Help with Monessen VF gas unit

[tmy23]

Greetings. I have a monessen VF gas (NG) fireplace log set that won't hold a pilot. I have cleaned it up, and still no dice. I get good spark and the pilot ignites, but once I turn the control to "on" flame goes out. reading the manual it says either control or thermocouple. thermocouple is cheaper than the control so thought I'd go that route first. here's my confusion. Immediately above the gas tube there is a round, cylindrical metal "probe" which extends into the pilot flame. I thought this was the thermocouple. But there is also a small metal probe rising upwards into the pilot (not the igniter wire) which the manual says is the thermocouple? Are there two thermocouples? Should I replace both? AND...is there any way to test whether it's the thermocouples vs, the valve before I buy parts?

thanks!

 

[DAKSY]

Before you spend money on the thermocouple (TC), look closely at the pilot tube.
You will find a small (maybe 1/16" diameter) hole that is the Oxygen Depletion Sensor (ODS).
Make sure that hole is clear of dust & pet hair (if you have pets) & give it a try.
More often than not THAT is the issue with this type of product & the TC is fine,.
Replacing it will be a waste of money.

 

[Heatsource]

Bob is right, and i'm sorry not to be of more troubleshooting help, as we dont do any Vent free around here

 

[tmy23]

Thanks! will give it a try....

 

[Tech Guru]

Tried Compressed air, blown both into the side air mixing hole and even used to blast out the actual pilot nozzle. Saved many a customer an unnecessary part purchase with that tidbit of cleaning advice.

DO NOT DO THIS WHEN THE PILOT OR ANY OTHER FLAME IS PRESENT! Sorry, obligatory safety warning...