Burnt Air Furnace

John Fernandez_2

Befor you guys start throwing rocks.......... I have a question regarding a forced air gas furnace (there I said it ). The furnace is equipped with a Honeywell electronic ignition type gas valve and a Honeywell electronic ignition module ( I can get the mfgr's numbers if needed). Problem is this......t-stat calls for heat, vent blower comes on, pilot lights, burner comes on, runs for appr 30 seconds then burner goes out. Burner will go on and off until t-stat is shut down. Yes after a period of time, this on/off cycling will eventually warm the plenum and start the fan via the fan-limit switch. Any help will be appreciated.

Robert O'Connor_7

Sorched Air .....shame-shame

I have more questions than answers but I'll bite. Check the limits and or the tfe's...Robert O'Connor/NJ

Unknown

Check the

microamps when it is running and see if they drop off just as it goes out. If it does it may need a gas/air adjustment. It is also a good idea to clean the pilot and clean the flame rod (use a soft clean emory cloth). Is this using a Honeywell pilot? If you are not familar with how to take microamps let me know and I will walk you through the procedure.

What is the number on the module?

How long has this been going on?

John Fernandez_2

Here are some.........

product numbers: Gas control valve is Honeywell VR8204M, Ignition module is Honeywell S8600M.

larry_9

check ground

some times if you don't have a good ground it could happen

Unknown

John with those controls

do the following:
Check ignition cable and make sure it is not cracked or brittle, check the ceramic on the spark igniter to make sure it does not have cracks or breaks, clean the rod as I said before.

Make sure the igntion cable has continuity, it can get the high voltage signal through many times but the small microamp signal can not jump across a break.

Go from the tip of the igniter to ground "YOU SHOULD NOT HAVE CONTINUITY" if you do it is grounded.

Ignition system grounding go from the GND terminal of the module to ground (use the gas valve for ground) "YOU SHOULD HAVE CONTINUITY" if you do not then establish a ground by running a wire from the gas valve to GND burner terminal on the module.

Set you multi meter to measure DC microamps (usually the lowest scale on DC amps scale) put the meter between burner ground connection on module and the wire you pulled off burner ground. You should read between 2 to 10 microamps normal is 3 to 5. If less than 2 and you have cleaned the flame rod then replace the pilot assembly. If you have 3 to 5 and the problem still persists then change the module.

Matt Undy

Gas valve

I'd check to see if there is voltage to the coils in the gas valve when it shuts down to see if the control is failing to call for the valve to open or if the vlave is failing. I've seen solinoid coils become intermittent rather frequently in all manner of applications.

Matt

Marc Holley

Do you have a mechanical thermostat or electronic? If mechanical this could be a heat anticipator problem, set wrong, at the thermostat.