Furnace Problem

[James Murphy]

Hi

I have a Lennox Wisper Heat Central Forced air natural gas furnace model # G20RQ3XE-75-1 with a problem

The problem is this

Turn on thermostat igniter clicks after a few seconds small flame appears igniter keeps clicking blower fan turns on blowing cold air

igniter keeps clicking for a few minutes with small flame present , large burners never turn on.

after a few minutes the igniter stops clicking and the small flame goes out.

is there a small primary burner what I am seeing and a larger secondary burner that never turns on? what would cause this.

I have a dvm and am handy, can perform tests and checks.

Thanks James

[Tony Hwang]

Hi, If flame is on, flame sensor should sense it for next sequence of event. Doesn't controller give trouble code by way of blinking LED light? Tony

[James Murphy]

Controller doesn't have a LED light.

Also, problem existed for a week then the furnace started to work again, now it doesn't work.

Thanks James

[Tony Hwang]

Hi, Flame sensor tends to get sluggish when surface rust builds up. Clean it with emery cloth of fine sand paper. Tony

[Stormin Mormon]

You getting 24v at the gas valve? Sounds like a bad solenoid on the gas valve. Of course, I'm not there to see.

Please remit $47.50 for advice.

[Stormin Mormon]

There may be a sensor in the pilot flame. The one I worked on this year had a bad flame sensor in a Bryant. It would flame up, and the main flame would go out after a second or two.

Not enough to heat the house.

Sears gets about $203812093801238.99 for them. I got one wholesale, and charged a good price for it.