Strange behavior on one zone only (of 5 zones). When the thermostat on the zone on which I have a 3-wire Taco valve calls for heat, the pump kicks on, flue opens, boiler kicks on, and pump shuts off. (Sometimes even before the flue opens fully). Pump quickly turns back on and a few seconds later, shuts off again. Repeats a few times, till it stays on long enough for the boiler to stay on.

All other zones are working fine and I have the Taco valve manually open. I'm assuming the end-switch on that valve is flaky - makes sense? Since no other zone has an issue I'm eliminating the pump and the flue damper motor. It's a two year old system with an Argo zone valve controller. Anything else to consider? The installer did dress the wires from the Taco poorly - bent at a right angle where they join with the others on the way to the controller. Maybe an almost broken wire?

Thanks!

 

Possibly in the Argo also... what model is the control panel?

To eliminate the control panel as suspect you could 'swap' two zones, mover the thermostat and the zone valve wiring between two 'channels'.

If the problem doesn't move, it's the Argo, if it follows the zone valve, it's the zone valve (or even thermostat?)