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Old 04-22-2012, 03:43 PM   #1
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Lennox furnace Problem


hi i have a lennox furnaceaG71MPP Series and I turned the heater on and heat does not come out cold air blows out but also a red light blinks with the letteres cal but never do nothing you hear it about to do something but never do has been doing this for 24 hrs house is cold what can be the problem furnace about 3yrs old help

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Last edited by beenthere; 04-22-2012 at 04:12 PM. Reason: Fixed all caps typimng.
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Old 04-22-2012, 03:51 PM   #2
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Quote:
Originally Posted by ms callie
hi i have a lennox furnaceaG71MPP SERIES AND I TURNED THE HEATER ON AND HEAT DOES NOT COME OUT COLD AIR BLOWS OUT BUT ALSO A RED LIGHT BLINKS WITH THE LETTERES CAL BUT NEVER DO NOTHING YOU HEAR IT ABOUT TO DO SOMETHING BUT NEVER DO HAS BEEN DOING THIS FOR 24 HRS HOUSE IS COLD WHAT CAN BE THE PROBLEM FURNACE ABOUT 3YRS OLD HELP
Perhaps your not aware of it but typing in all caps is considered shouting on the intenet.
Second,if you have a question about a problem you're having you should start your own thread about your problem not hijack another thread.

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Old 04-22-2012, 04:13 PM   #3
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Lennox furnace Problem


Perhaps Member Yuri will see this thread, he is well versed on Lennox furnaces.
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Old 04-22-2012, 04:25 PM   #4
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Lennox furnace Problem


Lennox's are awful machines..You listening Yuri?

Cal just means that your furnace is calibrating the high and low pressure switches. Depending on your thermostat, this can happen with every heating cycle.
Are you hearing the inducer motor running?
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Old 04-22-2012, 04:34 PM   #5
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Lennox furnace Problem


yes it is it just keep doing that seems like it wants to do something but dont,sorry about the capital letters im new to this and new to computers
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Old 04-22-2012, 04:37 PM   #6
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Lennox furnace Problem


is the small black motor in the top part of the furnace running....thats the first thing that needs to happen on a call for heat.... turn stat off then back on and watch what happens in the top part of the furnace with the top door off...
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Old 04-22-2012, 04:41 PM   #7
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it dont come on with top door off
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Old 04-22-2012, 05:15 PM   #8
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now you have to prove its calling for heat.... do you have a volt meter...
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Old 04-22-2012, 05:17 PM   #9
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The pressure switch is not closing. There's a tube that runs from the exaust inducer motor to a round disc looking thing, call ed a pressure switch. The inducer puts negative pressure through the tube and sucks closed the pressure switch, proving that the furnace can exhaust the burned gas fumes, allowing the furnace to light.

Carefully remove the tube and with the use of a straightened paper clip clear the ports it connects to, both on the inducer and on the pressure switch. Check that hose for any cracks or obstruction as well.

The funace isn't coming on because there's a door switch that isn't being pushed in with the door off. You can tape that switch in while the door is removed to allow power to the furnace.

Also, you can remove the tube ONLY from the inducer while leaving it on the pressure switch and with the furnace on call for heat, with the door switch taped down, you can suck on the tube thus closing the pressure switch and the furnace should light. If it does than we know that there's some kind of obstruction such as in those ports where the tube connects or possibly the flue pipe.

Very rarely does a pressure switch fail. An inducer motor can become weak and not pull enough air to close the pressure switch, though. You'd need a manometer to test that.

Some things to think about.
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Old 04-22-2012, 05:23 PM   #10
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Quote:
Originally Posted by sublime2 View Post
Perhaps your not aware of it but typing in all caps is considered shouting on the intenet.
Second,if you have a question about a problem you're having you should start your own thread about your problem not hijack another thread.

you typed in all caps, not the op. It was oversized and bold, but not all caps.
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Old 04-22-2012, 05:24 PM   #11
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get over it already!!
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Old 04-22-2012, 05:26 PM   #12
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get over it already!!
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Old 04-22-2012, 05:54 PM   #13
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Quote:
Originally Posted by Doc Holliday View Post
The pressure switch is not closing. There's a tube that runs from the exaust inducer motor to a round disc looking thing, call ed a pressure switch. The inducer puts negative pressure through the tube and sucks closed the pressure switch, proving that the furnace can exhaust the burned gas fumes, allowing the furnace to light.

Carefully remove the tube and with the use of a straightened paper clip clear the ports it connects to, both on the inducer and on the pressure switch. Check that hose for any cracks or obstruction as well.

The funace isn't coming on because there's a door switch that isn't being pushed in with the door off. You can tape that switch in while the door is removed to allow power to the furnace.

Also, you can remove the tube ONLY from the inducer while leaving it on the pressure switch and with the furnace on call for heat, with the door switch taped down, you can suck on the tube thus closing the pressure switch and the furnace should light. If it does than we know that there's some kind of obstruction such as in those ports where the tube connects or possibly the flue pipe.

Very rarely does a pressure switch fail. An inducer motor can become weak and not pull enough air to close the pressure switch, though. You'd need a manometer to test that.

Some things to think about.
the inducer motor is not running gotta get that going first before we worry about pressure switchs
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Old 04-22-2012, 05:59 PM   #14
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Quote:
Originally Posted by ms callie View Post
yes it is it just keep doing that seems like it wants to do something but dont,sorry about the capital letters im new to this and new to computers

Uhm, the furnace isn't running with the door off but she said that yes, the inducer is running (with the door on?). That's what I got from this and a previous response, at least.

?
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Old 04-22-2012, 06:33 PM   #15
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Quote:
Originally Posted by Missouri Bound

you typed in all caps, not the op. It was oversized and bold, but not all caps.
Thanks for that helpful input! Had u seen her OP you would realize how foolish you sound right now.

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Last edited by sublime2; 04-22-2012 at 06:42 PM.
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