Hello

I have just bought a house with central AC and I have never had it before in any other home. The unit is not working (Lennox HS29 outside and Lennox CB30M-41-1P inside). I have tried all the thermostats, flipped the fuses, and installed a filter (there was none in the unit). If I set the thermostats to "fan" the inside unit kicks on, but I can't get the outside unit to come on at all. I have absolutely no experience with HVAC but I would like to at least try to troubleshoot before I call someone out. Any suggestions?

Thanks
Brianna

 

Brianna,

I don't know how comfortable you are working around electricity, so if you don't feel comfortable with any of these steps, just stop and call a professional.

On the outside unit (compressor), remove the panel that covers the wiring (don't know where that is on your unit). You'll see what is called a contactor. It's rectangular, usually black, with several wires plugged onto it at each end. The contactor is actually a relay. When the thermostat calls for cooling, it sends 24VAC to the low voltage side of the contactor. This activates an electromagnet which pulls down the contacts, which sends 240V to the compressor & outside fan motor. With the power to the system turned off, try to locate the contactor. Using a nonconducting tool (piece of plastic or wood), press on the contacts. You should feel & hear a "click" as the sets of contacts connect.

Now that you've found the contactor, turn the power on and watch to see if the contactor clicks and the contacts connect (as they did when you manually pushed the contacts together). Make sure that before you do this, the thermostat is calling for cooling and has fresh batteries. If you're alone and don't have a helper (much easier with a helper), try using your insulated tool (plastic or wood) and momentarily push down on the contactor to make the contacts close. If you hear the compressor & fan start up, either your contactor is bad, or you have a wiring problem (broken or shorted low voltage wire either in the house or going out to the outside unit). To troubleshoot further, you'll need a voltmeter (and know how to use it).

 

Thanks Bob! This is a bit out of my league so I am just going to call in a professional. I really appreciate your input!

Brianna