Fireplace will not stay lit

[MInnGas]

My 15 year old build in fireplace is giving me problems for the first time. Pilot stays lit but main flame goes out after a few minutes. I have cleaned everything including surface of thermocouple which I suspect.
Wiring seems good as I can jumper the ignition bypassing the switch and even that wont work when it shuts down. I'm open to suggestions but if it is the thermocouple is that something I can simply replace?
I see where it unscrews from the main assembly. I don't know what is inside a thermocouple or how it triggers the mechanism so I am leery of just taking it off. Please advise. Thank you.

 

[DAKSY]

My 15 year old build in fireplace is giving me problems for the first time. Pilot stays lit but main flame goes out after a few minutes. I have cleaned everything including surface of thermocouple which I suspect.
Wiring seems good as I can jumper the ignition bypassing the switch and even that wont work when it shuts down. I'm open to suggestions but if it is the thermocouple is that something I can simply replace?
I see where it unscrews from the main assembly. I don't know what is inside a thermocouple or how it triggers the mechanism so I am leery of just taking it off. Please advise. Thank you.

Can you give us the manufacturer & model of your unit? That & maybe a pic of the pilot assembly & the gas valve can be valuable. 15 years ago, the workings of these gas units were different than they are now, so every little bit of information you can provide will help us to help you.

 

[MInnGas]

Thank you. How's this?

 

[DAKSY]

Thank you. How's this?

Good job. In the center pic, the one with the pilot hood, there are two thermo-generators. The one on the right is obviously working, because that is the thermocouple which controls the gas flow to the pilot, That is the smaller of the two. The larger of the two, the one on the left, is the thermopile. It controls the gas flow to the burner. You should be able to get a universal millivolt generator (aka Thermopile) at a True Value or an Ace Hardware store, for about $50. Once you get that, if you can't figure out how to replace it, report back & one of us can talk you through the process. It's not too difficult.

 

[MInnGas]

Thank you. Not so easy to find around here. After running around all day I found one at a fireplace store but they wanted $69. I walked out and found one online for $35.
Is it important to plug the hole the wires come through with fire-stop or high temp silicone? I notice it was plugged before but brittle and I had to break it away to clear the old thermopile wire. Otherwise I got it apart. Not difficult but messy.

 

[Heatsource]

If it is a direct vent unit then yes, it is very important.
either way, seal the hole w/hi temp red silicone

 

[MInnGas]

That seems to have fixed it. I used the red silicone too.
Thanks a lot for the help. I really appreciate it. Now that I have it working again I intend to replace the switch with a thermostat.

 

[DAKSY]

That seems to have fixed it. I used the red silicone too.
Thanks a lot for the help. I really appreciate it. Now that I have it working again I intend to replace the switch with a thermostat.

Make sure it's a Millivolt T-Stat. For a nicer option, take a look at the Skytech remotes. You may never leave your recliner...

 

[MInnGas]

How could I not have known about remote thermos! I would have bought one years ago. I just placed an order. Thanks again