Question about Dometic Rooftop RV Air Conditioner

7 Answers

Dometic 15,000 BTU Rooftop A/C for RV

Three year old a/c cools but before it reaches proper set temp, the compressor seems to stop with a shudder, then the fan blows in extremely high gear for about 45 seconds. After a few minutes the a/c/ begins again. We have another one in front of rig that never does this.

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  • kamper2 Aug 11, 2008

    I could not find a definitive model number but specification sheet indicates my two units are one of these two model #s 620526.321 or 620526.326. Both units are ducted and both work off the Comfort Control Center. I was a bit of a step ahead of you in making notes to what as happening, although perhaps not to the degree you suggested. Does the following info help?

    8/9/08 @ 7:20 pm Excellent 50 Amp service with Hughes Autoformer Mini Transformer

    A/C was set to 73 degrees

    The outside temp was 83 degrees

    The inside temperature was 75.9 with humidity inside at 33%

    The unit's compressor cut off with a shudder

    The fan kicks into high gear and blows hard (without compressor the air is barely cool)

    The fan blows by itself for 45 seconds and then stops altogether

    The whole unit restarts both the compressor and fan at once within 2 minutes (without any human intervention)

    Removed shroud but allowed unit's insulation to stay in place and waited for the malfunction to reoccur. ( It did within 10 minutes)

    Removed the insulation at the moment the malfunction reoccurred and viewed that from what could be seen - the coils were not freezing up.

    Note: Just prior to the malfunction, the second a/c unit in front of fifth wheel kicked on and was functioning (as it always does) properly.

    To rule out possibility that the malfunction had anything to do with the second unit powering up. The seond unit was completely turned off.

    After 10 minutes, the unit cycled off properly (no incidence of the compressor stopping first followed by the fan in high gear ) but it powered up again within 2 minutes.

    Doubtful that it ever reached the temp set on comfort control thermostat at the time it kicked off -since it kicks back on in less than 2 minutes.

    Several times after turning off the bedroom unit - the main unit cycled off without incident but within an increase of three tenths of a degree and within 2 minutes it cycled on again.

    Now, after open the cover and looking at unit on roof - but doing nothing - it seems to be working properly.


  • kamper2 Aug 14, 2008

    Thankful to all who wrote in and has suggestions to try. We have tried them all and feel the main problem is simply that the unit is short cycling. Will pay for professional help and will share our results once we get issue resolved.

  • kamper2 Aug 14, 2008

    As of 8/14/08, I have paid $9.99 for email expert assistance. I wish only to add to the above information, that we have monitored our problem for over 36 hours now and have found a consistent pattern of one a/c unit where the compressor runs 10 minutes and then shuts down for 3 minutes and then restarts. When maximum temp of the day ourtside is reached, we have the additional problem of the fan running for 50 seconds past the time the compressor quits. Still the 10/3 minute cycles. Other a/c unit not affected at all. It takes the unit all day to reach the set temp on the CCC since it never stays on any longer than ten minutes before shutting down for 3 minutes.

    We have turned off all fluorescent lights and computer router as once person suggested it could be RF waves. No change and we doubted it would since the other unit is not affected.

    I could not find a definitive model number but specification sheet
    indicates my two units are one of these two model #s 620526.321 or
    620526.326.


  • kamper2 Aug 14, 2008

    I am unsure I am properly reporting my problem. I paid for the $9.99 Premium email assistance but unsure who is answering my questions about my Dometic Rooftop AC/Heat Pump Penguin that has only a 10 minute compressor running cycle then a 3 minute off cycle nm matter what the CCC temp is set at. Will I get the solutions I paid for or are you saying you can't help after I just paid $9.99? What am I doing wrong?

  • kamper2 Aug 14, 2008

    I just keep getting, "Good Luck" remarks from responders to my problem. Will someone be posting an actual solution? What did I pay $9.99 for if all I get are people saying "o.k. and good luck"?

  • kamper2 Aug 14, 2008

    Dear Techexpert12

    You say I need ventilation for my unit outside but how can it not be getting proper ventilation if it is sitting outside on top of my R.V. with nothing around it and no trees or obstructions. If this indeed were the case, why would it not have done this the first 3 years I had it?

