Lennox pulse 21 installation manual - Heating & Cooling

Oddly, I can't even find the Y2018 model on the Lennox site nor on the entire internet. I looked at a 7500 comfortsense manual and no where in that manual is a battery mentioned. Some thermostats do indeed contain batteries to preserve settings.

The Lennox home site seems to direct people to Lennox dealers. If the manual for your thermostat does not include a support number other than warranty, you may have to talk to a dealer/installer. Sorry.

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NEW Champion Pulse Spark Plug Y99 FI21500 CH21500 Lennox 43G62 Replacement...

See if you blower speed is set to low speed in the heat mode.
I think what might be happening is the blower is set to low speed in heat and when you switch to automatic, the blower is switched to high speed. You may have to change the blower speed to high in the heat mode. If not you may have an airflow problem such as a Dirty filter, ducts not sized right, dampers on the room outlets closed.

Click the link below. It is in PDF format. http://www.hvacpartsshop.com/manuals/G21_Series.pdf

Have seen a rash of faulty blower time delays in lennox equipment. Lennox has a recall on one currently, not sure if your system is effected but it can be bypassed if in fact the problem.

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

Hi,
That can be a bad relay, but it also can be the high limit has tripped...or went bad...when the high limit thinks that the furnace is too hot the blower will run continuously...
The best way to troubleshoot is to unhook a wire from the high limit and see if the blower stops... if it does then the high limit is bad or needs to be reset...

if it continues to run then the relay is likely welded together...

heatman101

you will need to verify voltage from the board to the inducer. If you have the installtion manual there is a flow chart for the sequence of operation of the furnace.
The basic sequence is:
1. thermostat calls for heat
2. inducer motor starts and runs for a pre-set amount of time
3. the pressure switch closes and allows for ignition trial
4. ignition is proved back to the board allowing the system to operate.

Verify 120VAC to the inducer motor upon call for heat from stat, if you have 120 at the leads that connect to the inducer and it does not start , the motor is faulty. If the inducer starts use a voltmeter across the pressure switch terminals, a voltage reading of 0 VAC will verify contact closure and ignition should occur.

The pulse furnace was under a factory recall due to breaches in the heat exchanger, unfortunately for you, the Lennox Corp. has ended the program that allowed for an allowance / furnace for replacement. To test the heat exchanger a special kit is required from lennox that will verify integrity of the heat exchanger. (If the heat exchanger seal has been comrimised the pressure switch will not prove and the igniton sequence will be interupted and cause the system to go into "lock-out" mode).I know this is probably not what you wanted to hear. Hope this helps, please list as "very helpful" if it did

If this is a high eff model, check to make sure the intake vent is not plugged.

The bearings are bad. You need to replace the motor. Motor cost $75 to $125. Labor is on avg. $150 to $400 with an decent A/C Company . You can try to oil it but its not recommend by Lennox. That furnace at the time they build it was top of the line. Good Luck.