View Full Version : How do I jumper a TX500B Thermostat, bypass the therm. To see if it's working?
krbowers
Jan 13, 2010, 08:17 PM
I hear the thermastat click when I raise the setpoint above the measured temp, but nothing happens. I want to jumper out the therm. just to eliminate it as the problem.
From left to right - I have G, Y, W, RH & RC - there is a jumper from RH to RC, with a red wire connected. I do read 28 VAC from R to W
KISS
Jan 13, 2010, 08:23 PM
Call the jumped Rh/Rc connection R
R to G turns on inside fan only
R to Y turns on outdoor unit only
R to W; turns on heat; furnace controls the fan if oil or gas heat.
If you measure 28 V from R to W on a call for heat, then the thermostat is not working.
krbowers
Jan 13, 2010, 08:51 PM
Call the jumped Rh/Rc connection R
R to G turns on inside fan only
R to Y turns on outdoor unit only
R to W; turns on heat; furnace controls the fan if oil or gas heat.
If you measure 28 V from R to W on a call for heat, then the thermostat is not working.
No voltage R to W on call for heat and jumpering R to W does nothing - thermostat is OK?
KISS
Jan 13, 2010, 08:58 PM
Right. On call for heat the voltage would be 0; On a no call for heat 28V or so.
Thermostat is OK.
What about R to G?
Try to do the R to W at the furnace and watch what happens.
Ignitor, pilot, burner, fan
Any codes set?
Unless the furnace has a standing pilot and limit controls.
krbowers
Jan 13, 2010, 09:28 PM
Right. On call for heat the voltage would be 0; On a no call for heat 28V or so.
Thermostat is OK.
What about R to G?
Try to do the R to W at the furnace and watch what happens.
Ignitor, pilot, burner, fan
Any codes set?
Unless the furnace has a standing pilot and limit controls.
I'm not sure I know enough to go any farther. I have a furnace in my attic - I took the covers off it and jumpered R to W - it came on. But I think that may just be the furnace for my upstairs, which works. I appreciate your help, but I'll probably have to call a repairman tomorrow.
KISS
Jan 13, 2010, 10:03 PM
OK, report back.
builderbob1
Jan 14, 2010, 12:34 AM
If you jump out or connect red and white wire at thermostat and the furnace comes on the thermostat is bad . Turn your thermostat fan control on your thermostatto the on position for a constand fan, if it runs you have 24 volts. If not check your breaker or toggle switch on side of furnace it maybe bad. If no 24 volts check circuit board or transformer