No spark-Lennox gas furnace

[irregularjoe]

Hi. First time poster.
My Lennox gas furnace will not light. I checked the relays, bypassed limit switches. Stat is ok. I hear the gas valve click when I set the stat to heat. Can't get spark at the ignitor. I checked all wires, and are ok.
Would this be a ignitor controller problem? Or gas valve?
Here are the specs:
Furnace- Lennox
model# G1603/4-100-1

Ignitor controller panel- Robertshaw
model# SP735L-Lennox P/N 1869101

Gas valve-
Robertshaw Grayson
7100 der?S7C
71F-11A-017

Thanks, Joe

[irregularjoe]

anyone? it's getting cold.

[Hube]

Have you tried cleaning the terminals (contacts) of the ignitor/ or gas valve wires?. Sometimes they get corroded, etc. Hube

[irregularjoe]

all the wires and contacts are good.

[Hube]

Then it must be a fault in the gas valve or ignitor. Check resistance (millivolt? or 24 V..? Hube

[irregularjoe]

yeah, I assumed that. I'm trying to determine which. Ignitor or valve. I really don't want to buy both.

[irregularjoe]

check resistance of what?

[irregularjoe]

OK. Latest results. I DID have some rust on one of the valve terminals that I did not see previously. Cleaned it, still NG.
I have 24 VDC going to the main ignitor control, but nothing coming out. What triggers the conrtoller to send 24 volts to the gas valve? I jumpered it out and the gas valve does open.

[irregularjoe]

I can apply 24 volts directly to the gas valve and can get both the pilot and main ports to open. (or at least I hear them clicking)
No ignitor though.
I'm assuming that the ignitor controller is the culprit.
Any thoughts would be appreciated.

[irregularjoe]

anyone know if robertshaw SP735L-Lennox igtion controller is available? can't find it online.

[irregularjoe]

Well I have heat again after 10 days without it.
I found a complete ignition kit at Graingers for $150. Ignition control panel, gas valve , and ignitor. It's a Robertshaw package (P/N 712017) and replaces the SP735. (which is obsolete).
It took 8 hours to install, as it was a different wiring configuration and nothing really fit correctly without some modification. Trying to install the damn ignitor was the worst part. But we have heat now. Personally, I could have got through the "winter" without it (78 degrees today) but my S.O. sure is happy!

Did you ever see OHM'S mother in LAW?...... SHOCKING!

[Troy]

I hate noone here was much help, you've been helpful to so many!

[irregularjoe]

quote:Originally posted by Troy

I hate noone here was much help, you've been helpful to so many!

Thanks, Troy.
I knew it had to be either the control panel (99% sure) or the gas valve. I just didn't want to buy one and then find out it was the other. So when I found Grainger's kit complete with the above mentioned two items PLUS the ignitor for LESS than the price of just the control panel at all the supply houses, I figured it was a no brainer. Don't know why I didn't consider them sooner, as there's a branch right here in town and I bought things from them years ago.
But..........On to the next crisis, I guess.

Did you ever see OHM'S mother in LAW?...... SHOCKING!