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.