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Author Topic: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold  (Read 1997 times)

Bob Stone

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Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« on: July 19, 2021, 01:58:25 AM »
Recent very hot camping trip the front A/C unit decided on it's own to blow very hot instead of cold air. When I checked the unit on the roof the tubes coming from the compressor are one side hot the other cold. Very cold air is blowing out of the vent holes on the side of the roof cowling and very hot air is blowing into the RV through the ceiling vents. It's operating as if it is in heat pump mode. I have reset the CCC and received the FF response to no avail.


The rear A/C, identical to the front one operates as normal.
Any suggestions much appreciated. Thanks
Bob Stone
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Bob Stone
'05 Monterey Laguna IV  Cat C-9

Fred Brooks

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #1 on: July 19, 2021, 02:08:19 AM »
   Bob, the reversing valve is stuck in the "heat pump" mode up on the side of the air conditioner. You may try tapping on it when you turn it on. Good luck, Fred
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Fred & Cindy Brooks
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Bob Stone

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #2 on: July 19, 2021, 06:53:46 AM »
Thank you Fred I'll certainly give that a try. When I had the cover off and found the tubing to be appropriately hot and cold I noticed a little gizmo that resembled a relay and possibly a valve. I did in fact tap it which may have made difference because once I had the top all buttoned up the vent felt like it was starting to cool briefly then it resumed belching out heat again.


Is that a solenoid that operates the valve? Does the system have to be compromised to replace the reversing valve? Thanks again Fred that certainly describes the problem. Besides tapping do you have any other possible suggestions should tapping not be successful?


Bob


Addendum: I’ve now watched the many YouTube videos on reversing valves and unless the gently tapping works the prognosis does not look good. Also I must check the pilot valve coil. 🤞
« Last Edit: July 19, 2021, 02:36:14 PM by Bob Stone »
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Bob Stone
'05 Monterey Laguna IV  Cat C-9

Fred Brooks

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #3 on: July 19, 2021, 03:15:26 PM »
    Bob,
Unfortunately these air conditioners are considered disposable. Life expectancy is 12 to 15 years. If you have a friend in the HVAC business, you may be able to add a freon "line tap" to evacuate the system, replace the reversing valve, leak test and then recharge the A/C. From my experience, don't waste your time or money on an older air conditioner. There are no air conditioners available right now because of covid and the unbearable hot weather the country has been experiencing. If you can find one, don't let them rip you off because there are a lot of desperate full-timers out there looking for one. Hope you get it resolved the fear-mongering ramps up, Blessings, Fred
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Fred & Cindy Brooks
2000 Marquis, Jasper
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2014 Honda CRV
Proverbs 3: 5 & 6

Bob Stone

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #4 on: July 19, 2021, 07:38:55 PM »
Thanks again Fred, fortunately the rear A/C is still functioning. I seldom used both so if need be I may just switch the front with the back one for the time being. It's unfortunate that these A/Cs are not more easily repairable for such a simple problem. Built in obsolescence.


Bob
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Bob Stone
'05 Monterey Laguna IV  Cat C-9

Fred Brooks

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #5 on: July 20, 2021, 01:11:19 AM »
     Bob,
In the event you choose to do that, take a picture of the "dip switch" settings on each of the PC boards on each respective air conditioner so you can change them to reflect the new location., Fred
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Fred & Cindy Brooks
2000 Marquis, Jasper
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2014 Honda CRV
Proverbs 3: 5 & 6
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Darrell Terry

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #6 on: July 20, 2021, 03:32:10 PM »
Bob,
I had the same condition last summer while in Redmond,OR.
I replaced the reversing solonoid and it works fine now.
Mine was pretty easy to diagnose as there was a large crack in the solonoid.
Darrell Terry
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Darrell Terry

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Re: Front Dometic 15K A/C-Heat Pump Blows Hot instead of cold
« Reply #7 on: July 20, 2021, 04:34:10 PM »
Picture of damaged solonoid
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2004 Monterey
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