[philipk65]

Hi,
Last week I had two of my threads combine and confused everyone, so here's an update.
I have a York Diamond 80 furnace dual zone (2 thermostats).
The downstairs stat starts the furnace fine, blower starts in 30 seconds heat comes out. In exactly 2:40 seconds the system (flame) shuts off and the blower runs for 4:30 then turns off. Immediately the system (flame) comes back on and the cycle repeats.
However, the furance works GREAT from the upstairs stat. The furnace fires blower start in 30 seconds ran for 11 mins. warmed the upstairs 5 degrees then blower shut down in 40 seconds. PERECT!
I've tested the flame sensor and it read 4.2 mil amps.
What else can it be? The furnace control board? (I have no codes blinking) or even the equalizer control board that works furnace from both stats?
Thanks!

 

[yuri]

It sounds like it is cycling on/off with the high air temp limit switch.

Probably the downstairs stat is not opening a damper motor and allowing enough airflow.

The upstairs one must be allowing a damper to open and then it has enough airflow.

Zoning systems are not all alike as some have bypass dampers which may be motorized and other use air pressure.

Point is it sounds like a airflow problem causing it to overheat.

 

[philipk65]

Both my zones have motorized dampers. How do I check the dampers for opening
efficiently?

 

[yuri]

That can be complex. If the zoning board is failing to open them that could be the problem. Could be the damper on one of them is broken or the motor is shot or has stripped gears etc.

You may have to call a tech as I cannot see them or walk you thru that. Too many different types of zoning boards and systems to cover all that.

 

[philipk65]

yuri, Today I removed the 2 damper motors and had the dampers wide open, furnace worked great in both zones!
Question I have is... before I took the motors out, one of them was really warm to the touch when the furnace was running. Is this normal?

 

[roughneck]

Could be normal. Does the damper cycle with a call?