I have an older Carrier 58gs and I recently bought a Honeywell thermostat RTH8500 wifi unit. The thermostat was relatively easy to hook up and worked fine this winter. I went to turn on the air recently and the outside fan works but the interior blower does not. The thermostat wiring is R to R; W to W; Y to Y and C to C. My furnace is wired R to R; W to W; Y pig tailed to the red wire on the low voltage transducer and C was on either GC or GH or was it Y...darn it (I don't recall). The white wire off the transducer is on the C terminal. Honeywells customer support said to "move the G wire to the C terminal at the thermostat (which was previously done), then move the G wire to the C terminal at the furnace, and then place a jumper wire between the Y terminal and the (now empty) G terminal at the furnace." Because I don't recall if I was on GC or GH, I may be jumping incorrectly. I did a test and a relay sparked more than a relay should. Any advice?

 

Welcome to the forums.

Gc = fan/cooling
Gh = fan/heating

So you would use a jumper from Gc to Y.