Furnace blower fan not starting...

ÜberFly · #1 08-09-2020, 01:55 PM

Gang,

Looking for some advice before having to make a service call...

Just finished painting our upstairs... Removed the thermostat (simple programmable - so just popped off the control panel to cut around). Since replacing, furnace blower fan will not turn on (we normally have it run continuously) - have fan on, on the control panel... Tried resetting the power on the breaker panel. Fan does comes on when I turn up the thermostat, but blower isn't running beyond that... Also, main furnace fan override switch is on... Was running fine prior to removing the thermostat control panel...

Looked to see if there is a reset switch under the cover, cannot find one.

Carrier mid-efficiency furnace about 13 years old.

Anyone have any insight?

Thanks in advance.

Peter

calgarychef · #2 08-09-2020, 02:10 PM

You need to ask Caber tosser... he’ll give you the straight goods.

HyperMOA · #3 08-09-2020, 02:13 PM

If the blower functions when the heater is engaged I would say your furnace is working correctly. So it’s either the thermostat has failed and the “fan on” function isn’t working or any control between the furnace and thermostat. Such as a relay or something. I’d take the thermostat off again and check that all the connectors are clean and making contact.

CaberTosser · #4 08-09-2020, 02:23 PM

If you pulled the thermostat away from the wall for the painting, its possible that the green wire for the G terminal got either disconnected, or even broken. I've had lots of calls from broken thermostat wires ( such as when you work-harden a piece of copper or steel by bending it back and forth, and finally it yields and breaks).

MyAlberta · #5 08-09-2020, 02:28 PM

Or pin on back of thermostat was bent

CaberTosser · #6 08-09-2020, 03:15 PM

I once had a call just about two blocks away from UberFly in a house that was converted to a Dr's office, there was an intermittent issue with the furnace not firing. The house was perhaps 1930's or 1940's but had a 1970's furnace. I went over the furnace with a fine toothed comb and it would always respond perfectly. I wound up changing the thermostat, figuring it was the intermittent part because the furnace operated perfectly when I tested it with the thermostat wire detached. I got a call-back and checked both again, and then I clued in to something subtle: the thermostat wire in behind the thermostat was old cloth-covered wire, but all the thermostat wire downstairs was more modern plastic-jacketed wire. There was obviously a splice hidden in the wall, and on what was only 12' of wire in the first place... I taped some new stat wire to the existing wire and pulled it through, the 'splice' consisted of each conductor twisted into a lasso and the other conductor run through that and twisted back around itself. The loop was loose and didn't even have electrical tape on it... It would be easy enough for the loops to float without actually contacting each other, or as was the case, to have some contact, but be it from vibration or thermal expansion, to intermittently break contact.

ÜberFly · #7 08-09-2020, 04:20 PM

Pins are good...

Wires are intact...

artie · #8 08-09-2020, 04:38 PM

my thermostat takes a AAA battery which I try to change a couple of times a year
if a buddy has a spare thermostat you can try to see if yours is still good

ÜberFly · #9 08-09-2020, 04:40 PM

Good idea, I'll swap out the one from downstairs and see if that works!!!

Quote:

Originally Posted by artie

my thermostat takes a AAA battery which I try to change a couple of times a year
if a buddy has a spare thermostat you can try to see if yours is still good

ÜberFly · #10 08-09-2020, 04:42 PM

Yup!! It works! Must be the thermostat...

Quote:

Originally Posted by artie

my thermostat takes a AAA battery which I try to change a couple of times a year
if a buddy has a spare thermostat you can try to see if yours is still good

nimrod · #11 08-09-2020, 08:29 PM

You are so lucky, that it is not -30 right now, hope you find whats up.

huntwat · #12 08-09-2020, 09:24 PM

Quote:

Originally Posted by nimrod

You are so lucky, that it is not -30 right now, hope you find whats up.

His furnace works fine. Just the fan doesn’t constantly run when switching on at the t stat.

MyAlberta · #13 08-09-2020, 10:16 PM

2 thermostats must mean two furnaces. That saved me a couple of times

ÜberFly · #14 08-10-2020, 08:37 AM

So I pulled the panel and put back on a couple of times... I noticed that the fan would start up for a few seconds and then stop... Did it a few more times and it started to stay on...

So, I guess I'll let it run for now and then if and when, I'll purchase a new one...

Thanks for all responses and insight.

Cheers,

Peter

CptnBlues63 · #15 08-10-2020, 09:06 AM

Quote:

Originally Posted by nimrod

You are so lucky, that it is not -30 right now, hope you find whats up.

Came home one fine winter's day to discover the fan on my furnace quit turning. The motor was dead. Luckily my neighbor at the time (he moved some years back) did HVAC and had a pile of spare parts kicking around....including the exact electric motor I needed for the squirrel cage fan!

It was only -20 so not as bad as it could have been and I think the motor went an hour or so before I got home as the house was cool, but not cold.

Some times you get lucky!