1 zone is returning cold

buz1699

I have one zone that is returning colder. Trying to troubleshoot. I purged the Boiler to remove any air that may have been trapped. Replaced thermostat and still having trouble. Was thinking it may be the valve header not functioning properly. I opened the valve leaver to bypass and the hot water runs out and returns at the same temp. What's troubling me is that when the leaver is up it does call for heat on that zone but the return is luke warm.

Harvey Ramer

Can you post pics so we can see what you see?

buz1699

Boiler is 18 yr old, Oil heat, Zone valve is 4th to the right

Harvey Ramer

If hot water runs out through when you open the bypass lever but doesn't on a call from the thermostat, you either have a wiring issue or the zone valve head needs to be replaced. The head can be removed by depressing it slightly and rotating maybe a quarter turn.

Harvey Ramer

Do you have a multi meter?

buz1699

No Multi Meter, Hot water does run through when the by pass lever is up but returns cold. When the level is down it also runs out hot and returns hot.

Jamie Hall

By "runs through". Do you have a way to actually measure the flow through the zone, or are you measuring the temperature only? Because if the return is cold that could mean -- probably does -- that there is no flow, and the valve is not opening.