We have a Sears gas boiler, which supplies 4 zones of heating in the
house through W-R zone-a-flow valves . We are only concerned with 3
here, as one is deliberately turned off.

We have well controlled thermostatic heat in 2 of the 3 zones, but we
did not have any heat in the garage, which has its own zone. Yikes --
with 10-yr record low temps here, we had to save the pipes!! The
thermostat in the garage was a bit beaten up, but no matter how I
manipulated the dial, the heat did not come on. I had the good sense
to check the White-Rodgers zone-a-flow water valves, and discovered
that, while the functioning zones' valves were open, the garage zone
valve was closed, so I manually opened it. Voila -- heat in the
garage! We are saved from doom (so far). The once frigid garage is
now recording temps of 50-52 degrees -- if that gets us over this
Siberian cold blast, fine. But I was kinda hoping to bring the temp
down to 40-45 degrees, or so.

Any way to get the thermostat to put out any temperature but 50
degrees? ANy idea why the W-R zone-a-flow valve did not open in
response to the thermostat, and had to be operated manually?

All the thermostats in the house are W-R 125-202 -- clearly an ancient
mode. I replaced the beaten up one with one I knew worked fine (from
the zone we are no longer heating), but the darned thing does not
control temperature any better than the beaten up one.

Clearly, the easy course is just to ignore the problem until the
Siberian front retreats, and take it up the wazoo for paying to heat a
poorly insulated garage to 52 degrees.

I checked for loose wiring on thermostat and zone-a-flow -- and
everything seems to be nice and tight.

Will upgrading to a more modern thermostat help? Or is it a deeper
wiring problem? Could it possibly be the garage zone-a-flow valve
malfunction (I checked the wiring and everything eems tight)?

Advice, O Home Repair Gurus, I humbly request.