Forum Discussion

Charlie_D_'s avatar
Charlie_D_
Explorer
Oct 08, 2016

A/C

Dometic 15000 BTU. When running the compressor will drop off line. Sometimes after dropping off it will instantly come back on.

This happened on a trip a few weeks ago and then quit cooling. I do not know if the compressor was running when it quit cooling but I don't think it was. I normally run the fan on auto but changed it to High just to see if the coils perhaps iced up. Getting late so I shut it off for the night. Next morning started it up and it ran normally for a few hours while breaking down to move.

Just started it up in the driveway and it sounded fine. Ran it a couple of minutes the compressor dropped off and then instantly restarted. Turned unit off. Thirty minutes later I restarted and it is running fine after 45 minutes. Amp on wires running to the compressor.

Red-5.3
White-8.7
Blue 10.7
Voltage is good and steady at campground and home.
Motor start capacitor has a square device plugged onto it that says: "Motor starter WSX-7"
Compressor is quite, discharge line cold and sweaty but no ice.
Ideas?

Edited to say: 4 years old and has original Dometic digital thermostat.

11 Replies

  • Charlie_D_'s avatar
    Charlie_D_
    Explorer
    Oct 18, 2016
    time2roll wrote:
    Regular thermostat will not work. This one has a digital signal to the control box up in the ceiling in addition to 12v power. Furnace control is up there also.

    Here is my conversion to use this digital. May help see how it works.
    http://forums.woodalls.com/index.cfm/fuseaction/thread/tid/26820366.cfm


    Not looking for a regular thermostat. This is an LCD and I have found a replacement on Amazon. There are also others with a control bos. Unless something is wrong with the control box I would not need a new one. The bottom of the AC is covered by a 3 light pendant and I would have to remove the entire cover to replace the control box.
    My question is: Does anyone think the thermostat is bad according the the operating description I have posted?
  • Charlie_D_'s avatar
    Charlie_D_
    Explorer
    Oct 18, 2016
    I am reopening this post with a bit of other info.

    Ran the unit today. After a while the fan dropped off and then immediately back on. Had other things to do bit after 4 hours, went in and the unit was running and the unit was cooling and near it's set point. When I turned it to the "OFF" position the compressor quit and the fan continued to run as it should. After 5 minutes the fan was still running so I put the thermostat in the "off" position. It ran for a few minutes and then shutdown as it should. Thermostat fan speed was in AUTO. There does not appear to be any difference in the fan speed or sound when put in the HI or Lo. position.

    Dies it sound like a thermostat problem? If so, would a normal thermostat work? I see 3 wires. Orange, white and red.

    There thermostat is the original Dometic LCD.
  • Charlie_D_'s avatar
    Charlie_D_
    Explorer
    Oct 10, 2016
    smkettner wrote:
    Charlie D. wrote:
    Edited to say: 4 years old and has original Dometic digital thermostat.
    Is the fan set to automatic? I have a Dometic single station digital and when the air conditioner switches from low to high or high to low fan speed it does seem to turn off and back on within a brief moment. I believe above 3 to 5 degrees of the set point the air runs on hi and as it approaches the set point will switch to low. I have also experienced it when it will cycle up and down a bit before it decides to stay hi or stay low.

    I am calling normal even if a bit quirky.


    Set to AUTO. Yes, supposed to run high when temps are hot and then switch to low. Next time I turn it on I will set to HI to see if it will run without the sudden change. I have also heard the fan shut down for several seconds and the compressor continue to run which I believe is the change in speeds.

    Turned it on and after about 15 minutes the fan seemed to hesitate. If it actually stopped and restarted I was unable to tell. It then ran for another 2 hours without any hesitation. I was unable to tell if the compressor cycled but I definitely heard the fan cycle over a split second.

    Does anyone know if a run capacitor would allow that to happen? I checked all connections and the capacitors looked fine.
  • time2roll's avatar
    time2roll
    Nomad
    Oct 10, 2016
    Charlie D. wrote:
    Edited to say: 4 years old and has original Dometic digital thermostat.
    Is the fan set to automatic? I have a Dometic single station digital and when the air conditioner switches from low to high or high to low fan speed it does seem to turn off and back on within a brief moment. I believe above 3 to 5 degrees of the set point the air runs on hi and as it approaches the set point will switch to low. I have also experienced it when it will cycle up and down a bit before it decides to stay hi or stay low.

    I am calling normal even if a bit quirky.
  • Charlie_D_'s avatar
    Charlie_D_
    Explorer
    Oct 10, 2016
    How would one determine if the run capacitor is functioning properly. Would replacement be an advantage?
  • dougrainer's avatar
    dougrainer
    Nomad
    Oct 09, 2016
    sdianel wrote:
    a tech told us to leave the fans on "high" at all times in hot or humid weather. He said that the unit needs the air flow to prevent icing which will shut down the compressor. Since we have been doing that our 2 AC's have been working fine. If you have 2 AC's both fans must be on high. You can also try a thermostat reset. (in your manual).


    1. IF you have wall Tstats then that so called Tech does not know what he is talking about. Wall tstat controlled units have FREEZE thermistors that prevent freezing is ALL conditions. If you have ceiling mount controls(manual knobs) then what he states is correct.
    2. Thermostat resets have NO bearing on operational problems. ALL a reset does is communicate with each AC control board to determine how each board is programmed. Doug
  • sdianel_-acct_c's avatar
    sdianel_-acct_c
    Explorer
    Oct 08, 2016
    a tech told us to leave the fans on "high" at all times in hot or humid weather. He said that the unit needs the air flow to prevent icing which will shut down the compressor. Since we have been doing that our 2 AC's have been working fine. If you have 2 AC's both fans must be on high. You can also try a thermostat reset. (in your manual).
  • Charlie_D_'s avatar
    Charlie_D_
    Explorer
    Oct 08, 2016
    Doug-I removed "after a couple of minutes". In a few occasions the fan has continued to run, compressor drops off and then several minutes later it will restart without the fan ever shutting off and the thermostat fan speed set to Auto..

    Upon starting the AC after it has been off the fan will come on, run for a short time before compressor comes on and remaining on after the compressor has satisfied the thermostat then shut off. The instructions say that is normal.
  • dougrainer's avatar
    dougrainer
    Nomad
    Oct 08, 2016
    Your post does NOT make sense.

    "Sometimes after dropping off it will instantly come back on".
    "Ran it a couple of minutes the compressor dropped off and then instantly restarted after a couple of minutes".

    So which is it? INSTANTLY or AFTER A FEW MINUTES?????????
    IF after a few minutes and you have a WALL tstat it may be the Freeze Thermister in the wrong location or defective. It could also be a Overload switch on the compressor, but not likely. Your amps draws show a good unit. Doug

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