I have an old janitrol air handler/electric furnace (240 volt) that is frying the transformer. The A/C unit is brand new - Goodman. I have installed a brand new thermostat(Honeywell), pulled new thermostat wire, pulled new control wire to the A/C unit outside, installed inline fuses on both wires on the 24 volt side of transformer. But, I am still frying transformers. I also found out that the "heating/off/cooling" switch on the new thermostat is getting hot when switched in the "cooling" position and that I had blown both fuses on the 240 side of the transformer during my last transformer fry. Does anyone know what the problem could be?

Sounds like your thermostat might be wired incorrectly or a relay is shorted.

HVAC1000 Please Help! My thermostat is wired exactly as my old thermostat was (4 wires Red, White, Yellow, Green). I installed it last year with the new A/C. Do you know which relay is likely to cause this? I done a little more troubleshooting today and I found my transformer is burning on the 240 side before blowing the 6.5 amp fuses. I also have a relay problem with the furnace elements, the furnace heats when the thermostat is in the cooling position but my transformer problem is happening when there is no power to the heating elements.

You have major wiring or electrical issues. I am sorry but you are there and I am not. It is just about impossible to sort this kind of problem out by posting here. Because of the electrical aspect of this situation I highly suggest you call a HVAC professional before you damage something else by trying to fix it.


New unit, thermostat, and new wiring opens up way to many possibilities.Sorry