Advice on diagnosing Rheem furnace problem

[oliverc]

I have a Rheem Criterion model RGDG-05NAUER, and I need help diagnosing the problem, which started after the thing had been running almost continuously for a few cold days.

When the thermostat calls for heat, the induction draft blower starts up and does its 30 second prepurge. The igniter doesn't glow. The gas comes on for a few seconds, but, of course, it doesn't light. After that, it just waits for a while and goes through the same cycle over and over again.

According to the troubleshooting flow diagram, this could be caused by a defective "Air Proving Switch" (or pressure switch, I guess it's more often called), a blocked vent, a faulty igniter or a control-board/ wiring problem. I'm pretty sure the vent is OK. I just don't know how to check the pressure switch. How do I know if it's working or not? (According to the manual, it's supposed to be closed if it's working OK. I tried shorting it out, but then not even the draft blower would come on.)

If it is the pressure switch, where can I find a replacement? I've looked all over the web, and I can't find any replacement for this part, which is:

Tridelta
FS6012A-1683
615917/1694/R (or maybe it's A)
42-24864-62

(The 6, 0 and 8 all look kind of the same, I can't be sure the number is right no matter how long I stare at the tiny printing!)

One last question, which probably isn't relevant to the problem but I'd like to know anyway: There's a limit switch on the hot side of the compartment. It's a small thing with a little red cylinder sticking up out of it. How do I know whether it's been triggered and needs to be reset? And how would I reset it if I had to? When I push down on it, there's no give -- it doesn't feel like it would go down no matter how hard I push.

I do have a multimeter, but it doesn't do continuity testing (yeah, I'm from the stone age).

Thanks for any help you can give me.

BTW, does anyone else find it really irritating that the manufacturer gives almost no help on this stuff? And that every service place in town (Los Angeles) refuses to sell parts? I mean, shouldn't a guy be allowed to try and fix his own furnace if he wants to?

[mike n]

It's not the switch or the gas valve wouldn't open you need to unplug the igniter and put two meter leads in the holes of the plug with the furnace off, set your meter to volts ac then turn the furnace on after purge you should get a voltage reading if you do the igniter is bad you should have a local rheem distributor but if you don't rheem or ruud either one can sell you the same part.

[oliverc]

Thank you, thank you! It was just as you said: igniter was bust. You are smarter than the manual. Two hours of blood sweat and tears later, fiddling in the innards with a hex wrench, I have heat!

[HayZee518]

next time you need a part check out this site. -
Shortys HVAC Supplies, "Short on Price, Long on Quality!" - Indianapolis, IN