View attachment 236093
I disconnected the center (TH/TP) wire, lit the pilot and measured 25mv initially climbing to 60 mv as the thermopile heated.
So, is the thermopile ok? So the problem may be the gas valve?
Cheers, Mike
Well I found the following reference to a B vented Vermont Castings Radiance 2600:
http://www.cozycabinstoveandfireplaceparts.com/cgi/display.cgi?item_num=2600-2603
Part #55 is listed as a spill switch, presumably checking for spillage from the draft hood. That kind of switch will typically shut off the pilot light if it opens ---and if you have a poor electrical connection, that's a good reason why the pilot wont stay lit, often enough.
The picture of the gas valve reveals that you have a thermopile system that powers a magnet to hold open the pilot burner gas valve and to open the main burner gas valve.
You have three connections on the gas valve: TH, TH/TP, and TP. TH/TP is the common or "ground" side of the circuit.
Voltage to the TP connection energizes the pilot burner magnet, to hold that open when you release the gas valve plunger, and that's probably in series with the spill switch.
So what you want to do is to measure the millivolts between TP and TH/TP after you've lit the pilot and it's had a chance to warm up.
My memory of what millivolts are needed to keep the pilot lit are hazy ----perhaps someone else can contribute that voltage.
You should be able to trace two wire connections from the pilot generator ----one to TH/TP and the other to TP.
You can see two wires forming a cable, one to TP and the other to TH. They should be going to a switch to turn on the main burner gas. Power from the TP connection turns on the main burner gas connection at TH if that switch is closed.
You should find a wire going to the spill switch attached to the wire going to TP from the thermopile.
If the spill switch opens, it shorts out the voltage going to TP and the pilot wont stay lit. There's a reasonable chance that a bad switch or bad wire is causing that wire to be grounded when it shouldn't be, causing your problem.