I have a 3 zone system and two of the zones work just fine. On the third, when the thermostat calls for heat, the zone valve opens, but the pump does not kick on. Confuising since the other zones work just fine. I know its not the thermostat or the pump. Can the valve zone have an electronic problem that never tells the pump to engage. Any suggestions as to cause/fix?

What kind of zone valve do you have? Are they honeywell? Can you post a pic? Most zone valves have two TH connections that, when powered, open the zone valve. There there are usually two END SWITCH connections, wich should close when the zone valve is fully open. If the end switch is bad, or the zone valve is not opening completely, the pump will not kick on. Try jumping the two terminals marked end switch, and see if the pump kicks on. If it does, you may be able to replace just the zone valve head and solve the problem.

Thanks for the feedback. It's a Hollywell... see pic's

Yep, standard honeywell zone valve. Good valves, but they do fail over time, like any thing else. Did jumping the end switch start the pump? It should.

By jumping the end-swiches... do you mean to simply touch a wire to the two "end" switch terminals? If yes and the pump fires, does that mean the electronics in the valve are shot? If that's a yes also, can just the electronics of the valve be replaced without removing the entire valve from the piping and having to purge the system.

Thanks.. nice to talk with someone with knowledge on the topic.

OK, I jumped the end switches as you suggested... and you were right, the pump fired up. So I assume the electronics on the valve are shot. To repeat my earlier questions, can the electronics part of the zone valve be replaced without having to drain the system, remove the entire zone valve (unsweat) and solder in a new one?

Yes, you can replace just the head, not the guts of the zone valve. There is a screw on the top left and bottom right of the zone head, unscrew them and simply pull the head off (may take a bit to pull it, but don't worry you won't break anything). This will not be breaking into the system. Now, I suggest leaving the wires hooked up and when you have the head off, see if when you turn that stat up, the pump will start. If it does, you will need to replace the guts of the valve, meaning you would have to break into the system unless you have isolation valves on top and bottom of the zone valve. This still doesn't require soldering in a complete new valve, just take the four nuts off that are under the head, and pop that part out and replace with a new one, including the o-ring. Hopefully you can get away with just the head. Here's a quick test, if you can spin the shaft with just your fingers (the shaft you will see once you get the head off), then you should be good to go with just a new head. If the shaft is stiff and requires pliers to turn, it is getting tight. You can try some lubricant (wd 40, etc) on the shaft and work it back and forth to see if it will loosen up. If it does, give it try with the new head. If it stays stiff (remember, it should only turn about a quarter turn) then the fact that it is getting tight may cause the head not to be strong enough to open all the way engaging the end switch. In fact, if its real tight, the head may be fine and all you need is the guts. That's why I say try the head with it off the valve body, if it kicks the pump on, then the head is probably fine. Hope this all makes sense. If not, easiest to just buy a complete zone valve (exact same one) and start by replacing the head, if it still doesn't work, replace the guts (shaft and ball, you will see if you pull it apart). Good luck, and please keep me posted.

Outstanding response to my issue! I appreciate you taking the time to provide detailed explanations of troubleshooting the problem and the fix. I'm jumping over to pexsupply.com to order the parts and feel much more confident that I can correct the problem. You're a true professional and I thank you for your interest in this matter. Happy Holidays!

Glad to help rickbuf. Let me know how things go, and if you need any further assistance, Im here usually at least once a day, after work. This site is just a hobby for me, but I deal with these valves on a regular basis at work.

Take care, Merry Christmas and Happy Newyear.

Wha-La! Received the Pex-Supply order, spent 10 minutes insalling it... and I was back in business.
Should anyone receive HVAC support from MYGIRLSDAD77... believe him... he knows his stuff and I thank him for his help.

Thanks for that rickbuf, I really do appreciate it. And thanks for the update, always glad to hear of the outcome, especially when it works out so good.