Thermopile or gas valve

[weakfish]

I have a Heatilator GNRC36 that won't light when wall switch is flipped.
The static millivolts are 337, flip the switch and they drop to 186. Tap the valve with back of screwdriver and the valve opens. Question is is the voltage too low or the valve bad?

[hearthman]

Weakfish, we cannot get into technical aspects of troubleshooting very far in this forum. If you want in depth discussion, we can ask a Mod to move it to the Pro forums. The problem is, not too many Pros are familiar with these systems. Let us know how you want to procede. I can PM you some info. if need be.

Hearthman

[darthvader]

First the millivolts are too low, typically you wanna see 500 or so depending on the pilot flame. Second the valve is probably sticking a little bit. Third you may just have a bad connection in the switch circuit cause the drop in millivolts. also when you stick the screw driver in to tap the valve you could be bumping the wires enough to over come the bad connection.

[ZeroTolerance]

I would assume that if you are "tapping" the valve and it is opening it is a mechanical issue. As for the thermopile they range in MV so I couldn't tell you how many MV's you need to open the valve without the model number off the valve.

[Makinhole]

Millivolts are to low. How many millivolts do you have through the switch circuit? Clean the pilot and replace the thermopile. I always clean every connection, both the wire and the point of contact. If you were going to replace the gas valve you would clean the pilot and replace the thermopile anyways...I would not advise "tapping" on the valve, tends to lead to the get a bigger hammer scenario....

[weakfish]

Thanks to everyone for replying. After taking a better look, it was a small pilot flame. I should have seen that the first time, but the pilot is in the back under the logs, a quick peek under the logset looked like a big blue flame on the burner and termocouple side, but after removing the logs the flame on the thermopile side was weak. Cleaned orifice and millivolts jumped up to 530 My bad Thanks again