Mitsubishi Mr. Slim Thermostat Problem, I Think

[Gene Griffin]

I have a Mitsubishi a Mr. Slim Mini Split System. The indoor air handler unit is a ducted SEZ-KD12NA, Serial #99M00519 and the outdoor heat pump is a SUZ-KA12NA, Serial #02P00028. The thermostat is a PAR-21MAA . I can set the thermostat at 63 degrees on "heat mode" and the unit will remain on heat and not shut off, even when a bulb thermometer is showing 80 degrees. The thermostat temperature will show something in the neighborhood of 68 degrees. Anyone have any idea #1 why the thermostat gives a incorrect temp reading and #2 why the thermostat temp exceeds the thermostat set temp without shutting off.

 

[WyrTwister]

Hard wired tstat ?

Is that tstat approved by the manufacturer for that model of MS ?

God bless
Wyr

 

[Gene Griffin]

Wyr,
It is hard wired. The one original with the unit was a Mitsubishi PAR-21MAA-K. Since I was having an identical problem with the original one that came with the unit, I bought a replacement thermostat PAR-21MAAU-J to replace it, but the problem remains.
Gene

 

[WyrTwister]

Does it have an internal tstat you can drop back to ?

God bless
Wyr

 

[Gene Griffin]

Wyr,,
Not sure, because HVAC is not my line of work, but I will look over the schematics.
Gene

 

[WyrTwister]

If you can access internal set up software , you may be able to turn things off and on ?

Or disconnect the external tstat & power cycle the unit ( look for jumpers that may need to moved ) .


God bless
Wyr