Question about Mitsubishi Mr. Slim MXZ30TN Air Conditioner

1 Answer

Pressure in both lines fluctuate from 140psi to below 30psi

System shuts down @ night wont restart , I guess because of  high pressure , so i let out some gas until the system starts , it runs , andthe lines are cold but the air is only cool not cold, @ this point the systemruns @ 70 psi ,  then at night it shuts down and the pressure goes up to 140 again then it won't start again . to make things more complex the system is straight from japan and does not crossrefrence with any U.S. models.  it is a mr. slim style ,  outside compressor is the inverter type , with 2 inside units ,    can anyone help??

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  • j saum
    j saum May 22, 2009

    on this unit we only have low side ports to attach the gauges to (no high side ports)  

  • Farley Redfield
    Farley Redfield May 11, 2010

    Can you tell me what an inverter is? AC-DC??

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  • 462 Answers

The foreign made market is different than the USA.

First if the unit doesn't get a change or input from a manual command (on the remote on mine) it will shut off because it assumes there is no one there.

2nd if it is in the timer mode it may be different in orientation than what you are used to looking at.

TO make sure these are not your problem review the instructions.

If this is R22 or R410A there is not a pressure switch that will cut it "OFF" at 140#. And if your fluctuating tween 30 and 140 It is almost sure its low on charge especially if its new. Now I assume you mean 140 on the high side, right?

Posted on May 14, 2009

  • Farley Redfield
    Farley Redfield May 23, 2009

    If you have just low side access you now may have the origonal problem plus be low on gas. Never remove or add refrigerant unless your measuring it by weight. This is the only dependable way you have of knowing about where the charge is.



    Look on the copper lines leaving the compressor. If you find a switch firmly ancored or screwed into either line, with 2 wires and you see no clips holding the body down these are most likely the pressure switches. The wires used on most are blue but they could be any color.

  • Farley Redfield
    Farley Redfield May 26, 2009

    Because your only reading on the low side this fluctuation means even less to me now. Without a high side access it will be more difficult to help you reach a correct and speedy diagnosis.

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