Gas furnace won't start.

[KinzeMech]

I could use a few suggestions.

I have an approximately 35 years old Bryant natural gas furnace. We had our first chilly day the other day, and while I wasn't ready to turn it on for the season, this is usually the day I give it a half day test run.

It will not ignite, nor attempt to ignite.

It has an automatic vent damper. Instead of opening 90 degrees and then stopping, the vent damper is simply rotating continuously. Is it possible there is a malfunction in this vent damper, and the furnace is not starting because it is not receiving a signal from the damper that it is "open"?

It is an electronic ignition system, and makes no attempts to ignite. The model number is 397EAW036080, but I have not had success looking for a manual online.

Looking for suggestions. Thanks!!

 

[Hpozzuoli]

Is the pilot lit?

 

[KinzeMech]

Electronic ignition, no pilot to contend with.

 

[KinzeMech]

Following the wiring diagram, it appears that the vent damper interrupts the same circuit as the high limit switch, therefore if the vent damper fails to signal the vent is open, the system behaves the same as if the high limit is tripped.

Jumping the wires at the vent damper (after manually verifying the damper was open, and it's motor unplugged so it stays open) caused a normal ignition, so the system is presently running it's first cycle of the season.

 

[KinzeMech]

I have no idea what changed, but after running it a few cycles with the vent damper wires jumpered, I plugged it back in, and it works normally. When the stat calls for heat, the damper rotates 90 degrees, stops at the open position, and then the burner ignites. When the call for heat ends, the burner shuts off, the damper rotates 90 degrees again, and stops in the closed position.

I don't know what caused that, but I'll take it for the time being.

 

[LS6 Tommy]

Is it an Effikal draft damper actuator? That's common with them, which I think are what Bryant used at the time. Constant rotation is either from an intermittent signal from the T-stat or a bad damper. Given the age of your furnace and the fact that you said jumping it out allows the furnace to run, I'd say the damper is worn out The end switch on the stack damper isn't making. IIRC, it tells the damper motor to stop in the open position & also makes the safety circuit on the burner control. Some have a "Hold Open" setting. You can turn the power off, GENTLY manually turn the shaft in the direction of the arrow with a wrench until it gets 100% open, then flip the switch. I don't remember if you can do this to solve the constant spinning issue. Here's some troubleshooting info:

http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/service-bulletins/sb0201.pdf


Tommy

 

[KinzeMech]

The only name on the damper box is "Carrier Corporation"
The model number is 306234-307.
It's plug matches the one on the first page of the document you linked, including the two pins it said to jump, where were the same ones I determined to jump after staring at the wiring diagram for a while.

Unless it gives trouble again, I'm going to just consider it a switch that was a little sticky after sitting uncycled for 5 months.

Thanks for linking that document. I'm going to print a copy and it's going in my furnace file.

 

[LS6 Tommy]

The only name on the damper box is "Carrier Corporation".

Makes sense. Bryant is one of the lower level Carrier brands.

Tommy