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grumpa8637

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Not knowing much about these, and trying to troubleshoot. The unit is a Goodman, model GSC140361AA. Think I'm dealing with a locked rotor situation but will describe my findings to this point. When unit starts, fan motor runs fine but there is a hum from the compressor that comes and goes about every 5 minutes. It's sealed so can't see shaft. Making use of a borrowed "Fieldpiece" HS35 multimeter with power disconnected; the dual capacitor shows correct dual mfd ratings, compressor windings show 1.7ohms between the common & run winding, 1ohms between common & start windings, 2ohms between the run & start windings, no short from any one lead to ground. With power restored and using clamp on, compressor run winding is at 60A & start winding is at 4A. So here's where I'm unsure, is the start so quick that I don't see the 60A on the start winding? Thought I'd see it on both or the start rather than run. Additionally, not understanding capacitor operation, capacitor shows 340V to fan and only 120V to compressor. The capacitor is a "dual" type with a 370V rating, what should I be seeing on these? Any help or suggestion greatly appreciated.
 
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One-eyed Jack

Senior Member
Location
Scotland Neck, NC
grumpa8637 said:
Not knowing much about these, and trying to troubleshoot. The unit is a Goodman, model GSC140361AA. Think I'm dealing with a locked rotor situation but will describe my findings to this point. When unit starts, fan motor runs fine but there is a hum from the compressor that comes and goes about every 5 minutes. It's sealed so can't see shaft. Making use of a borrowed "Fieldpiece" HS35 multimeter with power disconnected; the dual capacitor shows correct dual mfd ratings, compressor windings show 1.7ohms between the common & run winding, 1ohms between common & start windings, 2ohms between the run & start windings, no short from any one lead to ground. With power restored and using clamp on, compressor run winding is at 60A & start winding is at 4A. So here's where I'm unsure, is the start so quick that I don't see the 60A on the start winding? Thought I'd see it on both or the start rather than run. Additionally, not understanding capacitor operation, capacitor shows 340V to fan and only 120V to compressor. The capacitor is a "dual" type with a 370V rating, what should I be seeing on these? Any help or suggestion greatly appreciated.
Click to expand...

You could try something like this.
http://www.arnoldservice.com/compressor_hard_start_boosters.htm
 
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wptski

Senior Member
Location
Warren, MI
ptonsparky said:
Normally these types of capacitors will bulge somewhat when they fail. Look at the end where connections are made. Replacing it should take care of the locked rotor condition. If not, new units are much more efficient.
Click to expand...
More efficient, yes but how many years does it take to break even? Even HVAC people don't agree with some of the claims made! People these days just don't have the extra money to replace instead of repair. In order to qualify to a tax credit, use get >SEER 16, I believe but your exsisting duct work may not be able to handle it and therefore be less efficient.

I just recently had a problem with a large dehumidifier. The compressor like is like a AC unit and uses a PCS motor. During my search I found it mentioned the fact that both PCS motor windings are the same and therefore easily reversable. This for some reason doesn't hold true with these sealed compressor/motor units. Of course, these need/must only run in one direction but I never read anything pointing this out.
 
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Mgraw

Senior Member
Location
Opelousas, Louisiana
Occupation
Electrician
I would check the capacitor first. Disconnect power then use an old screwdriver to short out the common and compressor terminal on the capacitor. Remove the compressor wire on the capacitor. Then use a capacitor tester to check it. If you don't have a capacitor meter you can use an anolog ohm meter. Touch the common and compressor terminal. The meter should jump up and then bleed down. If not swap the leads on the terminals. If it doesn't jump up and then bleed down the capacitor is bad. If the capacitor is good then try a hard start capacitor such as the one on post #2.
 
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sbe

Member
Based upon your compressor winding resistance readings, the start winding is partially shorted (turn to turn) because in these types of PSC compressor motors the start winding resistance is always higher than the run winding. The compressor is most likely mechanically stuck/frozen, and through repeated attempts at starting has begun to overheat & burn out the start winding thus resulting in the low start winding resistance reading. The compressor requires replacement and the cause for the stuck/frozen motor must be determined. Possible causes are liquid refrigerant flood back from a defective TXV, dirty indoor coil, etc. washing out the lubrication oil in the sump of the compressor, shortage of refrigerant, adding refrigerant to this system without repairing the refrigerant leaks could result in loss of lubrication oil as well. Hope this helps...

Howie
 
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