Gas and Oil Home Heating Furnaces - Rheem Furnace gas valve clicks on/off crazy

Hi all.

this is a 1986 vintage Rheem gas furnace, model is
RGDD-06NC-ER

The ignition module is a Robertshaw SP715A

The gas valve is a Robertshaw 711 DER-SC

The problem: When heat is called for, often it works normally, but often the gas valve will click, the pilot comes on (electric spark ignition), and the burner will fire, then the gas valve starts clicking on and off, very fast, randomly (no cadence), and the unit will shut down.

Or, it starts clicking madly as soon as the pilot lights, and the burner will not fire. Or some variation of this, but always the gas valve is clicking madly.

I removed the flame sensor and cleaned it, but no difference. I also cleaned up the thermostat connections and contacts, no joy.

Is there a way to test the flame sensor?

Any other sensors that might be bad.

Any help diagnosing this problem is greatly appreciated.

I do have some electronic skills and diagnostic tools.

thanks

do you have a meter to see if for sure the t-stat isn't dropping out on you?

If you do have a meter, take a reading on R and W, and see if that power is steady. If turns out it's steady, then take a reading as the gas valve, and see if power is steady. if it's on and off as you said, then it's the control. But if the power is steady, then it's the gas valve itself.

I forgot to post a follow up on this issue back then when I tried your suggestions, Jay, so here it is.

I did as you suggested, the problem turned out to be the ignition control module. I opened it up, and just cleaned the relay contacts and replaced it. It's been fine since then.

thanks for your assistance, I really appreciate it.

Wow, almost a year later you came back.

Thanks for the update.

Yes Jay, I did forget! I am a die-hard DIY'er, and I seek out professional help on various forums whenever I think I need it. I usually try and figure things out myself, sometimes that works, sometimes it doesn't. In the case of a furnace, I felt it would be more prudent to ask questions first! :-)

Anyway, I just wanted to thank you again for your assistance. I had asked the same question on another forum, and got a response that inferred that I shouldn't be messing with my furnace, I may poison my family with CO, and I really should just call in a professional. Of course, that forum is mostly HVAC techs. A rich source of info, but unwilling to share it.

Your forum was 180° opposite. You were helpful from the get-go.

Thanks again for your help.



Dana