Ductless Air Conditioning Unit - Blogs & Forums On Residential HVAC AC & Heat Systems

Blog Title: transformer for air conditioner burns up

Main Que: My 24 volt transformer continues to burn up. This is the second transformer. What could be the problem?

  • Category:
  • Query By: CASSANDRA SWANSON (Stagecoach, SC)
  • Date: 07/24/2015

Answer: Most of the time it ends up blowing the fuse on the board if you have one, instead of the transformer. I usually suspect the thermostat wires as the problem, but other devices with coils and electronics can cause the problem. I had a reversing valve coil cause this problem one time. Most of the time it is in the wiring. This is a pain and time consuming, but in order to find the problem I would turn off all the power, take all the low voltage thermostat wires loose from the thermostat, air handler, and outdoor unit. I would take a digital meter set to ohms and check between all the wires with the meter. You should not get a reading between any two wires if the wires are in good shape. If the wires are good you would need to test the components from each wire or terminal to ground. The meter should not move. This is a pain sometimes finding the problem. Many times I would find the problem where the wires were installed going through the furnace body. The thermostat wires would ground out on the furnace body. The vibration of the furnace or air handler over time had torn through the wire insulation and caused a short. Sometimes animals will chew through the wires and cause a short. Sometimes sun light on the wires over time will rot the insulation and short out the wires.

  • Replied By: DEREK DAVIDSON (Bellevue, CA)
  • Replied Date: 08/08/2015