cleaned the connection...both with a pencil brush and spray cleaner. Plugged it in, turned it on and it has been working fine for 2 years now.

[efstewart]

Air Baron, I will try that and get back to you. I did not know there was a separate plug just for the heat pump. So I will look for one and give it a try!

[94-Newmar]

Heat pumps are always in heat pump mode UNTIL the reversing valve solenoid is activated - the solenoid stays energized the entire time it's cooling. Make sure you have a good 115-120 volts AC at the reversing valve solenoid when you set the thermostat to call for cooling.

[mel s]

[QUOTE=efstewart;2131871]So, I replaced the solenoid coil, and turned on the air. It started blowing warm air again.[/QUOTE
Your Duo therm ac heat pump is blowing hot air?
Isn't a heat pump supposed to blow warm/hot air?
Mel
'96 Safari, no heat pump

[efstewart]

To Mel S, yes the Dometic Duo-therm A/C heat pump, is supposed to blow warm air when you set it to heat pump, however, I had it set to A/C mode and it should then be blowing cold air. I also noticed that the compressor appears to be working, because some lines are ice cold and some are warm. I guess they are the inlet and outlet freon lines.

I also unplugged the reversing valve wires to check for corrosion, but they looked brand new. Any more ideas before I take it in and pay possibly lots of money?

[ga traveler]

Probably the reversing valve is going to have to be replaced. We had to replace several of these in this time frame. Our shop did not do it. We had a AC man come in and do it.