Problem with Heatilator NG fireplace

I have a Heatilator NG fireplace.
Model number GDCL36
Serial number GA426033

Was installed new in 1999 and worked fine until this fall when pilot would ignite, but not remain lit. Replaced the thermocouple which solved that problem, but now cannot get the burner to ignite. Electric wall switch turns burner on and off.

Any suggestions? Thanks in advance for your response.

Thank you for your timely response. I do not get any reading on the multimeter, which you indicate means the thermopile needs replaced. Is it possible to not have the thermopile set properly in relation to the pilot? I tried to reassemble it as it was when I replaced the themocouple. It appears the pilot flame is properly contacting the thermopile.

Assuming the thermopile needs replaced, do you have any suggestions on where to find one? I am in a rural area several miles from any dealers.

Thanks again for your help.

Will do. Thanks again, you have been very helpful.

Make sure the valve is in the "ON" postion. That's the simpliest solution, it's easy to have the valve knob in the wrong postion, where the pilot stays light, but burner doesn't light.

May also be you're switch. Removed the glass, light your pilot, make sure the valve is in the "ON" position. Next use a paper clip to jump the TH and THTP terminals on the valve. If it light, it's your wall switch (or wire).

Lastly, since you're on your way to replacing the TP anyway, try clipping off the wire leads and attaching them directly to the TP and THTP connections on your valve. Somethings those leads get a little crusty. It's odd not to get any reading.

Thanks for the responses. I thought I had solved my problem. I installed the new thermopile. Lit the pilot and the burner ignited. I turned it on and off a few times and then shut off the burner leaving the pilot on. Everything appeared to be working normal. About 4 hours later I triend to turn on the burner and got no results. Now I am more puzzled than ever. If anyone has futher input it would be greatly appreciated.