15k a/c not cooling

[Wireman]

We're suppose to leave tomorrow for 4 days. Dealing with the fires here in Murrieta yesterday. Went through my checklist today and fired up the roof A/C.

It runs but no cold air. Thermostat seems to be working ok. It cycles thru the modes and changes temps. Had it set to 69 degrees to make sure it started.

Blower runs ok. Took both covers off, couldn't see any wiring issues. On the roof I verified the compressor is running and all the fins are clean. Just no cool air, basicly blowing ambient temp air.

I'm a fairly competent troubleshooter on alot of stuff but I'm no A/C expert.

I thought if a compressor is running, there is freon present. The compressor stays working and doesn't cycle on and off as would a car A/C if it was low on freon.

Temps in the 90's the next few days, so for the wife, A/C is needed.

Hopefully someone can point me in the right direction to get this figured out ASAP.

[Wireman]

I forgot to mention the unit. It's a Dometic 15K DuoTherm Brisk II

[Crabman]

I can't help you with the diagnosis but I can refer you to this thread on the FR forum which suggests the Dometic 15k has a problematic history. Several pages.....

Dometic 15,000 BTU A/C Failure - Forest River Forums

[djmikel]

Were you hooked up to at least a 30 amp circuit?

[Wireman]

Originally Posted by Crabman

I can't help you with the diagnosis but I can refer you to this thread on the FR forum which suggests the Dometic 15k has a problematic history. Several pages.....

Dometic 15,000 BTU A/C Failure - Forest River Forums

10-4 I'll check it out.

[Wireman]

Originally Posted by djmikel

Were you hooked up to at least a 30 amp circuit?

Yes, dedicated 30 amp RV outlet.

Unit worked last time plugged in at home and the RV park, approx. 2 months ago.

[Learner]

How do you know that the compressor is actually running? Do you hear it turn on, apart from the blower fan?

I had one day when the fan on my roof unit was working, and I could hear the thermostat activating the compressor relay, but I had no cold air. I also could not hear the compressor from inside the cabin, just the fan noise.

When I checked the AC breaker, I found that the compressor breaker had tripped. After resetting it, it worked fine and has not failed since then.

[Wireman]

Originally Posted by Learner

How do you know that the compressor is actually running? Do you hear it turn on, apart from the blower fan?

I had one day when the fan on my roof unit was working, and I could hear the thermostat activating the compressor relay, but I had no cold air. I also could not hear the compressor from inside the cabin, just the fan noise.

When I checked the AC breaker, I found that the compressor breaker had tripped. After resetting it, it worked fine and has not failed since then.

I took the A/C cover off on the roof. Had the wife turn on the A/C at the thermostat while I watched and felt the compressor.

As soon as she turned it on, the fan started and then above 5 seconds later the compressor kicked on. I could feel it and hear it when it started, no doubt in my mind.

For my unit there is only 1 single pole 20 amp breaker. Reset it a few times but still no cooling air. Breaker off, nothing works with the A/C.

I left a message with a mobile RV tech and he was kind enough to give me some tech advice on the phone.

Told him my situation with both the fan and compressor running but no cool air. He said I own a boat anchor now, it's junk and can't be repaired.

Freon leaked out somehow and basically it's a disposable item. A $650 disposable item as that's the cost I found for a new one on line.

I told him it's only 3 years old and the tag shows made in China. Quote: " that's the state of the RV industry now."

So at some point in the near future, I'll be ordering a new A/C unit. Same model and brand just to make the installation process as easy as possible.

[poohbear]

You really can not diagnos a compressor by the " touchy feally method " . Put a clamp-on ammeter on the " common " wire of the compressor and then tell us what it does at start up and for a short while after. 2nd, without adding a port to put a manifold guage on, don't know if or isn't refrigerant in the system. Call a hvac company that doesn't use a crystal ball to troubleshoot.

[Jopopsy]

If I had the opportunity to rid myself of a Dometic AC I’d get a Coleman any day of the week.

[Wireman]

Originally Posted by Jopopsy

If I had the opportunity to rid myself of a Dometic AC I’d get a Coleman any day of the week.

That's what a mobile RV tech just told me this evening.

[Wireman]

Originally Posted by poohbear

You really can not diagnos a compressor by the " touchy feally method " . Put a clamp-on ammeter on the " common " wire of the compressor and then tell us what it does at start up and for a short while after. 2nd, without adding a port to put a manifold guage on, don't know if or isn't refrigerant in the system. Call a hvac company that doesn't use a crystal ball to troubleshoot.

I measured across the 3 posts on the top of the compressor with a ohm meter.

Winding ohms are within spec per a RV A/C video on you tube by a RV tech.

I can feel the compressor vibrating when it kicks on and hear it running.
Maybe not scientific, but it is running. After a few minutes it's hotter than heck. The evaporator is not cold at all.

Per 2 mobile RV techs, after describing what the I told on this post, they both agree the unit is bad. Nothing is serviceable other than the start capacitor, motor and control board. Any compressor issues, a new unit is the only fix.

[poohbear]

the mobile rv tech needs the money.

[2edgesword]

There are ways to find leaks and tap into sealed units to recharge them but it's time consuming and the cost of parts a labor probably make replacing the unit the better option long term.

[Grumpy]

Originally Posted by Gary Roe

RV is my utmost companion. With the scorching summer rays hitting I hard, to make the ride pleasurable, I thought of turning on the AC. But, how cold should an RV Air Conditioner get?

Temperature differential, inside air temp vs air temp coming out of a/c, should be 15 to 20 degrees. That is the industry standard.

That does not mean the inside will get 20 degrees cooler than the outside air, it only means the a/c will drop the air temp going across the coil by 15 to 20 degrees.

[PaulB12]

Compressors are pumps. When you start and let run does the suction line get cold(big tube) and does the discharge get hot (little tube). If not you're not pumping. Unit probably toast. Things break.

PaulB12

[Nature Ist]

I went through this when my 2020 HT was 2 months old. Dealer replaced under warranty, but the long and short of it is the unit is not serviceable and if you tried to find the leak and add new refrigerant, it would cost the same as a complete new unit.
I wish it was possible to just replace the operating parts so you don't have to remove everything from the roof and re-seal it all.
From your description, you will not be able to repair that AC unit.