I have an 8-year old Lennox Signature heat pump. It has been working fine, but it has recently developed a problem. The outside compressor unit will not come on. The air handler seems to work fine, but the outdoor unit shows no signs of working. The fan does not spin, and the unit does not make any noise. We are currently in AC mode.
I've tried a few very basic diagnostics. The first thing I did was to reset the circuit breakers at both the main house panel and at the air handler. The other thing I tried was to change over to heat mode and kick up the set temperature to see if it might be an AC only problem. Neither thing worked.
The funny thing is that SOMETIMES it will come on. On Friday, I noticed the house warming up despite the air handler running. It was then that I noticed the outside unit was not doing anything. I reset the breakers, turned the entire system off for a few hours, started it back up, and it worked. It seemed to have worked throughout the day Saturday until mid-afternoon, then it crapped out again. It hasn't worked since, and it is Sunday morning here.
My thought for today is to open up the thermostat (Honeywell programmable) and check for loose wires. If everything looks okay there, I was going to cut the power to the system and open up the cover to the outside unit and air handler. I'll look for loose wires there also.
Other than that, I'm out of ideas. Since I cannot hear any sounds comping from the outside unit at all, I'm wondering if it is even getting power. Is there a fuse somewhere I can check, or maybe another breaker that is not obvious? I don't mind getting my hands a little dirty, but I don't wan to start digging around and end up getting surprised by a fully charged capacitor or something like that.
Turn the system to cool then go outside and look at a few things. The defrost control board has 2 lights used for diagnostics , the key chart is printed right on the board. What does it say? Is the capacitor swollen or leaking? Does the contactor pull in after the 5 minute time delay? If so is there any noise from the compressor? Are there fuses in the outside disconnect?
Outside of those basics you'll need a meter. Actually I'd recommend all home owners who intend to do DIY repair to purchase a good multimeter.