comfortmaker pilot lights but not burner

jasonzzz

I've got this Comfortmaker furnace in the attic space, I've got it matched up to a NDN3/NDF series. It was installed around 4 to 5 years ago.

It has what appears to be an intermittent pilot, the draft fan kicks on, then the honeywell control module signals the igniter to spark and the pilot lights. The main burner is suppose to light after that, but it is not lighting (just the pilot is lit), it continues sparking and retries, then stops. I haven't
experienced a complete lock out yet. From looking at the pictures on a couple of websites, the pilot/sensor assembly looks different than most. There's only a single lead coming from the assembly and it looks like there is a combined igniter/sensor on the same rod.

Is this right? I am thinking it is this part that has the problem.

redline

check the sensor.

jasonzzz

where can I find the off/on ohm readings for this sensor? TNX

bigMikeB

It isn't that kind of sensor, it passes @ 4-10 microamp current through the flame to the control to operate.

jasonzzz

ah. ok, I am reading up on about flame rectifiers now... seems like it would be tough to make the measurement, it's going to blow my multimeter unless if I do a bypass and flip it over after the flame is lit...

bigMikeB

Your meter would have to read microamps, doubt you have that scale unless it's an HVAC speciality meter like a Fluke 116 or 902.

jasonzzz

oh yeah, mine only reads mA, dang... Guess I won't be doing that.

I'll take out the ignition rod and clean the rod and flame hood and see if that makes a difference.