Thumping noise in the compressor

[Husky250]

I had a call today regarding a thumping noise coming from a compressor. The guy never checked the compressor resistance. He suspected the Outdoor board and replaced it. The system ran for two weeks and failed again. He says he weighed refrigerant charge per the data plate with short run on piping. The system was installed two months ago. Elevation has not been exceeded. This got me to thinking about the megger suggestions you guys gave me. Could it be possible to have small short to ground and system run for for two weeks and take out the outdoor board again. I did recommend the voltage balance check as well as the diode check for the IPM. Im thinking a megger is needed in this situation. What you guys think?

[powell]

Husky,

I'm gonna simplify what I think your saying.

The thumping noise is the compressor short cycling or trying to start. The outdoor board is maybe an electronics control board. Is this an A/C or HP unit?

When you say failed again, are we talking about the board?

A compressor that short cycles or is hard starting will play havoc on the electrical controls, wiring, etc.

Check it while your there. Add a hard start kit if starting is the issue. If you see short cycling then your going to need to put the guages on it and find the cause.

Regards.............Powell

[praveen]

Was this compressor failure to start & giving jamming noise.Was oil present in te system.check compressor resistance(for grounding or earthing problem) & oil for acid test.

[Husky250]

Sorry for the lack of info: The compressor was trying to start. Its a DC Inverter system ( Sanyo ) On the call for cooling the outdoor fan would run but a thumping noise was coming from the compressor. He said resistance was equal across the windings. This happend before and he replaced the outdoor board. The system ran for two weeks and same thing happend again. System would try to start and thumping noise from the compressor. He described it as someone tapping the top of the compressor. He said he would test the compressor with a megger and get back to me

[The MG Pony]

Sound mechanical to me, did you try to listen with a stethoscope?

[powell]

The system ran for two weeks and same thing happend again. System would try to start and thumping noise from the compressor.

If the compressor ran for two weeks after the first repair then it should be ok.

Can you let us know what we are we dicussing here? HP, model of compressor, voltage at the job etc.

[Husky250]

H/P Sanyo Inverter system 12,000 BTU
Voltage = 118 v
Installed= 3/20/07
Not sure of compressor model number

[powell]

I'd check with Sanyo and get their recommended hard start kit. A solid state device would probably work ok, but check with them.

[Husky250]

Thanks alot !