Help! - The blower on my HVAC system continuously runs, even when ...

HOMEOWNER CRIES FOR HELP...

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

QUESTION:
The blower on my HVAC system continuously runs, even when I turn the system off. I have a Trane XE78 furnace with a White Rodgers 50A50-405 controller. Any ideas on what's wrong?

ANSWER: You will have to do a couple of things to determine where to look first, if you take your thermostat off the wall and the wires are separate on a thermostat subbase and the fan stops then your stat is bad if the wires are still together with the fan switch or if your stat has no subbase and is wired on the back remove the green wire if the fan stops your stat is bad, if it continues to run you will have to look at the furnace shut off the power and remove the green wire from wherever it is connected and turn the power back on if the fan is still running then the problem is with whatever device controls the fan it will either be a pc board where the fan relay is integral to the board and the board will have to be replaced or a fan limit switch, you can check the plunger on the front of it to make sure it is not pushed in if it is in the right position the fan/limit will have to be replaced or a seperate fan relay which will have to be replaced.