Furnace blower runs continuously

[Voicer]

There is a separate switch to turn the furnace fan on to circulate air when needed. When turned off, the thermostat does not function. When turned on and the thermostat turned up, the burner ignites and the fan increases in speed. Turning the 'fan off' on the thermostat reduces the fan to a lower speed but the only way to turn it off completely is by the main switch. Is it normal for the fan the run constantly like this? If not, how do I control it from the thermostat?

[16x80]

Voicer

Welcome to the Home Repair Forums

No its not normal, You have a bad fan relay (on older furnaces) or a bad control module (on newer furnaces)!

Help me out what brand Model# would help also, How old would be very helpful!

16x80

[Voicer]

Thanks for the quick reply. It's a Clare Brothers Furnace,(Canadian) Model LBG 102 and approx. 20 + years old but motor and other parts have been replaced but not sure about the fan relay. Is there an easy way to troubleshoot the relay?

[16x80]

Its a voltage issue, You will need a volt meter. You will find that power is being supplied to the fan motor. Usually cause by a sticky relay or burnt relay that is causing bleed over of the power to the motor

16x80