Help! - Could use some expert help here. I tried to help a neighbo...

HOMEOWNER CRIES FOR HELP...

posted: September 8th, 2008 - 2:04pm

QUESTION:
Could use some expert help here. I tried to help a neighbor who had trouble installing a new thermostat. He didnt turn off the power to the system and short circuited the wiring in the process. Then of course nothing worked.
The system is a Bryant forced air heater in the attic with a split a/c system with the compressor outside the house. The Forced air unit is a Bryant model number 310JAV048090 made in 2003. I found the 3 amp fuse on the control board blown and after rewiring the thermostat correctly and replacing the fuse powered the system back up. The heater works, but the A/C does not. I can go out side and push the contacts on the outside A/C unit and it runs fine. There is 28 volts coming out of the control board in a few locations and trying to put the system in to test doesn't seem to work. The fan will not come on manually only with the heater on. There doesn't seem to be any low voltage power on the cooling side or the fan. I tried jumping from the common 24v to Y, is that a correct thing to do? Nothing happens. Do I need a new control board or does the blowing of the fuse protect it from damage?

ANSWER: It sounds like we burned up the board and the fan relay is bad but you can get this unit up temporarily while you acquire parts the cooling function does not need the board so tie the yellow wires together and this should bring the condensor on then power the black wire for the fan in the furnace to the line voltage black at either the door switch of the board and the fan will run constant until you can get a new board.
Before you make all these assumptions though shut the power off take off the thermostat wires at the stat tie the r,g and y wires together, turn the power back on and see what happens.
If it works now then you got a problem with the stat or the way it is hooked up.