Gas stove wont light

I have a Vermont Casting gas stove with a Honeywell VS8420 valve on it. The pilot lights fine. When I turn the knob from "Pilot" to "On", I hear a clunk and the pilot goes out.

I'm getting about 27 mV at the tip of the thermocouple. I'm getting about 700+ mV at the Thermopile (between TP and TPTH). My coil resistance between TP and TH is 3.5 Ohms. I cleaned everything up but haven't been able to fix the problem.

At first I thought maybe I had a bad thermocouple or thermopile, but my mV readings are good.

Any ideas?

http://woodheatstoves.com/-p-12685.html

i just uploaded the book for you, see page 7 of the free pdf.....for the rest of the tests



is the unit b-vent? if so it might have a spill switch as mentioned above,

Thanks for the info. I jumpered out the spill switch. Same results, pilot goes out when turning knob on.

Another interesting note - when I jump TH to TPTH (with the pilot lit and the knob in the pilot position) I can hear the typical valve click, just like when it used to light. When I jumper it it clicks, when I take the jumper off it clicks again - but the burner doesn't light.

Any ideas?

what were the results of the other valve tests listed in the pdf i posted??

Test A (coil resistance): 3.2 - 3.3 ohms
Test B (thermopile): 530 mV
Test C (thermocouple): 27 mV
Test D (operator pull in): couldn't test because operator would not pull in
Test E (resistance system): did not test. I didn't think this was relevant because I can not even turn the knob to "On" without the pilot going out.

Thanks.

sounds like its time to call a vc/monesson dealer for a new valve...
i'd call the factory first to confirm, but sounds like a bad valve

i dont have much experience with honeywell valves