When running in cooling mode on warmer days, the rear unit appears to switch into heat pump mode, blowing hot air. Turn off and restart later it cools for a while and then into heat pump mode again. Year before last, it did this on hot days a couple of times. Last year also a couple of times. Now although days are not "hot" yet, low 80's, it happens daily. Unit is 14 / 15 yrs old. Has anyone experienced this problem? If so, how did you remedy? Thanks for your replies.
Bill,
It sounds like the solenoid that does the switching between A/C and heat is getting either hot or weak and cycling off. IIRC on those units the swap valve defaults to heat if you have a coil failure. The coil can be replace with ease and is available off the net or a local A/C supply store.
Mike
Dometic | 3310714005 | Penguin Reversing Valve Solenoid Coil Harness | eBay (https://www.ebay.com/itm/Dometic-3310714005-Penguin-Reversing-Valve-Solenoid-Coil-Harness-/182431834431)
Agree with Mike, have had to replace 2. Check numbers on coil, this may be the one.
Thanks Mike & Jim for your help. I'll replace the solenoid and let you know if that fixes.
BTW, our experience is that only roof AC units cool and several other device can cool, so it may be better to not add complexity to a roof unit when we will not use it for heating. So we do not have heat pumps, just compressor coolers. Also heat from above does not reach the floor as well as a floor space heater.
I don't agree. We've had heat strips in both our previous coaches and used them a lot up north to "take the chill off". They actually do a good job before the big furnace gets up to speed. Down here, not worth the extra expense. We don't have heat strips on the current Carriers, but, hey, it's a "Texas Coach"!
Are the heat strips controlled by the thermostat?
If the solenoid does not fix the issue Bill you can try unplugging the phone cable connectors that attatch the gray cable to the black cables coming down from the ac. Sometimes they get some corrosion and then the thermostat gets confused. At least that is what I found was happening on our front ac.
Interesting about heat strips. We just removed our heat strips to give us better access to cleaning the evaporator surface from inside the coach. They came out real easy.
Over 17 years we never turned heat strips on, partly from louder sound than a small space heater, and heat on head instead of heat on feet.
But the real reason is we figured that 'saving' the roof unit for cooling would extend their life. And since we only had heat strips the 'wear' would just be the blower motor. The addition of heat-pump's high-pressure switching valve and louder compressor running to heat an RV feels less efficient than other choices.
I could see the convenience of heat pumps especially since they turn on and off from central thermostat. Also some do not like floor plug in space heaters. And since so many Foretravels have heat pumps, assume they are used for heat a lot.
We are not in very cold weather, so our propane furnace run is short on a cold morning. Also we are often plugged into shore power, so it makes sense for us to run small space heaters over extended hours.
When we change our roof air conditioners, we would not choose a heat pump model, even if less expensive. Air conditioners and refrigerators often have long lives because the refrigerant is completely sealed. Adding a movable valve to a sealed system can be a new weak point.
I removed the roof ac cover and located the reversing valve. Removed and replaced the coil to inspect and inspected all connections. Unit has worked fine since. I have ordered a new coil to have on hand. Thanks Mike and Jim for you advice and link for coil. And thanks Ron, I did not check that connection but will do so.