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Old 04-28-2011, 03:01 PM   #1
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Lennox Crank case heater


How do you test the heater?

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Old 04-28-2011, 03:34 PM   #2
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You can test like resistor. If you heat the thermistor to the specified temperature the sensor will open the circuit.

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Old 04-28-2011, 03:40 PM   #3
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How do you test the heater?
You can ohm it, check the amp draw, and make sure you have voltage to it.

Why do you need to check it??? Problems???
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Old 04-28-2011, 07:05 PM   #4
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If it has voltage to it, and it's not on almost 100% it's bad. Like others said check to see if it drawing amps.
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Old 04-28-2011, 08:22 PM   #5
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I did what you suggested and it is working. My unit looked like it had a power surge. The contactor was fried and I changed that, The power to the compressor was melted and I replaced that, I check the ohms on the compress and it checks out good. What elese could it be? If I disconnect the compressor wires and force the contactor on the fan runs, When the compressor wires are connected it trips the circuit breaker. Any suggestions
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Old 04-28-2011, 08:34 PM   #6
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Check for continuity between the compressor terminals and one of the copper pipes. Sounds like the compressor or one of the compressor wires is shorted to ground.
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Old 04-28-2011, 08:43 PM   #7
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MAKE ABSOLUTELY SURE that you DO NOT touch any part of the outdoor unit while testing it. If the compressor is shorted to ground and you touch the condensor YOU become the ground and could DIE.

Pay attention to this story JJ.
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Old 04-28-2011, 08:54 PM   #8
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Quote:
Originally Posted by newtech View Post
You can ohm it, check the amp draw, and make sure you have voltage to it.

Why do you need to check it??? Problems???
I did what you suggested and it is working. My unit looked like it had a power surge. The contactor was fried and I changed that, The power to the compressor was melted and I replaced that, I check the ohms on the compress and it checks out good. What elese could it be? If I disconnect the compressor wires and force the contactor on the fan runs, When the compressor wires are connected it trips the circuit breaker. Any suggestions
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Old 04-28-2011, 08:57 PM   #9
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Originally Posted by Marty S. View Post
Check for continuity between the compressor terminals and one of the copper pipes. Sounds like the compressor or one of the compressor wires is shorted to ground.
I have continuity.
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Old 04-28-2011, 09:07 PM   #10
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Quote:
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MAKE ABSOLUTELY SURE that you DO NOT touch any part of the outdoor unit while testing it. If the compressor is shorted to ground and you touch the condensor YOU become the ground and could DIE.

Pay attention to this story JJ.


Now I see how this test can be dangerous. Thanks yuri for showing me this.
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Old 04-28-2011, 09:09 PM   #11
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I have continuity.
You need to replace your compressor
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Old 04-28-2011, 09:52 PM   #12
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Quote:
Originally Posted by wayne1178 View Post
I did what you suggested and it is working. My unit looked like it had a power surge. The contactor was fried and I changed that, The power to the compressor was melted and I replaced that, I check the ohms on the compress and it checks out good. What elese could it be? If I disconnect the compressor wires and force the contactor on the fan runs, When the compressor wires are connected it trips the circuit breaker. Any suggestions
With all power OFF. And all wires removed from the compressor. When you check the compressor for continuity, check across R and C, S and C, and then R and S. R and S ohm value should equal the sum of the other 2 values.

Next, check from each of the compressor terminals to ground(one of the copper lines attached to the compressor is best), if anyone of them has continuity, the compressor is shorted to ground, and needs replaced. If n one of them do. Check that the run cap is not shorted to ground.

Its possible your compressor has a winding to winding short. That type of short can easily weld the contactor's contacts together, and heat it up enough to look like it was struck by lightening.
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Old 04-28-2011, 10:15 PM   #13
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JJ and Wayne. BE VERY careful with a stalled/shorted compressor it can develop TREMENDOUS heat inside the compressor and literally blow the white "fusite" plug where the C/S/R terminals attach to the compressor out and you could get blasted with high pressure refrigerant/smoke/burning acidic oil/phosgene gas as it burns up. I have seen this several times and I am sure Beenthere has also. It WILL NOT give you any warning it is blowing, (sometimes makes a growling sound but not always) you DO NOT want to be anywhere near that plug or have your face near it.
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Old 04-28-2011, 10:22 PM   #14
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And when it blows, if the cover isn't on, it can take a flame and the oil will come out like a blow torch was in the compressor. And if you are infront of it, you probably won't survive the burns.
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Old 04-28-2011, 10:36 PM   #15
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Just to illustrate what can happen ...... adding oil, refrigerant, etc.


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