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BubbaT

Air Conditioner compressors locking up, killing AC unit

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I have a 2015 Winnebago Aspect 30J.  It has had 3 rooftop air conditioners (Coleman Mach 8 with heat pump / no heat strip) go bad, all because of  locked up compressors.  Winnebago, Coleman, three repair shops and I are all baffled. We have changed the circuit breakers, control box (inside the AC unit), checked voltages, etc. but the problem keeps repeating.  Works fine for a period of time (months) then fails to cool.  Diagnosis all the same:  locked up compressor.  I would appreciate any and all wisdom and suggestions.

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Do you have a surge protector & low-voltage protector when you're on shore power? Did these failures all occur while in the same campground? If so, any of your neighbors having a similar problem? Any other problems in the electrical system other than the a/c units that might be an indication that the problem is more global than the a/c systems themselves? Any loose wires/connections on the remote wired thermostat (if you have one?) Just a few scattered thoughts about this.

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When Coleman got involved, was it still under warranty?  Have they offered to change out compressors?  Never heard of 3 at the same time!!!

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https://community.fmca.com/profile/36588-manholt/

I am the second owner.  Coleman replaced twice under warranty.  I had to buy the most recent unit at full price.  Most expensive RV AC I know of.  Allow me to clarify.....The AC has been replaced 3X already.  It now needs replaced again.  Three units have been returned to Coleman for evaluation and they have found bad compressors (locked) in the last two.  I have yet to locate anyone who will change the compressor.  The compressor is made by Tecumseh and costs almost $300 (parts only).  I'm guessing labor would be another $200 or so.  Still far less than the $1200 for a new Mach 8 unit.

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Have voltage protection, no other electrical problems, thermostat wires / connections are good.  This has happened at different locations.  No apparent  problems reported from neighbors.  Everything else in the coach works fine.

 

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Thanks for the extra information - that helps eliminate some of the common outside issues as the cause. If I understand correctly, you've got three a/c units on this coach. Two of them have been fine the whole time but one of the three units on the roof has failed three times.

If this is the case, I'd really be suspicious of something specific to that unit's installation which is causing the problem. Could the thermostat be bad and causing a problem (malfunctioning so as to cause the a/c unit to short cycle or run too much, etc?) Has the thermostat for this unit been replaced along with the a/c unit? Perhaps there is a staple or screw somewhere in the wall that is intermittently causing a short in the wiring? The same unit failing over and over really screams that something is wrong specific to that install.

However, if you're saying that each of the three different a/c units on the roof have each failed separately (not the same one over and over again), then if this was my coach I'd be shopping for a different brand a/c unit. Most brands/models are interchangeable and mount in a standard 14x14 opening so unless there is something unique about the way they're installed on your model coach I would think that you could try something different.

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Check the running voltage at unit 

Check voltage at changeover valve as it defaults to heat 

Check voltage to contactor 

You may be getting just enough to close contactor but not enough to switch changeover valve completely some times which will cook compressor no flow no oil 

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I just looked up the spec sheet for your coach.  It came with one 15,000 btu AC, no heat pump or strip!  Does yours still have a vent in kitchen and bathroom?  I suspect bm02tj is correct in that your not getting enough voltage.  3 AC's draw a bunch of amps at start up.  Your Coleman Mach 8, come in 9,200 or 13,500 or 15,000 btu's...witch ones do you have and are they all the same btu's???

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4 hours ago, manholt said:

I just looked up the spec sheet for your coach.  It came with one 15,000 btu AC, no heat pump or strip!  Does yours still have a vent in kitchen and bathroom?  I suspect bm02tj is correct in that your not getting enough voltage.  3 AC's draw a bunch of amps at start up.  Your Coleman Mach 8, come in 9,200 or 13,500 or 15,000 btu's...witch ones do you have and are they all the same btu's???

Carl,

I read his initial post differently.  He said, "It has had 3 rooftop air conditioners (Coleman Mach 8 with heat pump / no heat strip) go bad, all because of  locked up compressors... three repair shops."

I read that as one A/C failed three times.

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Brett,

You are correct.  The coach has one AC unit.  Mach 8, 15000 BTU, with heat pump, no heat strip.  Something in the system has killed 4 AC units.  Cannot be all units having bad compressors.  Voltage at unit was fine.  New controller box.  ???????????  Perplexed.

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Bubba T, Welcome to the FMCA Forum !

Question, When your Units fail, are you running them in AC mode during the day and in the Heat mode during the evening ?  Like setting the temperature at 70 to 75 degrees - where the units would switch from cooling to heating ! When they tend to fail.

Rich.

         Airexcel makes a number of brands of Roof AC / Heat pump units.

Note! This link is supplied for use by an authorized service center. However ! it can prove helpful for owners that have AC / Heat Pump units installed on Horse Trailers to Class AD Motorhomes. The Video describes what information is need and where to find part numbers and readings needed to help expatiate service. 

           https://www.airxcel.com/coleman-mach/technical-service-videos

            https://www.airxcel.com/coleman-mach/service-support/model-number-changes

The PDF file on the in question in this post.

