[mymechi]

Ok... I know better... but since I was dealing with low voltage... I figured no harm... WRONG! :eek: I should have turned off the breaker when replacing my thermostat... enough said. I replaced my thermostat (simple comfort 3001) with a honeywell RTH6300b because the simple comfort display was jittering off and on, but still working. Anyway, when disconnecting the wires I noticed a small spark. :cool: DUH!. After replacing it with the honeywell, no power. I mean the display was there, but it has batteries so that's that. But no fan would come on. I then switched back to the old one (no batteries), and nothing. Not even a display. The wires out of the wall are red to R/RH,white to W,yellow to Y,green to G and blue to B. That's how it was connected to the old one as well... (the letters to the codes.) Connecting to the honeywell I did the same except that the blue wire, I was instructed by the manual to tape off because I have gas heat/ac. Not needed. My question is, blown transformer or is there a fuse that might have blown? Also location of both to check. Air handler I know, in the garage up high :o (oh boy)... but where abouts?
Thanks, chuck

[labman]

The first step is to check for 24 volts between the red and blue wire. If it is dead, the transformer may be too unless it is protected by a fuse. The fuse is likely near the transformer, either in line, or on a nearby control board. They are usually in the furnace. Follow the red and blue wires back to it. One little spark shouldn't burn up the transformer. With luck, it is a fuse.

[mymechi]

Thanks, I'll try and locate to see if it is indeed a fuse (which I hope) and let you know!
Chuck

[mymechi]

That was the ticket! Blown 3amp fuse on control board inside air handler.
Thanks "LABMAN"... you r da man! :D chuck