Gas fireplace won't light

I have an Earth Stove TG440. It's a gas stove/room heater with artificial logs. The pilot lights fine. When flipping the on/off switch to on, the stove burners don't come on. I had this problem last year and had a furnace repairman in to fix it. It worked fine right after that. Now this winter it doesn't work again. So I figured I'd troubleshoot it myself before calling the repairman.
The troubleshooting guide says to short across the switch to see if it is a faulty switch. If that doesn't work, then short across the contacts at the gas valve to see if it is faulty wiring from the switch to the valve. I couldn't figure out how to easily get to the underside of the switch, so started by shorting across the contacts on the valve. There was a click, and then the burners lit! I proceeded to disconnect the wires to the switch and hook up two wires to a thermostat that was originally installed by the stove dealer, then later disconnected. The thermostat didn't cause the burners to light. No click, no nothing. So I disconnected the wires from the back of the thermostat and shorted them. I can hear the click like the gas is going to come on but then the pilot promptly goes out. It doesn't look like it's being blown out. It looks more like the gas to the pilot is just cutting out. Shorting directly across the contacts on the valve is now doing the same thing. Click, then the pilot goes out. The burners only lit the one time earlier when I shorted across the contacts on the valve. Now just click, and the pilot goes out.
I tried adjusting the pilot screw to increasing the gas to the pilot a little bit. Didn't help. The pilot sweeps over one side of thermopile, on about the top 3/8 to inch. It doesn't engulf it though, just sweeps over one side. One diagram in the manual shows the flame sweeping over just like it is physically doing. Another diagram shows the flame engulfing the top 3/8 inch or so of the thermopile. I don't have a voltmeter or would check the millivolts from the thermopile. I may borrow or buy a voltmeter to check this. I'm thinking maybe low millivolts from the thermopile since neither the switch nor the thermostat produces a click (valve on) but shorting the wires does. The low voltage from the thermopile may not be able to overcome the added resistance of the contacts in the switch or thermostat. The manual says the thermopile should read 125 millivolts with the on/off shitch off, or 250 millivolts if an optional themostat is utilized.
There is also a ventilation safety switch in the circuit. The troubleshooting guide indicates that if the vent is obstructed, by birds nests for example, the burners will light but then go out after a short time. Mine burners aren't lighting at all though.
Any thoughts on the cause of the pilot cutting out when I switch on the gas to the burners?
Thanks, Paul S.
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A couple..maybe three now..LOL

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CBHVAC wrote:

Hi, Interlock switch? Tony
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..................<sipped all that scientific, time consuming, thinking about buying new tools to work on it, troubleshooting stuff> ==Dust. Get a can of compressed air and blow it out. Hope the furnace repairman didn't charge you too much last year. ==
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Blow out around the gas valve, and around the pilot and thermopile? Anywhere else?
Paul
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wrote:

==No. That should do it.
Check page 19 of this manual (it's a pdf file, meaning it's large) for dust cleaning instructions.
http://www.comfortglow.com/bayfront / ==
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responding to http://www.homeownershub.com/maintenance/gas-fireplace-won-t-light-72403-.htm diver8718 wrote:
Paul Stivers wrote:

--
Did that work paul? I have the same heater Earth Stove TG440 .
went to start the pilot wouldn't stay lit ? so I replaced the
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I'm pretty sure Paul fell asleep, diver. He had that trouble back in December of '05, and he just couldn't stay awake long enough for you to come along and ask him about it.
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-snip-

Amen. I bought a new thermocouple the first year I had my gas logs. The next year I found out about the 'duster in a can'. Works great!
I think gas logs are dust magnets.
Jim
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wrote:

==Yep--I'm guessing it has something to do with the airflow. BTW, for the folks who may not be aware, a yellow tipped flame is an indicator of dust as well. ====
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