Gas and Oil Home Heating Furnaces - No Heat, but pilot works (lennox) - NOVICE

Hello,

I have to first warn you that I am an extreme novice to HVAC, but am generally pretty handy (don't have problem replacing a breaker box, brakes on my car or minor body work).

That being said, I have no heat (and it's cooold!). The fan runs fine, so I took off the top access panel to my Lennox G26Q4/5-100-2 furnace/blower unit. After I turn the shutoff switch on, about 20 seconds later the pilot lights (I can see it through the looking glass on the front of the metal box thingy). It stays on for about 15 seconds then shuts off for 30. Then it repeats this process over...and over...and over...but no heat ever comes out!!!

Sorry, I tried searching and poking around the forums, but I have no idea where to look or what I'm looking for.

Some details:
1. It is a natural gas/forced air unit. It has a White-Rodgers 36E gas regulator type thingy.

Can somebody help point me in the right direction?

Thanks a million!

--mobrien118

OK,

So I left the unit off for a little while, then I went down and took off the metal box thingy. Inside, I see the pilot light, so I remove it. In the process of doing this, I notice that the electrical connector to the "sensor" wire is loose, so I squeeze the female connector with a pliers and now it is solid. I believe it was making a connection, anyway.

So, now the pilot/ignitor flame (correct name?) stays lit. But the BIG FIRE won't come on!

Any help from here? Thanks in advance!

--mobrien118

P.S. One good thing that has come out of this problem is that I found this forum :-D

OK!

So I wiggled sone wires and found a few that weren't a tight fit. I may have actually loosened one of them while I was trying to find loose ones earlier! I think that this blue one that goes from the control box thingy to a round thingy on the back wall of the access box thingy, to another round thingy on the side of the box where the BIG FIRE comes from was loose.

Anyway, it fired up no problem.

Another concern I have, though, is that the blower comes on, then 30 seconds later the fire comes on. I thought it was supposed to be the other way around. Maybe something is wired backwards?

Thanks for providing a forum for me to bounce my thoughts off of (which is a real help, even thought I fixed it before anyone got a chance to respond).

--mobrien118

The blower that blows air out your house registers comes on first 30 seconds in advance of the fire?

The blower that blows air out your house registers comes on first 30 seconds in advance of the fire?

Indeed. And I thought the furnace was supposed to fire up first. I wonder which one shuts off first.

--mobrien118

So, now the pilot/ignitor flame (correct name?) stays lit. But the BIG FIRE won't come on!
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I have the same problem and I am prepare to have nightmares over the cost to get a pro in to fix it

I have the same problem and I am prepare to have nightmares over the cost to get a pro in to fix it

Yes, I was having nightmares, too. It seems like there are some pretty well qualified people on this site to help. I guess it just depends on how patient (or how cold) you are.

I guess a good place to start is by checking the wiring connections. I had to call out a repair guy over the summer and he opened up the bottom panel, saw that the wire to the cutoff switch (that tells when the door is open) was corroded, put a new connector on the wire and gave me a bill for $173. That's why I decided to try it myself this time. Turns out that this time it was wiring as well.

Good luck,

--mobrien118

I had to reread your OP. Sounds like your pilot flame is not being acknowledged by your control board. Could be a flame sensor if you have one into the pilot flame. Maybe even the board itself. Or maybe you have a pilot set up with your furnace where the shell of the whole pilot assembly has some electrical running through it and must be acknowledged by the board, before it decides to send a signal to the main gas valve to open. Or a thermostat acting up. Or ?.

The fan may be coming on simply within it's sequencing instruction based on time lapse. Your main issue of concern at the moment though is why the main gas valve is not receiving signal, or not opening.

Does your pilot have a flame sensor next to it? If you have one, you'd notice one thinner electrical wire going into the burner area next to the pilot. The wire would go into a mounting plate that usually has one screw. Then back behind where you might be able to see any more is a probe that the pilot flame touches. Often these need to be brightened up with something like fine steel wool, or scotch brite pad or equivalent. All you do is remove that screw and remove it.

Does the fan come on after the pilot comes on? Or does it come on even before the pilot?

See if you can check this out: Open your your furnace. Not the blower door. The main door where the gas valve is. And watch and see and listen. Place your finger tips on the gas valve and also listen. After the pilot comes on, see if you can feel or hear a click in the gas valve.