Help with Lennox furnace

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Old 09-24-07, 10:24 AM
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Help with Lennox furnace

I have a Lennox furnace/AC that has worked fine for 7 years but this weekend the batteries went dead in my Honeywell/35thermostat and now nothing works. I have changed those batteris other times with no problem but I don't think they ever died before.

The thermostat appears to be working, all of the information such as time, setpoints, etc. appear normal and it seems to click when I change the setpoint above the room temp. But neither the furnace or the AC work. I cannot even turn on the fan manually from the stat.

Everything worked fine until those batteries died so the prob must be with that thermostat but I am at a loss as to what it might be.
The Lennox furnace has neither of those diag lites on. I have never seen both of them off before. When I push in the interlock (with the panel off) I hear a hum so I am guessing the power is there.

Any help would be appreciated.............
 
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Old 09-24-07, 05:47 PM
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Originally Posted by zepherz View Post
I have a Lennox furnace/AC that has worked fine for 7 years but this weekend the batteries went dead in my Honeywell/35thermostat and now nothing works. I have changed those batteris other times with no problem but I don't think they ever died before.

The thermostat appears to be working, all of the information such as time, setpoints, etc. appear normal and it seems to click when I change the setpoint above the room temp. But neither the furnace or the AC work. I cannot even turn on the fan manually from the stat.

Everything worked fine until those batteries died so the prob must be with that thermostat but I am at a loss as to what it might be.
The Lennox furnace has neither of those diag lites on. I have never seen both of them off before. When I push in the interlock (with the panel off) I hear a hum so I am guessing the power is there.

Any help would be appreciated.............

when you took the thermostat off to replace the batteries, any chance that a wire at the thermostat came loose or broke off? look at the wiring teminals at the thermostat, you should see terminals R,G,Y,W. try a jumper wire from R to G it should start the inddor fan, a jumper from R to W should start the heating cycle
 
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Old 09-24-07, 06:50 PM
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Wink

Some furnace units have a small fuse on the board In them . Have you checked that out?????
 
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Old 09-28-07, 09:29 AM
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Originally Posted by daddyjohn View Post
when you took the thermostat off to replace the batteries, any chance that a wire at the thermostat came loose or broke off? look at the wiring teminals at the thermostat, you should see terminals R,G,Y,W. try a jumper wire from R to G it should start the inddor fan, a jumper from R to W should start the heating cycle
Thanks for the responses to my request for help.

The theromstat checked out okay. I had a service call from the vendor who installed the furnace/AC and he checked out the thermostat.
I think the batteries getting low was a red herring. My wife had noticed the A/C has stopped working before she changed the batteries and that is why she noticed the low battery inidcation and changed them.

Turns out there is a small 24V breaker inside the furnace enclosure on a PC board that was tripped. He reset it and the furnace started. (only $89.95 for that service)
He did not however fully check the unit because had he done so he would have found that the A/C trips the breaker and not the furnace. So I have another call into them for another look at it. Hope it don't cost me another $89.95 for the second look! Being an A/C unit it may very well be a lot more then that though.

Any idea why the A/C trips the common 24V thermostat breaker? As long as the furnace is working the breaker does not trip but as soon as the A/C is selected at the thermostat the breaker trips.


Thanks..............
 
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Old 09-28-07, 11:58 AM
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Originally Posted by zepherz View Post
Thanks for the responses to my request for help.

The theromstat checked out okay. I had a service call from the vendor who installed the furnace/AC and he checked out the thermostat.
I think the batteries getting low was a red herring. My wife had noticed the A/C has stopped working before she changed the batteries and that is why she noticed the low battery inidcation and changed them.

Turns out there is a small 24V breaker inside the furnace enclosure on a PC board that was tripped. He reset it and the furnace started. (only $89.95 for that service)
He did not however fully check the unit because had he done so he would have found that the A/C trips the breaker and not the furnace. So I have another call into them for another look at it. Hope it don't cost me another $89.95 for the second look! Being an A/C unit it may very well be a lot more then that though.

Any idea why the A/C trips the common 24V thermostat breaker? As long as the furnace is working the breaker does not trip but as soon as the A/C is selected at the thermostat the breaker trips.


Thanks..............
It's probably an issue with the control wiring going to the outdoor unit or a component inside the outdoor unit that has failed [for example- the contactor]. Take a look at the wires at the outdoor unit, you should see a small cable. Maybe it was hit by a weed wacker or a critter chewed it? The technician should have verified that all parts of your system were working. Circuit breakers don't normally trip for no reason
 
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Old 10-01-07, 11:19 AM
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Originally Posted by daddyjohn View Post
It's probably an issue with the control wiring going to the outdoor unit or a component inside the outdoor unit that has failed [for example- the contactor]. Take a look at the wires at the outdoor unit, you should see a small cable. Maybe it was hit by a weed wacker or a critter chewed it? The technician should have verified that all parts of your system were working. Circuit breakers don't normally trip for no reason
Bingo! You hit the nail on the head. The tech came and found a shorted wire on the outside unit. I think I remember slightly moving that unit when I was painting the house so that little shove probably cost me a total of $315.00 dollars to get repaired.

On the bright side he said that the PC board costs $900.00 to have replaced and the compressor costs $1500.00! Maybe he was just trying to make me feel better about paying $315.00 to replace a wire. Boy I must have been in the wrong business all of my life!

Thanks for the responses............
 
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