Need new t-stat or is it wiring problem or both?

D107

Got a call from the family house that there was no heat in back porch. (Circuit 2). Old Honeywell Chronotherm (with clockface on it). As far as I can remember clock never worked which was OK since it was always kept at 60 deg except when company was over. it's a little lopsided to boot. In addition to which my mother says that since it's hard for her to reach the day/nite tabs over the couch in front, so she was moving the tabs when the need to arose by slapping them right or left with some kind of stick. (I think I once saw this procedure pictured in the instruction booklet under 'smacking your thermostat'). I had her move both day/night tabs all the way to right, check the Taco <span style="color:#000000">SR503-EXP Switching Relay</span> at the boiler and the circuit 2 light didn't come on. So I had her move the tabs all the way left and then right again and that did the trick for now.



Anyway, it's old and I'm happy to pick up a new t-stat and install it myself--I'm sure there's only two wires. Heating system is fairly new Buderus G115/21 riello 40 F3 with outdoor reset, 2 circuits each with own Chronotherm. Before I do that though I thought it would be good to trace the wires to wherever the transformer is and check the voltage and see if that's the problem--perhaps that's why the clock doesn't work; perhaps the W and R wires are reversed or simply a fastening screw is loose. I assume each t-stat has its own transformer? What tool do i need to check this voltage--'ammeter'?? I figure I'll try to do it right the first time and learn a little in the process. The main t-stat was completely re-wired with the new boiler and works fine.



Any thoughts?