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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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My lennox lf24-60a-2 garage heater won't ignite. I put a new

Customer Question

My lennox lf24-60a-2 garage heater won't ignite. I put a new ignition electrode in and a new pressure switch. Turns on for 1 min then shuts off. Green light blinks 3 times over and over meaning pressure switch is is open or closed so that's why I put a new switch in. Didn't fix problem
Submitted: 1 year ago.
Category: HVAC
Expert:  Tim H. replied 1 year ago.

Hi, I'm Tim and I'm an HVAC expert here to help answer your question(s). Please provide all the information I ask for since I'm not onsite. At the end of our dialog you will be asked to rate my service, but please wait until then and all your question(s) have been answered satisfactorily. Thanks for your business!

Is the inducer motor running when you call for heat?

Customer: replied 1 year ago.
it is.
Expert:  Tim H. replied 1 year ago.

Get yourself a voltmeter and set to "volts AC" Put one probe on each side of the pressure switch terminal (on the metal portion). You should read 24 volts. Have someone turn on heat. As inducer comes up to speed, it should read "0" volts and stay there. Let me know what you find.

Customer: replied 1 year ago.
Do I tested the switch and it reads 0 when unit is not calling for heat and when I turn the thermostat to call for heat it goes up to 24
Customer: replied 1 year ago.
I tested not "do I tested"
Expert:  Tim H. replied 1 year ago.

Then it is stuck closed for some reason because the only time it should read "0" is when the switch is closed.

Customer: replied 1 year ago.
I just put a brand new switch in the other day. Do i have to replace where the switch plugs into below circuit board
Expert:  Tim H. replied 1 year ago.

Two things: the switch should not read "0" volts with no call for heat, it is a NO (normally open) switch. Secondly, I would check the other end of the pressure switch hose (not the pressure switch end) to see if that barb is partially plugged. Maybe run a small drill bit inside the barb.

Customer: replied 1 year ago.
Barb end is clean. Hose is clean.
Expert:  Tim H. replied 1 year ago.

If the readings you are giving me are right. sounds like the pressure switch is sticking closed with unit off, which will cause that flash code.

Customer: replied 1 year ago.
Ok so there are 2 black plugs that are mounted on the heat shield (that's what I figure it is) one is at the top and the second is at the bottom. Bottom one is direct connected to the pressure switch and the other to circuit board which leads back to the pressure switch with a different wire. Are those part of the pressure switch?
Expert:  Tim H. replied 1 year ago.

Can you upload a picture here of what you are talking about?

Customer: replied 1 year ago.
Not sure if you got pictures?
Expert:  Tim H. replied 1 year ago.

I can see part of the pressure switch, yes.

Customer: replied 1 year ago.
Top left corner is what I'm talking about. The is one at the bottom directly below connect to the as well
Expert:  Tim H. replied 1 year ago.

Looks like a bi metal disk. Possibly a heat sensor or fan switch.

Expert:  Tim H. replied 1 year ago.

Not part of the pressure switch, tough.

Expert:  Tim H. replied 1 year ago.

though

Customer: replied 1 year ago.
The pressure switch is connected to that though. Being that it is brand new switch what is the next step
Expert:  Tim H. replied 1 year ago.

Tap on the switch, maybe you'll break it loose. But it should not read "0" volts in the heat off position.

Customer: replied 1 year ago.
I can hear it close and open inside the switch
Expert:  Tim H. replied 1 year ago.

The reason you are getting the flash code and heat won't start is because the board "checks" the switch before starting. If it finds it closed, the heat won't work and you'll get the flash code.

Customer: replied 1 year ago.
I tapped on the switch nothing. I took the hose of the barbed end and plugged it back in to the barb and I could here the switch open and close when I did this
Expert:  Tim H. replied 1 year ago.

If it's closed with unit off, it's a bad switch. Sorry, wish it were something else.

Customer: replied 1 year ago.
How can I tell if it's a bad switch?
Expert:  Tim H. replied 1 year ago.

We just did. You confirmed "0" volts with no call for heat.

Customer: replied 1 year ago.
Ok so I just tested the switch again touching both sides of the switch with the meter and I get 0 reading when it calls for heat and 0 reading when it doesn't call for heat
Expert:  Tim H. replied 1 year ago.

You have to set meter for volts AC and touch both terminals of the switch AT THE SAME TIME. Should read 24 volts with unit off, and as inducer comes up to speed, "0" volts.

Customer: replied 1 year ago.
I have the meter set at 200v ac touched the switch both terminals still comes up as 0 for no call of heat and 0 for call of heat
Expert:  Tim H. replied 1 year ago.

Make sure you are making contact with the metal part of the terminals. Test the meter first in a home outlet, should read 120 volts.

Customer: replied 1 year ago.
I stuck the probes right through the hole in the terminals good contact there. As for
Expert:  Tim H. replied 1 year ago.

Based on the information you gave me, with a reading of "0" volts with unit off, this would lead me to believe the switch is bad. Try taking one lead off the switch, call for heat, and as soon as the inducer comes up to full speed, immediately push that lead back on the pressure switch. See if it runs and doesn't give you that flash code.

Customer: replied 1 year ago.
I tried that. Still getting the same code
Expert:  Tim H. replied 1 year ago.

Then you have a bad board.