Thermostat or Zone Flow water Valve issue?

Have a furnace that has 3 zone flow water valves for all 3 floors of house with a thermostat on each floor. The basement/bottom floor is having issues. Need to know if you think I need a new thermostat or a new valve. When I turn up the thermostat, the valve will not "kick in" or turn over. When I manually move the bar on the valve, it will kick in or turn over, but only for about a minute. The baseboard will heat a little but then the flow valve shuts back off again.

I will need to call someone in to try to fix it, so I would like to have a little knowledge of what it could possibly be so I don't get stung for repair bill that is unncessary or too high.

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Heard ya the first time A bit of advice..... don't go with who has the lowest service call fee. Don't go with the highest either. Ask around and see who others use to maintain and repair their systems. Don't bother with looking on BBB website, if the contractor pays 'em enough they get an A+ rating even if they are a POS.

Power open, spring return. Got meter?

Thermostats are simply temperature operated switches. Assuming it is a 2 wire set up (no cooling) short the two wires together. If the zone heats fine (and will continue to heat until you take the wires apart) then the thermostat is the problem. If you still have the same problem it is in the zone valve. Unless your thermostat wire is compromised in some way.

Hey, just because the BBB gave "Hamas", the terrorist group, an "A" rating....

(in quotes because it was a sting operation).

"In an investigation that aired on 20/20, ABC News chief investigative correspondent Brian Ross found that a fictitious company named after the terror group Hamas was able to win high ratings under the BBB's rating system, while other businesses, including parts of famed chef Wolfgang Puck's culinary empire, seemed to have been slapped with failing grades because they hadn't paid up.