Ignitor Position - Gas Goodman GMP0753

Thanks folks! Appreciate the quick replies!

SuperTech said:

My suggestion is to be prepared to replace the furnace. . . . usually an indication of heat exchanger failure. Please don't operate the furnace until a professional checks it out. I'm concerned about carbon monoxide poisoning.

I understand these Goodmans or generally good, but the exchangers may fail quicker than on others. Discussed with the tech last season and he suggested it still has / had some life in it. We have a CO detector, but I have requested a call when folks get back to work tomorrow. Seems like often I need professionals on Holidays and weekend! ;-) (It's a bit chilly here not to have working heat.)

JUGHNE said:

Was the draft inducer fan running?
Was the pressure switch jumped out?

Yep - inducer is fine, and the lockout is in place. Replaced it last season - and tested the switch then.

HVACNUT said:

Since you captured it, it's not the first time.

. . . .

Those flames are low down. Can you post a pic farther back?


The rollouts should have open the circuit immediately.

Actually - based on a sound - I suspect it's been doing this for some time. The change was gradual. Had I not worked on the humidifier yesterday I'd likely not have noticed the issue.

The flame in the exterior shot align very closely to the interior picture above - if anything a little lower. The "louver" in the cover might also direct it downward.

If I understand the (typical) rollout - the sensors are often above where the flame is. If the flue is blocked the flame, I thought, would tend to be near and above the openings in the interior shot.

The flame in the image is very short-lived. I stepped through the cell video 1 frame at a time and its all over in about 5 frames.

. . . Not sayin' that's good of course, but it may be why the rollout sensor isn't tripping. (I'm going to go look at that more carefully.)

I appreciate the advice - and it now seems that much more urgent. I do take it very, very seriously. While it certainly should be checked out, I do observe that moving the ignitor slightly toward center seems to have dramatically cut the flame I can see outside the unit - to nothing.

When the tech comes I'll share the little I've done and my observations. (I'm a decent mechanic, but spent much of my career partly doing customer support of software - so I think I get it.)

Thanks again for the prompt responses, the explanations and warnings!

SuperTech said:

Just don't put all your faith in the CO detector.

Yeah ... just saying to the wife it might be worth picking up a new one. I don't have tools to check mine (I worked for an outfit that made portable, wearable CO and other gas detectors at one time).

I want to add a little more information from another look-see. (Others may refer to this later.)

HVACNUT said:

Can you post a pic farther back with the door off to show the whole burner compartment?

So here's the "business" part of the interior with the front panel alongside for reference. The burners are pretty low relative to the grill. The ignitor is on the right, and there's a solid horizontal plate (green arrow) covering the area well - between the burners and the gas valve - running from the back to close to the grill. The flame seemed to be coming out the lower right corner of the grill in the images above.



This is the full interior, upper half of the furnace. Blue arrow indicates what looks like the rollout sensor. Assuming it's good, I'm not sure why it's not tripping. (Plan to ask the tech.) But, as you likely know, thinking about electrical motor controllers or fuses for motors, there's some curve where the current can spike over the nominal rating, but it has to be sustained for some period of time to trip the protection. Motors draw a lot of current until they get up to speed. Might this be similar?? Definitely saw flames, but 6 video frames at 30 fps is about 0.2 sec in duration.

One last observation. I nudged the thermostat to watch the furnace, with the cover off. With the ignitor tipped slightly closer to the center**, the "rollout" is minimal. BUT, I noticed the furnace cycled - i.e. the ignitor came on, I think I heard the gas valve open, but no ignition so the flame sensor caught that. The inducer fan clicked off for a second, and it retried the cycle - this time igniting. My wife said she thought she noticed that at least one other time this afternoon.

I suppose in the short term, given the choice between an extra cycle to ignite and flames shooting out through the grill ... I'll go with the former for now!

Again - Thanks - I'll post when the tech looks it over...

** I stuck a piece of copper wire under one end of the plate holding the ignitor - you might see the black insulation I left on part of it - and snugged the screws down (unevenly) to moved it left slightly.