Mitsubishi Electric - PUH-3VKA Fault

[rude]

Hey guys

Got called out to this unit today and was told someone had already changed the compressor capacitor 2 weeks ago and now the unit cuts out after running for 30 mins.

So i checked it out and found the compressor getting very hot and the unit drawing 16.8A. The name plate suggested the unit should be running at 14.6A.

I took air on temperature on the condenser and that was 37degrees C. Air off was about 48 degrees C. I also took the suction pressure and that was sitting around 480kpa suction pipe didnt really feel that cold either. Indoor Return Air temp was around 30 degrees C

After the unit was running for about 30mins it cut out and fault starting flashing on LD7 - RT overheat protection.

Now what i want to know is that fault related to the compressor over heating? And what is causing it to overheat? Could it have been the capactior that has failed caused the compressor to fail as well?

Thanks

Alex

[install monkey]

was the fault history cleared when the capacitor was replaced? is the capacitor the correct size? LD7 Over heat protection l The thermistor is broken.
l Coil temperature is over
153°F.
l Measure the resistance of the thermistor.
l Check the outdoor fan motor.
l Check if air cycle is short-cycled

[rude]

Apparently the 1st fault was a P8 fault on the controller. He has put a 60uf cap in im unsure if that is the correct size. I pressed SW2 to see if it had fault history but no LED lights lit up.

-I didnt check the thermistor but wouldnt the unit fault straight away if it was faulty?.
-Outdoor fan motor was running continuously so i dont think that was the issue.
-Condenser air isn't short cycling. Altho ambient temps are getting up to 42 degress C (107f)

[install monkey]

http://www.mediafire.com/view/?2144r90escf9ccg service manual, cant find any info regarding the capacitor size, dirty contacts on the contactor can cause higher running currents

[rude]

Thanks for that my unit is a Ducted unit tho but info should still be relevent.

Looks like maybe that pipe thermistor might be reading a bit higher than it actually is. I might pull it out of the condenser and see if the unit runs longer.

[install monkey]

in the manual it states about reading the outdoor coil sensor bit, by adjusting the 2 tiny dipswitches and reading the binary led display- prove its reading correctly
Apparently the 1st fault was a P8 fault on the controller. He has put a 60uf cap in im unsure if that is the correct size. I pressed SW2 to see if it had fault history but no LED lights lit up.

-I didnt check the thermistor but wouldnt the unit fault straight away if it was faulty?.
-Outdoor fan motor was running continuously so i dont think that was the issue.
-Condenser air isn't short cycling. Altho ambient temps are getting up to 42 degress C (107f)

[rude]

I went back yesterday to check the sensor and when i opened up the unit the compressor was tripped on internal overload. I might try convince the customer to replace the whole unit