3 ton A/C compressor ohm readings

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Old 09-07-19, 01:25 PM
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3 ton A/C compressor ohm readings

Have a single phase 230v compressor in outdoor condenser unit. Breakers tripping fuses blowing, no start condition. No humming. Isolated to compressor. New Contactor and capacitor. Taking ohm readings on compressor terminals Iím getting 0.8, 20, 20.8. The values add up correctly but the C-S seem quite high. Can someone help me diagnose based on these values? Would this indicate a short in the windings? Is the high resistance an indication that the compressor is shot or should i be looking elsewhere? Thank you!
 
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Old 09-07-19, 01:30 PM
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Welcome to the forums.

In addition to your measurements posted..... did you check from all three wires to ground ?

The .8 is basically a short.
What does your meter register when you short the two leads ? Probably close to .8 ohms.
 
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Old 09-07-19, 02:38 PM
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Check to ground. May have a grounded compressor.
 
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Old 09-07-19, 07:51 PM
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Yes two leads read .8 dropping to 0. Iím going to take another reading just in case but i did do two already. No short to ground. Any options besides new compressor? Are the coils serviceable? Thank you for the welcome!
 
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Old 09-07-19, 07:58 PM
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No, not serviceable.
To get to the internals the refrigerant must be reclaimed, the compressor removed and the shell must be physically cut open.
They are referred to as hermetic, or a non-serviceable style of compressor.
 
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Old 09-07-19, 09:25 PM
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It would appear the start windings are burned but not shorted to ground. When the resistance gets that low there is no recovery other than replacing the compressor.

Based on system age you need to weigh the cost of replacement of the compressor against replacing the entire condenser.
 
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Old 09-08-19, 04:14 AM
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The system is an old R22 Comfortmaker setup. Eight years ago, I was told it was shot and that I needed a new system. Back then i did my first HVAC DIY and only had to replace the fan motor. Itís been fine until now. I just cross referenced the Bristol (Benchmark) compressor number and found a replacement for about $500.00. Not sure how much a charge of R22 would cost. New condenser I suppose i would have to find an r22 to match up with my air handler? Otherwise a whole new system which Iím not looking forward too. Thank you for your assistance; much appreciated.
 
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Old 09-08-19, 04:34 AM
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Hi, does the unit have a crankcase heater, any readings from the compressor terminals to ground?
Geo
 
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Old 09-08-19, 07:03 AM
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Bristol is out of business.
You’ll have to reclaim the existing charge. It can be tested for acid to see if reuse is an option. If not the refrigerant will have to be recycled.
You’ll need a torch. And vacuum pump.
Refrigerant prices vary. But there are alternatives to R22.
 
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Old 09-08-19, 01:05 PM
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At this point...... you are beyond a DIY repair. Special equipment is needed to capture the refrigerant.
 
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Old 09-08-19, 04:38 PM
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No crankcase heater or short to ground. I can buy a recovery tank and manifold for $100.00 so Iím thinking Iím still in diy zone. I think with a new compressor, recovery tank and manifold, and gas, i would be in around $800.00 or perhaps a bit less. Can possibly buy used r22 condenser for less.
 
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Old 09-08-19, 04:52 PM
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Youíd still need a reclaim machine, vacuum pump, nitrogen, micron gauge.
The refrigerant may not be reusable which youíd have to find somewhere to turn in the bottle to.
New R407C condensers are available. But may not work well with old evaporators.
Iíd not suggest used equipment. Iíve seen many get burned doing such a thing.
 
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Old 09-08-19, 05:11 PM
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Oh I see. That might get a little pricey. Back to the drawing board I guess.
 
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Old 09-08-19, 05:36 PM
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Refrigerant isn’t going on the reclaim tank by itself, it needs to be pumped in.
The tank needs a vacuum pulled in it to remove noncondensables.
Used tanks sold via eBay and such tend to be heavily contaminated and shouldn’t be used for anything other then refrigerant headed to the recycling center. If you use one you’ll risk contaminating your system which causes all sorts of major problems.
Once completed the system should be pressure tested and needs to have a vacuum pulled below 500 microns.
If you recycle the refrigerant you’ll have to show your epa certification card.
 
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