[josihair]

I have a Janitrol Heater/AC Model GU075-3 Serial Number 870707668
When I switch the Thermostat to Auto and Heat mode the Flame in the heater ignites and about 30 to 45 sec later goes out, The blower fan never comes on. However if I switch the Thermostat from Fan Auto to Fan on The Heater Flame ignites and the Blower comes on immediately. The Heater runs until reaching the selected Thermostat range and flame goes off and blower stays on. What could be the problem??
The Heater worked just fine last season, During the Summer the Blower motor went out and was replaced.

[hvac1000]

Sounds like you have a defective fan and limit control OR someone wired the motor incorrectly when it was replaced.

[josihair]

Sounds like you have a defective fan and limit control OR someone wired the motor incorrectly when it was replaced.

The blower motor was replaced this summer
When in Cool and Auto mode worked just fine
Does the Fan and limit control only work in Heat Mode??
I watched the cycle this morning when in Auto and Heat mode
When switched to Auto Mode, the Flame lites and I watch the wheel rotate through 140 and hear a audble click but blower does not start, when the wheel continues higher and reaches 170 the flame shuts off...

[hvac1000]

Does the Fan and limit control only work in Heat Mode

Yes. When it clicks the first time the blower motor should work in the heat mode. The second click is when it locks off the burner from overheating. This is the safety part of the control.Since the motor was replaced it could have been miswired and that could show up in the heat mode now since you want heat.

It is also possible the fan and limit control is defective. You will need to test the fan and limit and if it is OK I suspect the wiring. There should be a wiring diagram on the back side of the blower door that you can use to track down the problem.

If you do not know what you are doing and since this is a safety device I suggest you contact a local HVAC professional and have them do a ON SITE inspection and repair. You do not want to miswire the fan control if it needs to be replaced. A serious hazzard will exist if the wiring is not done correctly since this is a safety device.

[josihair]

Does the Fan and limit control only work in Heat Mode

Yes. when it clicks the first time the blower motor should work in the heat mode. The second click is when it locks off the burner from overheating. This is the safety part of the control.Since the motor was replaced it could have been miswired and that could show up in the heat mode now since you want heat.

It is also possible the fan and limit control is defective. You will need to test the fan and limit and if it is OK I suspect the wiring. There should be a wiring diagram on the back side of the blower door that you can use to track down the problem.

If you do not know what you are doing and since this is a safety device I suggest you contact a local HVAC professional and have them do a ON SITE inspection and repair. You do not want to miswire the fan control if it needs to be replaced. A serious hazzard will exist if the wiring is not done correctly since this is a safety device.

Went back and looked at the wiring
The Blower Motor was a replacement motor the factory original is no longer made...
The wiring on the old motor had wiring for LO /Med Lo /Med Hi and HI
The new motor had only wiring for LO / Med Hi and Hi
I hooked up red = LO Black = Hi and Blue = Med Hi and capped Orange which did not have a coresponding wire to hook up to motor

Today I moved the Red on the Motor to the Orange on the Furnace and the fan now works... Only thing I can figure is the voltage was too low for the fan to turn on the Low input but works fine on the next input up...

[hvac1000]

Glad you got it fixed