Furnace Problem

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
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James Murphy wrote:

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
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#
large
out.
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

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James Murphy wrote:

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