Customer wanted an approximately 50 year old baseboard heater replaced. He claimed it worked, but half of it was gone, so he wanted a new one. I pulled the old heater out and found three two wire cables going into it; the supply line, the line going to the thermostat, and the line for continuing the circuit. So I figured out the proper connections, hooked it all up, it worked fine. Later on, homeowner says it doesn't work. So I tested the line going right to the heater, sure enough, it wasn't getting any power. I pulled everything apart, re-tested the supply line and still got 240V, so I pulled out the thermostat and hooked the wires together to bypass it, that would exclude the possibility of the thermostat being the problem. I checked the other end of the cable between the thermostat and the heater with my ohm meter, and it showed continuity, pulled the wires apart on the other end, checked again, continuity is gone, o.k so that part is fine. So I tried hooking the supply power line through the cable between the heater and the thermostat while I still had the thermostat pulled out and bypassed with a wire. Checked the leads going to the heater, read 240V, o.k good, I pulled apart the wire I had crossed in the thermostats j-box to open the circuit, then it dropped to 200V, while I was expecting it to go to zero. My consensus was there was something interfering with the cable between the thermostat and the heater. But I couldn't see what it was because everything is buried behind drywall. So I tried hooking everything back up like I had it to see what would happen. But I didn't mount the heater back on the wall, I just left everything exposed yet connected so I could test it. So I got the thermostat back in, heater connected, put my volt meter on the line in at the heater, turned on the thermostat, I read 240V and the heater turns on, o.k good. So I turn off the thermostat and expected it to go down to 200V like it did before, I turn it off and meter reads 0V, just like it's supposed to. So basically I have everything set up the way I had it in the first place when it worked, and it seems to be working fine. However I'm a little leary about it considering it quit working before, while I had it wired the same way, and the funny continuity test on the cable from the heater to the thermostat also worries me. So I'm going to leave it hooked up with the wires and everything exposed for a while and continue checking it.
But what the heck is going on with it? I don't want to mount everything back together and then later have the homeowner call me telling me it's not working. If I run into any more problems, I'm thinking the only thing I can do is forget that old wire going from the thermostat to the heater all together, and run a new cable for it, but if I do that, it will have to be in a different location which won't be very convenient.