Original message
| racer
 |  "Fan won't shut off on Lennox Pulse21"
, posted Thu 6 Jan 13:34  
I have a Lennox Pulse21 Model G21Q4-80-1 gas forced air furnace, 10 years old. Normally the fan shuts off about 3 minutes after the "burner" shuts off. Now, for about half of the heat cycles the fan continues to run non-stop after the "burner" shuts off; the other times the fan shuts off as normal. If I turn the power switch off and back on the fan stays off until the next heat cycle. I am thinking of replacing the part labeled Honeywell Limit Control L4064E2536.
Is there another part, such as a timer, that could be the problem?
The limit control has two wires connected.
Several supply companies I have called cannot find the exact limit control number L4064E2536; they have numbers such as L4064B2236.
Is an exact match on the part number important or is it OK to match the appearance and probe length of the limit control?
Would a Pulse furnace make a difference in the required limit control?
Thanks
|
|
Replies:
|
| zekeman
| "Re(3):Please help....freezing!!" , posted Thu 6 Jan 21:25
It could be a marginally low limit switch setting than the thermostat setting.
As a test, simply lower the thermostat setting by about 5 degrees to see if it operates normally. If not it may be the low limit switch failure. If that works then raise the low temp limit by 5 to 10 degrees.
|
| Xenos
Webmaster 
| "Re(1):Fan won't shut off on Lennox Pulse21" , posted Thu 6 Jan 19:49
When the fan is running non stop does the furnace still operate properly? if not what is the error code?
Xenos.
The best way to escape a problem is to solve it.
|
| | racer
| "Re(2):Fan won't shut off on Lennox Pulse21" , posted Sat 8 Jan 13:35:
I replaced the Fan/Limit Control with a similar model # Honeywell 5". It had only two wires connected to it on the limit side - no wires connected to the fan side. Does this mean the Fan/Limit Control is ONLY controlling the Limit for a safety shutdown of the burner if it gets to 200F and the Fan on/off is controlled somewhere else?
The installation manual says:
" Fan Timer Control
Fan On Delay Timing - Factory set at 45 seconds and adjustable from 30 to 60 seconds.
Fan Off Delay Timing - Factory set at 180 seconds and adjustable from 120 to 240 seconds."
But it does not say where the "Fan Timer Control" is or how to adjust it.
The wires from the thermostat connect to the furnace on the "Control Box" which has a door/panel with two screws. This "Control Box" is located at the bottom of the Access Panel. I am wondering if a "Fan Timer Control" is behind the wire terminals inside this "Control Box".
I do not know if replacing the Fan/Limit Control fixed the problem because the problem is intermittent. For example, 2 days of problem followed by 10 days running perfect, followed by 2 days of problem. So only time will tell if it is fixed or not but I keep wondering why there were only two wires on the Fan/Limit control instead of four wires and if the Fan on/off is controlled by something other than the Fan/Limit Control.
Can anybody help? Thanks.
p.s. Regarding questions asked, I will test if/when it next malfunctions. Thanks.
[this message was edited by racer on Sat 8 Jan 13:39] |
| | Apprentice
| "Re(2):Fan won't shut off on Lennox Pulse21" , posted Fri 7 Jan 08:53
When the unit burners cycle off and the fn continues to run non stop, tap on the fan/limit control. If it shuts right down then, the switch is sticking and should be replaced. You're on the right track.
Exact model of fan/limit isn't critical, but probe length should be the same size as original. If you have to, you can go longer with the probe but not shorter.
|
|
|
