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Old 06-08-2017, 17:08   #1
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Dometic A/C Compressor Locked

Hi. I have a new Dometic 16,000 BTU A/C that was installed about one year ago but has only approximately 6 weeks of running on it thus far.
I live in South Florida and use it for weekend trips occasionally and when we go to the Bahamas.
all was working well during our 3 week trip to the Bahamas this past month where it essentially ran continuously for 4 weeks.
I left it running when we returned home while the boat was cleaned and emptied from the trip.
One morning about 10:30 it shut off and showed the error code "HPF" on the display. I looked this up in the manual and it says the unit shuts down the compressor mainly when water flow is insufficient.
So the next day I replaced the water pump and the unit started up and pumped water like crazy - for 5 minutes then shut down again with the same errorcode. When Restarted it immediately went to errorcode.

Looking through the manual further I noticed that the unit works as long as the seawater temp is lower than 90 degrees F. I checked the depth sounder on the bridge and sure enough 91.8 F. Ok so I let it sit over night and checked the water temp first thing in the AM and it was 88.4F so I tried a restart but no go. Within a few seconds the unit shuts down and codes out the same "HPF".

I'm looking for suggestions at this point - maybe a master reset - or a procedure to unlock a locked compressor.
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Old 06-08-2017, 17:22   #2
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Re: Dometic A/C Compressor Locked

A high pressure fault and shutdown usually involves low cooling water flow, double check to be sure that the seawater is flowing well. Also, a problem in the expansion valve may also cause this . Check to see if the small capillary tube on the sensing bulb isn't broken off at either end. A goggle search for TXV or Thermal Expansion Valve should show you what to look for. Try rapping on the TXV also.
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Old 06-08-2017, 17:35   #3
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Dometic A/C Compressor Locked

It may be the the water cooling system needs flushing with acid as it can get a lot of growth in it.
Why did you replace the water pump, was it not working? I suspect you now have a spare water pump, which is not a bad thing to have.
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Old 06-08-2017, 18:45   #4
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Re: Dometic A/C Compressor Locked

Run Barnacle Buster thru it...
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Old 06-08-2017, 19:46   #5
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Re: Dometic A/C Compressor Locked

Thanks for the suggestions. As this is a "new" installation and my water flow through the side of the boat is phenomenal I am really sure that the system is clean. I do use Barnacle Buster on the heat exchanger system from time to time but not on the A/C as yet.
I'm curious about the expansion valve so I'll check that out.
You are right I do now have a spare pump.
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Old 06-08-2017, 21:29   #6
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Re: Dometic A/C Compressor Locked

should still be under warranty, why not just call the installer?
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Old 06-08-2017, 21:42   #7
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Re: Dometic A/C Compressor Locked

Is the compressor not running at all as in totally "locked"? Or does the compressor run for some seconds and then fault with high pressure (HPF)? You can tell if it is totally locked as it will draw a lot of current and usually trip a breaker. Your description doesn't sound like a locked compressor.

If the water temp around the boat is really 88F then it might simply be too hot for a liquid cooled air conditioner. And just because there is lots of flow does not mean there is lots of cooling. Gunk can build up on the inside of the condenser coil loop and prevent heat transfer. You can have lots of water flow but the condenser can still be too hot and cause an HP fault.
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Old 07-08-2017, 05:19   #8
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Re: Dometic A/C Compressor Locked

Probably not a warranty item as I purchased the A/C in July of 2014 and dis not install it until Fall of 2015. I did the install myself as it was a replacement for a previous Dometic unit and it was pretty much just remove and hook back up to the same connections and hoses and duct work.

There is a service business here in town and I do business with them but thought that maybe it was something simple that I could take care of. After 40 years of going back and forth to the Bahamas I have learned that it to be able to take care of as much as possible myself as you never know when things can happen when on a trip away from US based service personnel.

The exterior of the expansion valve looks ok with nothing broken and tapping on it made no difference.

Yes it now goes straight to fault - at first it would run for a few seconds then faullt. Water temp is now in the 80's after an overnight rain.
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Old 07-08-2017, 06:22   #9
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Re: Dometic A/C Compressor Locked

It may be as simple as too much refrigerant gas. When water temps get up to 90F it becomes important to have exactly the right amount. If too much then over pressure happens more often. I would ask the local service people to take a look. Their gauges will tell the story pretty quickly.
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Old 07-08-2017, 06:23   #10
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Re: Dometic A/C Compressor Locked

Quote:
Originally Posted by transmitterdan View Post
It may be as simple as too much refrigerant gas. When water temps get up to 90F it becomes important to have exactly the right amount. If too much then over pressure happens more often. I would ask the local service people to take a look. Their gauges will tell the story pretty quickly.
I wrote before seeing your last post. It could be a faulty high pressure switch. Still would be a good idea to have an experienced tech have a look.
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Old 07-08-2017, 09:33   #11
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Re: Dometic A/C Compressor Locked

Just to eliminate water temp as a possible problem, I'd hook it up to a water hose and run it.
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Old 07-08-2017, 11:50   #12
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Re: Dometic A/C Compressor Locked

Have you checked your sea water filter? I find that the flow looks good even though there is a lot of crud built up on the filter. If that is OK I would backflush the cooling system before calling the repairman.
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Old 07-08-2017, 13:07   #13
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Re: Dometic A/C Compressor Locked

Thanks all. I did flush system with water and cleaned strainer first off. Plugged pump into electrical outlet and had great water flow. Contacted Dometic support and they suggested it may be high pressure switch and suggested I Jump it's contacts and see if unit runs. If so then replace High Pressure Switch. Says its a simple screw/Out and new one back in - but quickly to minimise gas loss.
I'll let you know after I try this test.
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Old 07-08-2017, 13:50   #14
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Re: Dometic A/C Compressor Locked

We've got a Cruisair 16k split system. Our boat is in Sanford, Florida, on Lake Monroe. Fresh water.. so you'd think we'd never have to flush our cooling system. au contraire. Exactly the same error condition as you describe. We flush the system with city water running backwards through the condensor every three months or more often in the summer. A ton of black crud comes out when we flush it. Makes a huge difference in cooling temperature even if we aren't getting the HPF error and shut down yet. A good check is to just put your hand on the condenser loop. Ours, when working right, is hot to the touch but we can hold onto it. If it needs flushing I can hardly touch it. It will always be hot immediately after the compressor, but cooler as it exits the cooling loop.

Good luck. AC in Florida is very important!
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Old 09-08-2017, 11:20   #15
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Re: Dometic A/C Compressor Locked

I also have a dometic16k. First time display read locked it was clogged sea strainer. Which you already checked and cleaned. The second time after cleaning the sea strainer I left air between strainer and pump. Again read locked on display. If you need a marine tech i would recommend Andy
9548659654. He's very noligble and professional. I'm in north Miami. Good luck
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