Duo-Therm Bedroom A/C Not Cooling

[Hoss7]

We just arrived to a campground in Las Vegas where it's 112* F and the bedroom roof air unit is not cooling. It will cool for about 30 seconds, then you'll hear a blow-off/purge sound, then it blows hot. The compressor will kick on maybe 30-60 seconds later for another 10-30 seconds, then start blowing hot air again. We have never had a problem with this in the past, so I don't know if it's attributed to this heat. Last night, it cooled down to about 84* F outside, but it still didn't work. The other two front most A/C's are working fine.

I removed the interior filter and cleaned it thoroughly, and went up on the roof and removed the cover and blew out all the coils with compressed air, so everything is clean. Nothing stood out of the ordinary up top on the roof when I removed the cover.

The unit is a Duo-Therm 630516.321. Thanks for any insight!

[Jyrocharlie]

Wash out the rear coils with water. Don't get water on the motor. Make sure the fan blade turns free. Check for damaged fins on the rear coil, they make a "fin comb" to fix any damage to the fins. The fin combs are selected by measuring the fins per inch. Blowing out the coil folds the fins over and prevents air from getting through and removing the heat out of the compressed hot refrigerant gas.

[96 Wideglide]

Sounds like a fried start capacitor.

[kenwyatt]

If you can check both the start and run current with a clamp on if it will run long enough to get the second reading, could be the compressor or as mentioned a cap, the current readings should be written on a data tag near the compressor

[jacwjames]

If these are heat pump/AC units if the reversing valve is going bad it would start blowing hot air. This happen on one of my AC's, turned out to be the power wire going to the reversing valve contacted the metal tubing, melted the insulation and arched out.

[Ivylog]

What you are hearing is normal when the compressor stops running. Your unit defaults to heat when there is not 120V to the reversing valve releasing the pressure. Many of these problems are caused by poor connections on the phone type control cables. They plug into the control board up top and there are connections in the return air area so I would clean them on the middle and back unit.

[kenwyatt]

Did not know about the default to heat mode. Will have to remember that one

[Ivylog]

By 2010 Dometic changed the default to cooling and this is the main problem with replacing older units (with a new AC/heat pump) plus the newer 10 button Tstat. In 2010 I bought a new old style heat pump so I’d have a spare unit...been cheap insurance as it’s still in the box.

[hypoxia]

Good advice you are getting. Extremely rare for a compressor to go bad. If it is the reversing valve the valve coil is available, a cheap and easy repair. I have a rare earth magnet I use on top of the reversing valve to switch it when the coil fails although others have reported that did not work for them.

When you say it blows hot air does it blow warm ambient air or HOT heat pump air? Just want to make sure there's no misunderstanding regarding the reversing valve.

128º F in Death Valley today if that makes you feel any better about the Las Vegas 114º today. It's a dry heat everyone from the East tells me

[jacwjames]

Here is a troubleshooting guide for my Duotherm AC heat pumps. There is a section on the reversing valve
Also attached is a parts page for my AC, item 7 is the solenoid valve.
Here is a source but might be available via a RV shop.
https://www.dyersonline.com/dometic-...rness-kit.html

[vito.a]

I had the same thing happen to our bedroom heat pump.
I just couldn't get the exterior magnets to reverse the flow.
I was able to purchase a new reversing coil ($52) and it was easy to install, just two wires.

Email from Dometic Customer Service
Dometic Heat Pump model number is: 630515-321
Thank you for contacting Dometic. The part number for the solenoid coil harness is 3310714.005. Note that the valve itself is not replaceable, only the solenoid harness.
Jon
CustomerSupportCenter
Phone (800)544-4881
customersupportcenter@dometic.com

https://www.ebay.com/itm/OEM-Dometic...gAAOSwUKxYhmxP

[Hoss7]

Thanks for all the replies! Just to be clear, it blows HOT air - not just ambient air. The ambient air is around 105* and it'll blow air over 130*. Would this indicate that it's indeed the reversing valve?

If I'm understanding the schematic in the PDF above, is the reversing valve (also called the solenoid valve?) accessible in the roof air unit from the roof once you unscrew the plastic cover? (Ie NOT from inside the coach in the ceiling where the filters are located)

Does any common RV shops tend to sell a replacement reversing valve so that I can buy locally and get this fixed?

Thanks!

[jacwjames]

The 130 F air is a good indicator the reversing valve has quit.

You are correct, the reversing valve is accessible by removing the shroud. Once the shroud is off just follow the copper lines from the compressor and the reversing valve is mounted on it.

You will have to determine the right number for your reversing valve, there should be name plate information on the AC unit for the Make/Model/SN. You might be able to find a parts schematic on line or do a search using the model number.

You might have luck finding this locally once you get the part number. If not they can order and expedite shipping, or find it on line and shipped to where your are.



Mine was an easy fix as the wire controlling the reversing valve had come come loose and contacted the tubing causing it to quit working. Fixed the wire, secured it so it wouldn't move, and the problem was fixed.

[Ivylog]

You are not replacing the actual valve... just the 120V coil. Unhook the 2 wires going to it and check for resistance... probably less than 20 ohms if it’s good. Hopefully it’s open as replacing the relay is difficult... probably a new control board will be easier.