Lennox Compressor Help Needed

[helpmefixit]

My Lennox HS25-651-1P compressor has stopped working. Here is the stroy:
- Thermostat turns on attic furnace/blower unit.
- Outside comprssor does not go on.
- Tested and replaced 60A fuses at comprssor.
- Tested and confirmed power to input side of relay in compressor (240V, 1P)
- It appears that there is power at thermostat leads in compressor (only setting on multimeter that displayed reading was DC milli volts as my meter does not have AC milli volt setting).
- With everything connected and thermostat on the relay is not connecting and compressor does not go on.
- There is visible rodent damage on wire casing to capicitor but wire is not chewed through, only casing is gone and wire is not touching any metal.

My thoughts are as follows:
- power is not getting to relay to activate it (switching problem)
- defective relay.
- capacitor problem?

Please reply iwth any suggestions for diagnosis/repari.

Thank you...

 

[glennjanie]

Welcome HelpMeFixIt:
One quick diagnostic practice is to take your screwdriver and push in on the center of the contactor and see if the compressor comes on. Also, while you're at the contactor, locate two small wires on the side of it and check them for 24v. Those wires activate a magnetic coil to pull the contactor in.
Now, turn the power off and take the little hood off the side of the compressor where the wires go in and see if all the wires are still connected; they are bad about burning off over the years. Next, take all the wires off the compressor and find three terminals marked S, R and C; take a digital ohmmeter and check from C to S, then C to R, then S to R. The first two readings added together should equal the third reading. If that is not true, the compressor is burned out.
Let us know how you come out and if we can help any farther.
Glenn

 

[helpmefixit]

Thank you for your reply. First, it appears that the relay/contactor cannot be pushed in manually as you describe. I do know what you are speaking of and there is no place to push in to make contact. Second, do you mean capacitor or compressor when you are speaking of checking the three contacts. There are three wires contcted to the capacitor as you describe. Thank you in advance for your reply.

 

[helpmefixit]

Glenn,
OK I have an update. I located the compressor wires and tested as you stated. The results are as follows: C-S=2.2, C-R=1.1 and S-R=2.5. Does this indicate a failed compressor. I then removed the relay cover plate and exposed the contacts. With the compressor wires reattached I pushed the contactor and the unit came on. The fan did not start at first but I then started the blades spinning with a screwdriver and the motor powered up and began spinning the fan. I let the unit run for about 60 seconds and then when I released the contactor the compressor made a slight ticking noise. What would you suggest next. It appears that the problem is at start up. Thanks, Jeff

 

[helpmefixit]

Glenn,
Well I went back to the unit to check the power to the contacts. I had my son turn the thermostat on and the unit started on its own. The fan needed a jump start but the unit is running and A/C is working. Maybe the contacts or some of the connections were just dirty. Anything to suggest to keep it working?
Thanks,
Jeff

 

[helpmefixit]

Compressor ran for about 30 min. and then stopped. Contactor was still connected and humming. Shut off at thermostat and dont know what to do next.