Heil DC90, no heat

GoneFission · 10-18-2011, 11:15 AM

I have a Heil DC90 in the attic of my garage, that is not working. The draft inducer fan comes one, the vacuum switches all trip, the HSI glows, but the main burner never comes on. The HSI just keeps glowing. Most times, I can see a small "pop" of a gas flame hear the pilot assembly, but it is impossible to view the pilot flame through the sight window.

I removed the pilot assembly, and carefully cleaned the flame rod with some scotchbrite, but I have not reinstalled the pilot assembly yet.

Just looking for some ideas on what to check next, if this doesn't work.

Is it OK to hook up the pilot assembly to the gas valve, outside of the burner box, to check the flame operation?

hvactech126 · 10-18-2011, 05:56 PM

It is not ok to assemble the pilot outside of the burner box. You should remove the pilot orifice and clean it if at all possible. DO you have a honeywell SMARTVALVE gas valve? sounds like you do. try wiggling the wire to the valve. Those things are notorious for going bad.

GoneFission · 10-18-2011, 06:56 PM

Thanks! It is a Honeywell Smartvalve.

I put it back together, and turned it back on. it still goes to the same point, where the HSI never turns off, and the main gas valve doesn't open.

It looks like the pilot is getting a decent flame. I'm getting about a 70 millivolt signal back from the flame rod, wheneveer the pilot is on, so I think that my pilot and flame rod are working properly.

I'll try wiggling the wires, even though I've done about 20 "break and make" cycles with that connector already, while I was working on the pilot assembly.

Otherwise, would it be a bad Smartvalve? The furnace is about 14 years old

hvactech126 · 10-18-2011, 09:23 PM

there is a high probability that the valve is bad. Flame signals are measured in micro amps DC not millivolts.

GoneFission · 10-19-2011, 07:29 AM

I'll see if my Fluke has a setting for DC micro amps.