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I have a Lennox lf24-150 that is giving me a 4 flash. It…

Hi I have a...

Hi I have a Lennox lf24-150 that is giving me a 4 flash. It runs perfectly for 2-3 cycles then starts fires but the fan doesn’t turn on. Then I get the 4 flash since it is overheating without the fan blowing.

Contractor's Assistant: I'll do all I can to help. How long have you been dealing with this?

A few days now

Contractor's Assistant: Do you plan on doing the work yourself?

Yes

Contractor's Assistant: Anything else we should know to help you best?

It’s 1 of 45 heaters I have so I’m use to working on these. It has 120v to the board all connections are good

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Answered in 32 minutes by:
1/17/2018
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,366
Experience: Furnace, A/C and heat pump specialist.
Verified

Are we getting 120v to the fan when it should be on but fan is just not coming on or is board not sending power to fan?

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Customer reply replied 7 months ago
No power to the fan at that point but the first few cycle it all works perfectly

BUt pressure switch is not opening or a limit until the fan actually causes limit to open due to not coming on?

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Customer reply replied 7 months ago
I think the limit switch is opening since the fan isn’t coming on. But I don’t know why the fan doesn’t come on after it had been working fine the fan moves freely

Has to be a failing ignition control board. Erratic behaviour is characteristic of a board going out. THere are no other components in the sequence after burners come on and prove flame that would keep fan from coming on. Can you steal a board from one of the other heaters to try ?

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Customer reply replied 7 months ago
that was my next step but I just wanted a second opinion I’ve had the boards go bad before on other heaters but they were just dead.
Customer reply replied 7 months ago
That’s great info I couldn’t find that anywhere I figured it was on a timer thank you I’ll switch the board out in the morning

I will upload you a manual if you don't have one

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Customer reply replied 7 months ago
That would be great thanks
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Customer reply replied 7 months ago
I got it thanks

If you have further questions, please let me know.
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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,366
Experience: Furnace, A/C and heat pump specialist.
Verified
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