Robert Shaw 7000 fireplace odd issue

MasterGasMan

Servicing an old fireplace that had one of the old RS7000 series green knob valves; thermopile only system. Those old green knob valves had a service bulletin and some recalled many years ago so nearly everyone i see now needs to be replaced for excessive venting, bad valve knob spring and bad electronics.

Now, Ive been doing this 26 years and Ive never had a problem like this. I always replace the valve and pilot together on these units. Those old large compression pilot tubes tend to leak if not replaced. Anyway, did the pilot and valve, pilot would light, but millivolt would climb slow which isn’t terribly unusual. Turn main burner on, would run a minute then everything would cut off. Figured bad thermopile or bad valve. Long story short, 3 valves and three thermopiles later and same problem. The old thermodisk/snapdisk has been bypassed as they almost always are on these old units so thermopile is direct to valve. Tried with wall switch and without with 1001a remote in case the wire was pinched in the wall.

No other electronics in the unit, venting good and not ghosting; does it with or without glass. There’s no way in hell i put on 3 bad valves or pilots. I even tried a dexen exact replacement incase i got a batch of bad RS valves. LP pressure normal. All 3 valve voltages were within normal limits. I do these replacements damn near everyday and in 26 years I’ve never run into this before. I found an old post on here from 2007 where a guy was having the same problem and it was never resolved.

While at the customers house i could hear mice in the wall. Is it possible mice ate a wire and the fireplace is grounding out? Short of demonic possession Im stumped. Im the guy everyone usually calls for advice and i dont like to give up so any thoughts would help. I even used the other parts i tried on other jobs so i know it wasn’t the parts. I spent about six hours on this job and told the customer im not charging them till i can figure this out. I’ve seen thermopile systems have problems, but nothing like this. Im strongly considering fabricating a new pilot bracket and just putting a two lead tpile/tcouple system in instead.