How do I troubleshoot the blinking yellow LED light for zone 3 on a Honeywell HZ322.

Go to zone 3 and see if any air blowing out. Likely have a stuck damper. If you can access the dampers tap on the duct or motor a few times, maybe free it up.

Chances are it's a bad daamper. You can bypass any tstat by wiring red green and yellow together. Bypass the tstat, if still blinking you'll know it's the damper. You can then swap that damper to another zone and be sure the new zone then starts flashing.

Keep in mind you have the same terminals on the damper. 1-4-6. be sure both board and dampers are wired the same for spring open/power closed. I cant remember if that 311 sends power with a call or not( if power is being sent when light is on), but once you have double checked the damper wiring either verify with a meter that power is being sent or verify air flow. if it is then backwards simply reverse wires on board. I suspect it sends power when light is on, that is why zone 3 is lit. (there is no call for cooling on 3, therefore it is shutting the damper) YES, the damper that is not really there. Let me know, hope this helps. The damper that is trying to cool should NOT be getting any power, wire accordingly.

Be sure all zones are calling for cooling. Press the purge override and verify air flow on all zones. If one is still not working verify the board is sending voltage to that damper. A meter is a huge help but if all lights are on chances are the damper is stuck. You should be able to free it up but it will just happen again. Either replace damper motor, replace damper or if you can figure out if it is a "spring open" damper, get it open and unhook the wire to that zone. This will keep it open at all times because it can not "power close". Provided that zone CAN stay open all the time. Keep me posted!!

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Choose two colors of the thermostat wire, and connect them to the NO and COM and connect them to the zone control board leads for the zone intended. Almost all zone valves spring return open when deenergized. So ensure the zone valve is open with the system is off. At the base of zone valve there is a set screw that needs to engage the damper valve shaft in the open position with the motor in the spring release position. Most zone valve are 90 degree moment from full open to full shut. If you have a Carrier zone valve, they go full open to full shut in 45 degrees of motion. Your open stop need to be set so the valve stops in the full stop position.
To help understand the operation of a zone system, say you have 2 zone system and zone 1 thermostat initiates a heat or cool demand. Zone 2 valves energizes and shuts and zone 1 stays open and allow air to heat/ cool zone 1. If zone 2 thermostat simultaniously initiates the same heat/cool demand, the zone 2 valve opens and both zone heat/cool. When either thermostat is satisfied the opposite zone valve closes and when both thermostat are satisfied both zone valves open.
Hope this helps you understand zone operation. The same works for higher multizone systems.

No, more than likely it is the plastic wheel and I have found no available replacement parts for that. Honeywell did an amazing job with providing a quality product that will fail after 3 years

check the board for 24 v.a.c. or whatever voltage is used to supply this board,normally its 24v.a.c. from a small transformer,if this transformer burns open the thermostat will not operate

On the zone damper motor, there should be a little lever allowing you to open the damper for emergency heat. Probably a bad zone motor or connection.

No. If it's power open and power close you need 3 wires at both locations. If it has a spring you could get away with 2 wires. Depending on how hard it would be to run a new wire you do have the option of changing the damper.

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there is a "zone a lone" switch on the upper right side of the panel. Make sure it is in the "occupied" position. I believe that is up. If that doesn't work reply back.