I have a carrier furnace. Recently, when the blower ran and no heat came out, I replaced the ignitor and that fixed the problem. Now, two weeks later it is happening again.

I've owned the home and furnace for 16 years. Have replaced about 10 ignitors and three PC boards.

Is something else causing these problems?

Did you touch the glowing part of the ignitor during install? This is the black dark grey part of the ignitor.