Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

No heat zone 2

mow Member Posts: 12
i have three taco zone valves with one circulator pump. There are no special controls on the weill mcclain 140kbtu gas boiler.

When thermostat calls on zone 2, I get 24v between 1 and 2 terminals and a minute or two later I get continuity between terminals 2 and 3. However the boiler will not fire and the valve will not open. The only way for me to get heat to zone 2 is to manually open the valve and wait for another zone to call for heat.

when i manually open zone 2 valve, I hear water flowing but it sounds restricted, like the valve is only partially open.

The wiring is as follows. White from tstat to valve terminal 1
Red from stat to 24v transformer.
Valve terminal 2 to 24v transformer and to trans g wire.
valve terminal 3 to wire labeled transformer.

Nothing has changed in the wiring and this unit ran fine last year.


  • STEVEusaPA
    STEVEusaPA Member Posts: 4,963
    If you have continuity at the zone valve, disconnect the wires 2 & 3, at the zone valve and twist them together. If the boiler doesn't fire, disconnect those same wires at the aquastat (T-T or X-X), and jump those terminals at the aquastat.
    If the boiler fires, it's the wires. If the boiler doesn't fire, it's the aquastat, again, IF you have continuity on 2 & 3.
    No continuity on 2 & 3 & 24v on 1 & 2 would mean its the end switch in the zone valve head.
    Make sure power is off to the zone valves (might be different disconnect than the boiler) when removing wires from the zone valve.
  • mow
    mow Member Posts: 12
    edited November 2018
    With the tstats all switched off, every zone valve has continuity between 2 and 3. Boiler not firing.

    With the wires still attached to the terminals on valve 2, I put a jumper from terminal 2-3 and the boiler fired(even though there was continuity between those terminals)

    Scratch my head
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!