I have a Payne 90% gas furnace. It was installed in 1991 or 92. Ten days ago we woke up to no heat. I cycled the power to the unit and it fired right up. It maintained the heat cycle until the house reached the set temp. It worked OK for a day and then same thing no heat and would work fine after cycling the power. The White-Rogers programmable T-stat that was originally installed (and only displayed Celsius) was replaced as the suspected problem. What is a real concern is that once I had to cycle power several times to get to the point where the burners fired up. The igniter would glow and then I could hear a relay trip and then nothing. About the 4th try the burners kicked on and it ran. With the new Honeywell t-stat installed all was good for about a week. Now same issue has returned. As an aside, it seems to take longer to come up to temp then before. It took 2 hours to gain 4 degrees. Any suggestions would be welcome on how to troubl shoot this. Thanks