zone 3 only- fan stays on all of the time

[DT3]

I have an EWC model UZC4 with 4 zones in the house. I have the dip switch setting set to ANY. The system works with any of the other zone fan controls working properly except that the thermostat (honeywell RTH8500) to zone 3 can not toggle the fan on/off..(fan stays on..and I see the Zone 3 Open LED is lit). I tried switching that thermostat with another one and it does the same thing). I verified the wiring to the thermostat is the same as that of the other thermostats in the house. I never noticed this unit now but it might have always been working like this. Do you have any suggestions? Thank you.

[Pcyrana]

Is your Fan LED lit as well?
If you remove the G wire from the zone 2 thermostat terminal block on the zone panel, does the fan turn off or continue to run?

[DT3]

Thank you for your fast response.

1.The fan LED is lit as well.
2. When I remove the G wire from the zone 2 thermostat terminal block on the zone panel, the fan continues to run (no change).

Thank you .

[Pcyrana]

What happens if you remove the G wire from the zone 3 terminal block?
Does the fan continue ro run?

[DT3]

I removed the wire from Zone 3 block. The fan stopped and all 4 zone open LEDs were lit as well as the bypass damper LED. When I connected the wire, it reverted back to Zone 3 open LED lit with fan LED still on (same as previously).

[Pcyrana]

Due to the fact that you have already tried to swap the thermostat out it sounds like you might have a wiring issue on zone 3.
Do you have a voltmeter you can use to check for a short on the zone wires between the thermostat and the zone panel?

[DT3]

I have a short on the red and green wires R/G. What are my options besides running a separate cable since the cable run would require opening up walls. There are no spare wires left as all of them are going to the terminal block(s). thank you.

[Pcyrana]

You can simply remove the G wire from the thermostat terminal block.
This will prevent you from having the option of running the fan only in zone three.
The fan will come on as necessary when there is a call for heat or cool.

[harrybro]

thanks for information...