Air Excel_Coleman_ SERVICE MANUALS 1976665.pdf

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IT sounds like your evaporator my be freezing up.  Which will cause the oil in the compressor to boil out causing the compressor to  seize up. A couple of things that can cause this 1) thermostat set to low and a/c never gets to cycle off. 2) poor air flow filters pluged, too many vents closed, some kind of blockage in air flow.

 

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50 minutes ago, Mfhack01 said:

IT sounds like your evaporator my be freezing up.  Which will cause the oil in the compressor to boil out causing the compressor to  seize up. A couple of things that can cause this 1) thermostat set to low and a/c never gets to cycle off. 2) poor air flow filters pluged, too many vents closed, some kind of blockage in air flow.

 

What about a faulty thermostat or a short in the wiring (caused by a bad connection, bad wire, or staple/screw penetrating through where it shouldn't be)?

Not sure how any of the failed units ran long enough to have their filters clog up. The rig is only 3 years old. If the a/c is ducted, could there be a restriction in the ducting which is reducing airflow to below the critical flow point? Or possibly something was installed backwards from the factory during the initial a/c install which caused the flow restriction? If so, I bet that all the subsequent installs followed suit and never looked for that kind of problem.

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The Original Poster has not mentioned any information regarding a ducted system. Sounds like the RV has just a single Mach 8, 15000 BTU, with heat pump.

This Air Excel unit is a newer Low profile design, with 2 fans and is supposed to have the same low temperature cooling on both high and low speeds. The design sounds like it has a reversing solenoid that allows the units to transition from cooling to heating. 

The only items I can think of that would cause the compressors to fail on a total of 4 units is excessive head pressure - freeze up of the evaporator / cause ,could be the freeze protection circuit(this style circuit has been around for years on AC systems),but are both the condenser and the evaporator coils protected with this type circuit  or the transition Solenoid not being able to move the slide valve through a full travel /  OR the high pressure switch  /  Freeze switch  common relay coil is failing - or the contacts of the relay can not handle the compressor start current. The Fan motor and compressor motors both run through the relay contacts. The blower motor does not go through this relay.

The drawing of the electrical wiring does not show some parts that IMHO should be in the circuit to protect the system from counter EMF pules or high current surges from the starting and run capacitors. 

Tried to find any information on the number of recalls on this size and design, with no luck.

If the Original Poster has had this issue - there should be a number of other owners with the same issue 

Rich.

I'm totally aware that I have listed items beyond 99 + percent of RV owners skill sets or knowledge base.  

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It sure looks as if there is a restriction of some type happening, could be  in the duct work, but I'm betting that there is a design flaw with the reversing valve design on this brand unit. Were it I, I would be looking for a different brand. Three strikes your out in my book.

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The single a/c unit on this coach has gone bad multiple times. Something is wrong here, and I'm and I'm wondering if it is a problem with the install. Could have been done wrong at the factory, who knows. While I love to blame the manufacturer as much as the next guy, this many units failing one after the other really says that there is something wrong in the RV itself.

This is a ducted a/c from what I can see online. Was the ducting done properly to allow for proper air flow to/from the a/c unit? Perhaps a shorting or failing thermostat is causing the unit to run constantly or fight against itself. Perhaps a loose connection on the 120v wiring causing a low-voltage situation. But, something is not right here as there is no good reason for this many units to go bad one after the other.

OR...

There could be a serious problem with the Coleman Mach 8 a/c units. I just did a quick look on Google and apparently there are many entries about this particular unit. Seems like others are having repeat failures as well.

IF everything checks out in the coach itself and all wiring is in good shape, then I'd vote for bailing on the Coleman and putting in something else. We had an Atwood Air Command with heat pump on our coach last year and it seemed to work fine. I'm sure that there are many other options as well.

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Been looking Also Richard ! There is a higher then I would expect issue or failure rate. 

This is some information covering a high on / off cycle rate on the units, But no mention of seized compressor .

                                          Generally with what you have described, I would look for the location of the sensing tube for the manual thermostat.  The end of the sensing tube should be hovering right over the filter.  If it is close to the evaporator coil, or close to the supply air chute, it could be sensing the colder temperature, and shutting the compressor down prematurely.  Also, if the room temperature is near 65°F, the thermostat may be shutting it down normally.  The lowest point that thermostat will run is right around 65.   Interesting.

Let me know what you find.

Eric Botts
Technical Assistance Coordinator
RV Products, a division of Airxcel, Inc.

Eric should be a lot closer then we are though

Rich

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When you get a new unit hook up four volt meters and two temp gauges.

You need voltage at compressor, fan relay, change over valve and compressor contactor; and temp drop to confirm.

Anyone of these can cause the problem.

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