Goodman GMP100-5 Rev B
Serial 9806614094

I believe this is a Gas(natural)/Heat pump combo. I think normal heat is set to use the heat pump and there is an "emer" option on the tstat that uses the gas.

Problem it had: blower was constantly on even with tstat disconnected and no heat. Checked out the status light, it was blinking 4 times.. which directed me to a bad or open limit switch. I took the switch out and checked the continuity on it, it was indeed open. I tapped it a few times and it tested as closed. Put it back in and plugged in the furnace and it fired up. Since it fired up, I was curious to why it was open in the first place. Checked the filter and there was no filter in there. Put a filter in and turned the furnace back on. Everything is in working order but the thing that concerns me is --

Everything comes on in the order it is suppose to, the flame starts and will stay on for about a good 5 minutes (in the mean time the status light is solid which indicates no problem) and after 5 minutes or so the flame will shut off while the blower is still on along with the vent blower. After a minute or less the flame will turn on again. It's very consistent in the time it turns on and off.

The house is very cold.. probably 59 degrees and I set the tstat to 70 to bring it up to temp.

I just want to know if this is the normal and if it isn't, what I should check/do.

Thank you

I forgot to mention, when the flame turns off the status light changes from solid to 4 blinks (limit switch). But after ~30secs-1min flame will turn on again and status light will be normal. Repeats it self.

After thinking about it.. I have no idea how long I used my hvac system without an air filter. Probable cause = coil gunked up.. restricting air flow causing excessive heat. I'll have to check that out

After thinking about it.. I have no idea how long I used my hvac system without an air filter. Probable cause = coil gunked up.. restricting air flow causing excessive heat. I'll have to check that out



Good thinking,, a dirty coil will not allow enough heat to flow through,also will cause furnace to overheat and cause the limit to open

Another question. Is it normal for the inducer motor and blower to turn on at the same time? I typically hear the inducer turn on first, then his, then flame, then blower.

Why would both turn on at the same time or is that normal procedure on this furnace?

Thanks!

No,, maybe because of the open limit,, and it might need to be reset,, power turned off, wait and then back on,,