Our hydronic heat system is working fine for one zone only. The second zone will only switch on 30% of the time that the thermostat actually makes its call. In order to make that zone work, we have to cycle the power on and off to the board by flicking the power switch.

We have replaced the zone control module circuit board, thinking there was a short somewhere. No change.

We have replaced the valve, thinking that it was faulty. No change.

We have replaced the wiring that leads from the valve to the zone control module thinking there is a fault there. No change.

We have doubled up on the low voltage wire for the 'close' end switch, thinking there is a loss of voltage over the run. No change.

We can't seem to find any repair company that can fix it and we have spent hundreds of dollars chasing down the problem.

The call is made and only answered sporadically on that problem zone. Meanwhile, our other zone is functioning perfectly off the same board and the same equipment.

Any suggestions would be greatly appreciated.

It seems you have replaced everything but the thermostat. Buy a CHEAP heat only thermostat and disconnect the old one. Then run the wires by jumper if necessary to the new thermostat. See if that works out for you. Just make sure the old thermostat is completely out of the loop so it can cause no interference.

Replaced the thermostats, too. :(

The signal problem seems to be from the new valve back up to the board. The valve will open every time when it calls, but the positive connection to make the heat come on never happens.

Replaced the thermostats, too. :(

The signal problem seems to be from the new valve back up to the board. The valve will open every time when it calls, but the positive connection to make the heat come on never happens.

There is a end switch in that Honeywell zone valve. They are usually bad or good but I would check it out to make sure it is tight in the valve switch assembly area and not moving around which would allow intermittent operation.

There is a end switch in that Honeywell zone valve. They are usually bad or good but I would check it out to make sure it is tight in the valve switch assembly area and not moving around which would allow intermittent operation.


Thanks. I just checked it and the interior part of the switch where the wiring contacts the assembly seems to be making a noise like something is loose as I move the wires around.

I'm going to spend some time removing the assembly and checking the connections.