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Furnace won't start. I have a Lennox G61MPV Furnace with a Lennox Elite Series 3 Programmable Thermostat. We have noticed once in a while some "disconnect" in the past between what we have programmed and what the furnace actually does, but starting yesterday the furnace doesn't come on at all now. We have 75 people coming for an open house this evening and it's 35 degrees outside (60 inside.) Any ideas?
Sounds like a big day!...Can you tell me if a red light is visible through a small viewing port in the bottom door of the furnace?
See page 91 here -
This is the specific service manual for your unit. Page 91 starts the description of fault codes.
A constant pulse is normal as shown on page 33 here -
Do you mind removing the thermostat top section for a test?
Remove the top section to where we can see the thermostat wires and where they attach.
We want the wire on terminal R (could be RC,RH) that is commonly red, and the white wire on W (could be W1)....we want to twist those 2 together or touch them at same time with short wire or paper clip shaped in a U.
The goal is to connect the red wire to the white wire. This bypasses the thermostat and will tell us if we have a thermostat issue or furnace issue.
When red and white touched together the furnace should start.
Now reassemble thermostat, turn power off to furnace for 10 seconds, turn back on, thermostat back up.
Then tell me exactly what the sequence is including the flash code.
?? Not sure how to turn power off to furnace. I can turn thermostat to "off" (from "heat" or "auto"). Is that what you mean? Or do you mean flip off the breaker to the furnace? And does the "flash code" show up on the thermostat screen or the two little lights (one that's off, the other flashing green) I can view through furnace door?
Cut power to furnace via breaker or power switch on side of furnace.
The lights with fault codes will be visible through the small port in bottom door of furnace.
Tell me if any noise or operation happens with furnace also.
Flashing at same pulse or alternating?
There is a small exhaust fan in the upper section that usually starts first. Does the motor feel cool or hot?
Ok we are going to try something....
In the top section is a pressure switch. It has rubber tubing going to it that air is pulled through to activate a switch. It also has a couple of wires to it.
See page 23 if you need location. http://www.cozyparts.com/Lennox-Parts/forum/Lennox_service_manual/Furnaces/G61MPV_09-01-2007.pdf
Tap on those switches, remove the rubber tubes and make sure the tubes and ends are clear. I am hoping one of these switches just got stuck closed. Reassemble and try furnace.
The concern I had is with the red and white wire jumped. The very first thing to happen is the circuit board evaluates various inputs, and then starts the exhaust motor. Possibly the click you hear is the relay telling it to run.
The motor may not start because it is bad, stuck at a "dead spot" in the motor or a object/rodent/bird has made its way to housing and has the motor stuck.
The goal now is turn off power and find a way to see if the motor assembly can turn freely.
Page 23 - combustion air inducer. http://www.cozyparts.com/Lennox-Parts/forum/Lennox_service_manual/Furnaces/G61MPV_09-01-2007.pdf
It is the motor assembly that the plastic pipe attaches to.
Ok, that is our stumbling block. The motor is either bad or stuck. Unfortunately I am in a hands off situation where I can only go so far. The rest would require using a meter to ensure 120v to motor and that it is not stuck.....
I apologize, but that is where we are at.
Lennox dealer will be able to tell depending on motor in stock. So call a Lennox dealer for service.
Bad news...could be $400-$500 bucks total. If it is a bad motor. It comes as the entire motor, housing, wheel etc.
OK, thank you. . .