I hope someone can help I must be over looking something. Heil gas furnace single stage heat and cool. I did not have 24 volts at the transformer (i did have 120 on primary) so I replaced the transformer. I now have 24 volts yet no voltage on the t-state terminals of the board so I replaced the board. hooked up all the wires double check powered up and blow the 5 amp fuse. (thank god for the fuse). I then removed all low voltage wires replaced fuse powered up and everything is ok. Installed low voltage wires fuse blows. I removed the thermostat replace fuse powered up everything OK. Put R & W together heat works fine. So I thought must be t-stat replaced stat confirmed wires on computer board and stat powered up and blow the fuse. I then removed Y & G from stat replaced fuse powered up and heat works perfect.
Any idea why when Y & G are hooked on the stat up I am blowing fuses ? I even un hook low voltage to condensor. Really need help thanks anyone.