Question about Mitsubishi MSZ09UN Air Conditioner

2 Answers

Outdoor unit stops and starts every 5 to 10 minutes

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  • gautd Mar 24, 2011

    Gas charge has been checked and reported ok. The behavior is erratic. Sometimes the machine will run for 45 mins, then the outdoor unit will stop, re-start after around 5 mins, run for maybe 10 mins, stop again and then continue this stop-start cycle. At other times, the outdoor unit stops very soon after the machine is started. I did notice that the outdoor to indoor cable is of 3 cores and, so, there is no ground conductor between outdoor and indoor units. The machine is a Mitsubishi Starmex Single Split Non-inverter unit.

  • gautd Mar 24, 2011

    The filters, coils, etc.are clean and there is no dirt around. The machine is relatively new - about 9 months since installation.

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2 Answers

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  • Master
  • 2,047 Answers

This s seldom normal with Air conditioning units to stop and restart at periodic intervals usually it is as a result of the temperature of the unit which fluctuates. The thermostat is always responsible for this function as it regulates at what temperature the unit cuts of power to ensure the life of the unit lasts quite a while.
Bt if the time at which the cut off takes place is shorter than usual then this is a sign that the thermostat is becoming weak and would need replacement as the level of heat resistance it can take has reduced. This diagnosis is a general one with air conditioners so get an expert to identify the location of the thermostat so you can order a replacement part for it.
Hope this solution has been helpful?

Posted on Mar 24, 2011

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  • Mitsubishi Master
  • 43,501 Answers

Hi,
The most common cause for the unit to cycle like that would be a low charge situation.
If you are low on freon the unit will cutout on low pressure and then when off the pressure will go back up and the cycle starts all over agian.....
Get a certified professional to check the unit out and fix the leak so that once recharged the unit will hold the freon.
The most common place for them to leak is the piping connection behind the indoor unit...although it could be the connection at the outdoor unit also...
These are flare connections and they can and do loosen up over time from the vibration...

heatman101

Posted on Mar 24, 2011

  • D. Floyd Kolb
    D. Floyd Kolb Mar 24, 2011

    No the calce should not be the problem, but the next thing that I would check would be to take off the thermistor that is on the indoor coil... this tells it to stop, then the coil warms and it restarts...this is to keep the indoor coil from freezing to a block of ice...

    Either the indoor coil is running too cold or the thermistor is bad...

    Make sure the air filter for the indoor unit is clean and that the coils are not plugged with dirt...there needs to be good air flow through the indoor coil...

    by removing the thermistor and pulling it away from the coil a bit you can tell if this is what is causing your problem...



    heatman101

  • D. Floyd Kolb
    D. Floyd Kolb Mar 24, 2011

    I would be suspecting the thermistor on the indoor coil...

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Art cool keeps stopping


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- Out of range thermistor sensor in both return air and freeze up sensor can cause the tripping “off “ the unit. The resistance of both thermistor is 8 to 10k ohms, so can test by using ohm meter

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