Rheem Criterion lights, but only runs for 30 seconds max...
Rheem Criterion blower starts up, runs for about 30 seconds until the HSI starts to glow, it ignites and all is fine for about 30 - 50 seconds. Then, it all shuts down with the exception of the blower.
Now, we had the heat exchange replaced last year b/c it was cracked, and while looking at the pressure switch I noticed something. Where they connected the new HX to the exhaust pipe there is a slight gap at the bottom where the "thermal tape" doesn't quite meet up. It seems to be about one inch long and about an 1/8 -1/16 inch wide.
Would that gap cause the pressure switch problem?
Here is a picture...sorry about the blurriness, but you can hopefully still see the gap.
That is on the downstream of the fan and should be sealed properly so no flue gases enter the house. Won't cause your problem. Rheems have had quite a few pressure switch failure problems on some of the mid efficiency units. You may want to get a pro to check it.