  • kamper2 Aug 14, 2008

    I keep getting advice about proper ventilation of the unit. I assure
    you it is well maintained and properly ventilated. The unit has no
    obstructions and no damage to the fins or blower. The blower is
    running but compressor still shutsdown every 10 minutes and restarts 3
    minutes later. The unit is on top of our r.v. with no trees around and
    the temperature outside is 87 degrees. Since the rig is in full sun, I
    am sure it feels a lot hotter on top of the roof. Yet, these a/c units
    should be designed to handle this. If the heat build up in the unit
    can cause a shutdown, what other reasons are there for this heat build
    up besides ventilation (since I feel it has plenty of ventilation).?

  • kamper2 Aug 14, 2008

    I keep getting advice about proper ventilation of the unit. I assure you it is well maintained and properly ventilated. The unit has no obstructions and no damage to the fins or blower. The blower is running but compressor still shutsdown every 10 minutes and restarts 3 minutes later. The unit is on top of our r.v. with no trees around and the temperature outside is 87 degrees. Since the rig is in full sun, I am sure it feels a lot hotter on top of the roof. Yet, these a/c units should be designed to handle this. If the heat build up in the unit can cause a shutdown, what other reasons are there for this heat build up besides ventilation (since I feel it has plenty of ventilation).?

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Nice tries every body but i gues the problem is about proper place sir u just shud change the place wherte u set the A/C

Posted on Aug 14, 2008

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The machine has three main parts. They are a compressor, a condenser and an evaporator.
The working fluid arrives at the compressor as a cool, low-pressure gas. The compressor squeezes the fluid.
The working fluid leaves the compressor as a hot, high pressure gas and flows into the condenser.
A blower (electric) blows air to condenser coils to lower compressed cas temp and convert it in liquid. Blower's Air output must be free flow to have satified result, otherwise temperature arise and control sensor stops compressor's operation.

Posted on Aug 14, 2008

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Ensure that heated by compressed freon coils are well ventilated and blower is running. If their temperature goes high causes compressor to stop and remain stopped until temperature goes at acceptable range.

Posted on Aug 14, 2008

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The fan runs but there's no cold air?Is the air conditioner completely dead? See section 1. Is the thermostat knob turned to the proper setting? Is the compressor motor running? The compressor is a football-sized case with no apparent moving parts. It is located inside the air conditioner at the center. Is it humming or making any kind of continuous noise or causing the lights to dim? If it is making a continuous noise, and your air conditioner is still not cooling at all, there may be a serious problem with one or more of these areas:

  • Compressor


  • Condenser


  • Evaporator


These items are not user serviceable. You will need to contact a qualified appliance repair technician to repair these components.

If the compressor is not running but you do have power to the air conditioner there may be a problem in one or more of these areas:

  • Compressor


  • Overload and/or relay


  • Thermostat (Open thermostat)


  • Burnt wiring


  • Bad selector switch


  • Capacitor
  • Posted on Aug 14, 2008

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    Sorry to know that no 1 answered ur question.
    ok after reading n going through ur problem.i wud just like to tell u that u r hunting on a wrong side to find out wat the problem is.

    actually i find that unit is completely okay but its not getting a proper place to throw out the hot air outside because maybe ur ac is fitted in a very congested place were it cannot receive proper n enough fresh air to ventilate.so it gets hot n compressor turns down off to come back to its normal state.again it starts but same thing repeats n compressor goes of again. it will carry on till u place or get ur unit fitted on a proper place where it can get enough fresh air for ventilations. nothging to worry much .thanks.
    pls do rate the solution if it helps u know ur problem n solve it.

    Posted on Aug 14, 2008

    • tech expert12 Aug 14, 2008

      pls refer my solution sir and very sorry for the inconvininceyou are facing from others.

    • tech expert12 Aug 14, 2008

      as the unit is old it starts this type of problem later.

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    Okay good...good luck

    Posted on Aug 14, 2008

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    • 319 Answers

    Excellent,

    Good luck and let us know!

    Posted on Aug 14, 2008

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