Leave the thermostat in place and the wires connected normally.

When the power is on but the thermostat circuit is open (that is, NOT
calling for heat) you should see 24VAC across the thermostat terminals.
When the thermostat is closed (calling for heat) you should see zero volts.

coldguy wrote:
Hey there,
I'm having problems w/ my heating (as discussed in a previous thread),
and I want to double check the connections between the thermostat and
the boiler isn't the problem. I'm almost sure the connection is fine
(the boiler clicks whenever I set the thermostat above the current
temperature, or below the current temperature), but I want to have
direct measurements that show me that the connection is solid. What is
the best approach to doing this?

I just purchased a multimeter, with the following idea in mind -- hit
the breaker on the power to the thermostat, disconnect the R & W
cables from the thermostat, place the multimeter to 50V DV (the
thermostat is 24V, 50 the closest higher reading in the multimeter),
flip the breaker back on, and then place the black test lead on the W
cable, and the red test lead on the R cable. If my understanding is
correct, this should complete the circuit and my multemeter should
read the voltage level.

Does this make sense, or am I misunderstanding how this works? I'm
working off of reading about cabling and doing electrical work, but
all the voltage meter docs I've seen are for wall sockets and such. I
thought I'd ping the experts before causing any havok.

Thanks