Comfortmaker furnace issue: advice on how to proceed?
I am a homeowner having trouble with a Comfortmaker furnace, and I am not trying to repair it myself (so don't worry). But I do need some advice. I've been working with one HVAC repair firm, but they haven't been able to solve the problem.
This is a two-stage Comfortmaker gas furnace. It's in the attic and installed lying on its side. The model number is: NTP6075GFB1. It is not a condensing unit.
The problem only occurs intermittently - sometimes it will work fine for a day or two, and then the problem will continously occur for a half-day or so. Here's what I hear when the problem is occurring:
- I raise the temp on the thermostat and it clicks on.
- The draft fan starts running immediately.
- The blowers never start blowing.
- The draft fan shuts off after about 90 seconds.
- It tries again and repeats that cycle about 5 minutes later.
I've had several technicians from one firm come to my home over the last few weeks trying to solve the problem. First, they were certain it was the igniter. They replaced that, and it didn't solve the problem. Then they said it was the smart valve. Replacing that fixed it for a day or two, and then problem started again. They replaced that smart valve with another new one - worked for a day or two and problem started again. Replaced the igniter - worked for a day or two, then problem started again. They say they are stumped and are waiting for tech support to call them back. They don't think it's the board since the problem is occurring intermittently.
I've been up there myself just to collect some info for them. When the draft fan comes on, I don't believe the pilot is igniting, but I'm not certain. I did smell a moderate (but not large) amount of gas when the furnace should have been firing up. After the 90 seconds, the furnace goes into a soft lockout and flashes a 6+1 code. Nothing on the sticker on the door talks about that code. The sticker mentions 6 as the soft lockout code. But the sticker starts with the heartbeat, then proceeds to 2 flashes and 3 flashes which are for low pressure switch stuck open or closed. There is no indication of what 1 flash might mean.
I'm not sure how to proceed. These guys can't figure out what the problem is. They mention the board but don't seem at all certain that that's the problem. I ask what else might be the issue, since we now know it's not the igniter or the smart valve, and they don't have any ideas.
Do I need to work with a different firm? Or does this sound just as unusual to you?
Thanks for any assistance that you can provide. This has been going on for weeks, and it's driving my family and me crazy.