Well I thought older units did not have a stainless steel cover.I could be wrong time flys by fast in the heating buisness.Maybe it was longer ago than that.I was only trying to added to the posible problems that the furnace may have had,not trying to say this was the answer.sounds like a lot of good techs in here.
I have a code 31 on my furnace. It starts then stops after several seconds. This is not a pressure switch related issue. The pressure switch it not open when the unit fails. I even held it in manually for a few minutes and the unit still starts and stops on its own. Any Advice?
K it ended up being the control pcb. I got one on ebay for $55. They have many more available if anyone else gets the same problem.
EVERYONE HERE HAS BEEN TALKING ABOUT THE PRESSURE SWITCH RELATED ISSUES. Watch the pressure switch to see if it deactivates before the unit fails. If the pressure swich cuts off AFTER AND NOT BEFORE the fan, furnace, etc cuts off, there is really no other components I see that can cause this problem other than the pcb. It fixed my problem!