Hi,

I have just recently bought a Goodman GMH81155CNAG gas heating furnace. I find the manual is very unhelpful as far as diagrams and explanatory.

The problem that I am having is when I closed the doors for the furnace, the heat would stop and only the blower running. The LED would flash four times repeatedly. The troubleshooting manual says:

Flash 4 times = Primary limit circuit is open

Possible cause = 1) insufficient conditioned air over the heat exchanger, blocked filters, restrictive ductwork, improper circulator blower speed, or failed circulator blower. 2) Faulty primary limit switch. 3) Loose or improperly connected wiring.

Thanks to the invisible explanatory diagram from Goodman, I don't know and even how to find the "Primary limit circuit switch".

Better yet, on the wiring diagram. It states: when flashing 4 times = Open High Limit. It is so greek to me and Goodman does not provide any user support on their website.

I would appreciated it very much if you could help shed some light.

Thank you.
Jay = [email protected]

How old is it? Isn't it under warranty? See the sticky post on top of the main page for pictures of a main limit and causes and corrections of furnace overheating.

The entire heating system is brand new out of the box. Here is what I have observed:

1) the heat flare to the side of the heating nossle
2) Manual states, a filter must be installed, I can't find a place to put the filter.
3) The heat turns off and on after I put back all the front covers (2, top and bottom) for the heating unit. However, when I take off the bottom cover exposing the circuits and air blower and hold down the switch then the heat would run non-stop (30 minutes test).


I don't see any openings for air to get into the blower and I think it is lack of air flow to the blower. On the regular heat, you would have and opening for airfilter which is next to the air blower. This system doesnot.

Any idea?

Thank you.

Hi NorthernHeat,

I have asked a few prof and they said that I have to cut a hole on the side wall for the filter. So, I will stop by the heating shop for more infor. For this situation.

Thanks for your help.

Jay

Wow, I would have never guessed there was no hole cut for the return air to come into the furnace. I guess, if you had told me you installed this yourself, I might have thought of that. (not)