I am hearing several "thumping" noises in the ventilation when my GMT or GMTH is trying to start. The unit is roughly 6 years old and I have never had a problem with it until now.

It thumps maybe 7-10 times then it kicks on and starts working.

Thoughts?

Thanks.

Need EXACT model number

According to the faceplate the model # is: U36 Rev B

No cigar. Try looking behind the furnace door on the front of the furnace. In other words remove door and look for the furnace rate plate.