I have a Goodman GMP 100-4 running on propane The last week or so, has seen some intermittent operation. The draft inducement motor comes on but at times no ignition occurs. Vacuum manually applied to the vacuum switch results in ignition taking place. Inducement motor area has been cleaned out. Originally found remains of a bat or bird in it.

I did notice that the gasket, (red baked clay looking stuff), that is on both sides of the plate that is on the back of the motor, has broken off in a couple of places. This looks like it would leave a couple of small gaps. Could this be the problem with not enough vacuum being created to operate the switch?

I was told that this stuff is high-temp silicone. I filled the gaps with some hi-Temp a few hours ago and the system fired right up and has run fine since.

But it also ran for a week after the initial cleanout before acting up again.

Yes it is high temp silicone. It may have been the problem. The best way to know is with a magnahelic gauge to see exactly what the vacuum pressure is.

Yes it is high temp silicone. It may have been the problem. The best way to know is with a magnahelic gauge to see exactly what the vacuum pressure is.


Thanks Heat. It seems to be working OK the last 18 hours or so. What should the vacuum range be? The place I retired from may have a gauge that I could borrow.

One other thing, this silicone gasket was very hard and crumbly. Is that the result of years of heat and aging or is it a special type for this application? It looks like red baked clay.

I used some clear Hi-temp silicone that I used for installing pellet stove exhaust pipes with, to patch the two gaps in this application. Am thinking that if I wanted to clean that backplate completely and replace it, that the stuff I used might make it real tough to take apart again for cleaning.

But I don't know what will happen with it after a while. Do remember that I needed to take some of my pellet pipe apart again and it was stuck pretty good.