Heating, Air Conditioning, Fridge, HVAC/AC won't turn on


More than a year ago my Trane XB80 air handler quit working. We could hear the click in the control panel when it was supposed to come on, but nothing else happened. The company that installed the unit came out and got it going a few times, and it worked anywhere from a month or so to a couple of days. They told us that it was an electrical problem in the house. After hiring electricians to replace all the wiring to the unit, it still did not work. Then, the company told us that we'd have to replace the whole unit. Not having the money to do that, we've been living with window units since.

About two weeks ago, we had a major electrical storm with a lightning strike very near the house. During that storm, the air unit came on and worked well and normally for about two weeks. It has now stopped again. Given that the electrical storm got it going again, I'm thinking the problem may be a short or something much less serious than the company led us to believe.

Do you have any idea where we might begin looking for the problem? I intend to bring in a professional since I know nothing about it, but based on my past experience, I'd like to have some idea of what the problem may be.

110/120 volts of electric power goes from the electric breaker panel into the air handler.
One 110 volt lead goes to the 24 volt transformer which reduces the 110 line voltage down to 24 volts low voltage.
24 volts goes to the thermostat(R wire connection), the thermostat distributes the 24 volts to different controls depending on what it is set to.
If the thermostat is set to cool and the temperature indicator is set low enough for the cooling to come on the thermostat sends the R wire 24 volts to the Y wire, the Y wire carry's the 24 volts to the air handler control board, to the blower relay that turns the blower on, to the outside condenser contactor that turns the compressor on and starts the condenser fan motor.
When the thermostat calls for cooling if nothing happens, no outside unit activity, no air handler blower you need to check the thermostat by disconnecting the R and Y wires from the thermostat and twisting them together which will bypass the thermostat.
You need to check the low voltage wires and other control connections through the system, to see if they are getting 24 volt power when the wires R  and Y are twisted together.  

Heating, Air Conditioning, Fridge, HVAC

All Answers

Answers by Expert:

Ask Experts


Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

Hands on since 1950

©2017 About.com. All rights reserved.