holly furnace

[fireman]

I've changed pilot tubing, control valve,and thermalcoupling. Yet,I'm still having trouble with this old hag. After tring two control valves to get the pilot to stay lite, and now after the unit go thru its cycle-during the cool down thepilot go out 5 out of 8 times.What is my problem?

A check was done on the tranformer and it is good.

[DPSwitch]

Sounds like a hole in the exchanger blowing out the pilot or pushing the pilot flame away from the thermocouple.