When a furnace is replaced with a newer style unit like yours with an inducer motor, they sometimes use the old vent pipe. These old style vent pipes are transite (light weight cement), the moisture created from your furnace exhaust is caught on the cool transite surface and runs back down into the blower blades or wheel bringing a white mineral deposit with it which causes your problem. The vent should nave been replaced with the heater using a metal vent material. You will need to replace your inducer motor assembly and vent pipe to prevent a recurrence.
Just replace a similar draft inducer Fasco item and the problem with the old one was the blower wheel had slid down the motor shaft and was rubbing on the housing. I was also able to get my old blower going but "pushing in" the motor shaft. This allowed the motor to spin up the wheel and function till the next cycle. Also, a clue that this is a problem is the "thumping" noise from the furnace when it cycles on. New unit is so quiet I can't tell if the furnace is on!
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Had what seemed to be similar problem
Check drain tube coming off fan. Stopped fan noice when water drained and allowed burner to run. Presure sensor was fuled by the trapped water. I cleared drain tube of clog and reattched tube. Problem solved.
billriii
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