Have HVAC Questions? Ask an HVAC Expert for Answers
Does your thermostat have a "fan on" switch? If so what does the furnace do when you turn the fan on? By the way...this is for info only so no charge to get info.
It has a fan on or an "auto" switch, but the furnace will not cut in on either setting
Ok, this means there is no power to the furnace, or a bad trans former. Can you check to see if the breaker is ok or maybe a fuse in the switch on the side of the furnace? Sounds like we just need to get power.
I have two furnaces on the same breaker, and it looks like the same switch. This is a new house to me, built in 1980, and one furnace looks newer than the other.
I have a DVOM, maybe I will try to find out if there is power to the motor
Yes, it has both
I tested the switch..ok..checked the box it feeds to..connectors are fed power, and it appears to be ok to there. I could not access the wire at the motor, but the wiring looks good. I tapped on the motor to see if maybe the brushes were sticking, but nothing
Ok, so the blower started with the fan switch in the furnace?
If you feel comfortable with it, I can tell you how to proceed.
but the burner should come on and run, then after the blower does not run it would shut off on limit.
Can you remove the cover on that fan/limit switch and look at the round dial with numbers on it?
If you take the top cover off where the burners are, there should be a silver box about 2"x3" .
Is the furnace top hot?
Ok, lets go over what we have...
pilot is lit
thermostat is set for heat and turned up
furnace has power, but fan will not turn on by fan switch
motor has power to it.
Anything else you notice? Does the other furnace work?
Well, I think you are in the area of needing to troubleshoot with a meter.
Verify (with meter) 120 v into furnace.
Verify 24 v from transformer
verify blower motor operation
It sounds as though your blower motor is bad from the information you gave me.
I have verified 120 volts to the motor
I have 28 volts from the transformer
I expected the motor was the problem..Does that look like it? Is 28 volts from the transformer ok?
28 volts is great.
If you have 120 to the motor, and it is not running, you have a bad blower motor.
good luck, I am available for follow up.
Thanks for your help. I did not have the knowledge to confirm the problem, and you can spend a lot more on guesses than you save.
I am a mechanic, and so I know the value of a good tradesman.