040307 1638 - Ed posted:

Hi all, I'm a newbie at troubleshooting furnace problems, so please bear
with me........

I've got a home gas furnace that's failing to consistently turn on when it
is supposed to. Here's what I've done so far:
1) Checked circuit breaker for Furnace - OK
2) Reset the furnace by following the instructions inside the furnace to
turn it off & on - Done
3) Checked thermostat - OK. Removed thermostat and manually jumped the two
wires to make sure that furnace is turned on. Nothing happens to the
furnace.
4) If I hit the exhaust(??) blower - not the main blower that blows warm
air through the house, but the one by the flue pipe - the blower will start
to spin and in turn lights up the igniter. I'm not sure how this blower has
anything to do with the electronic ignition system, but this blower unit
must work before the igniter lights up. I should also note that this blower
unit has been squealing over the last while when it first starts up but I
didn't think much of it.
5) Once I get the unit up and running by tapping the blower, it may
continue to work fine for another half a day or so.
6) When it stops working, I have to repeat step 4 again. Seems like its
going to fail for good soon.

I hope this makes sense. Can anybody please tell me what the problem might
be?? and what can I do to fix it?

Thanks,

Ed



The furnace purge motor has to be operating before the main gas valve will
operate. There is usually a paddle in the air flow of this purge system to
let the system know that there is air flow and gases are being exhausted out
so that a gas flame doesn't ignite leftover gases and explode.

It sounds like this purge motor is lacking lubrication in its bearings, or
the fan blade is rubbing against something. If you want to work on this
yourself, you can remove the purge fan motor and fan and spin the motor
shaft and see if the bearings are OK. Check for sloppiness in the shaft
rotation. Connect the motor to its appropriate voltage and see if it
operates properly. If you need a new motor, you can contact your local
furnace company and give them the model of the furnace, and the model of the
motor and get a new one.