[manixc]

Hi all, this is my first post.

I have a Lennox G27M (it's about 9 yrs old) and it's been having some problems.
It's a two-stage gas furnace and 80% efficiency.


The problem is as followed,

I have been getting the "Rollout switch open. OR 9-pin connector improperly attached" diagnostic code or the "Primary or secondary limit switch open." diagnostic code. Depending on the mood of the furnace, it's one of the two codes.

This is what the furnace does,

The furnace start and get into 1st stage, after ~10min it goes into 2nd stage high heat, and then the furnace stop after a while and flash the diagnostic code above. This repeats for a while, till either the furnace just stop or it works again by itself.

The weird thing is that the furnace will work again without any problem after a while (from a few hour to a day). This is the part that bug me!

I had a Lennox technician over to look at it on last Thursday but the furnace was working. The tech checked and cleaned the flame sensor and checked the voltage of other things and said the furnace is working okay.

The reason he said why the furnace was behaving this way is because the furnace is in the garage so there can be some condensation(water vapor) build up that effect the pressure or something, or the flame sensor wasn't reading the fire properly.

Well, the furnace seem to be having the issue again, and I am wondering if there's something I can do other than getting the tech to look at it again(since service charge is expensive and the furnace might just decides to work again).

It seems to me that this happens when the weather get colder than usual or just cold. I live in Surrey(suburb of Vancouver, Canada).

Also, this happen last winter as well and we have a tech over, and he replaced the main limit. That fixed the problem then, but now I'm not sure if replacing the main limit was the cure.

Oh, filter is clean as I cleaned it when I notice the problem. In fact, I took the filter out for now.

Thanks.

[labman]

Maybe it is the 9 pin plug. Is there a bundle of wires running from the gas valve area to a plug on the control board? Pull it off and clean the contacts the best you can. Then firmly reseat it. Cross your fingers and put the cover back on.

[manixc]

Maybe it is the 9 pin plug. Is there a bundle of wires running from the gas valve area to a plug on the control board? Pull it off and clean the contacts the best you can. Then firmly reseat it. Cross your fingers and put the cover back on.

Thank you. But the furnace is working again (for whatever reason), so I'm not going to touch it. I will keep this in mind.