Carrier Furnace code 33 @ startup blower fan sounds like jet
 

Carrier Weathmaker 8000 High E 2 speed Gas Furnace Model 58TUA08014 S/N 2097A08940 (80 BTU high 52 low) installed 1997? .. new 15 seer AC added 3 yrs ago; last service maintenance 2 yrs ago

Problem.. at heat start up fan noise similar to jet engine starting up but noise disappears within 10 seconds. In last few months, this jet noise seems a bit louder than usual, but still not really bad. At first thought common to blower motor. Then 3 days ago Honeywell Thermostat message AC /Hold. Noted furnace blinking code 33… Limit or Flame Roll-out (FRB) switch is open FRS switch requires manual reset..Check for: inadequate combustion air supply – FRS switch only; dirty filter or restricted air supply; defective switch or connection; blower motor or capacitor failure; Code disappeared in about 3 hours; has now happened a second time. turned power off and checked cycle nothing out of ordinary and no excessive noise at furnace

My thinking it's a blower motor /fan problem? Any insight ???
Concerns… guessing fan motor may need to be replaced but before calling HVAC Tech want to understand what technician should check and other causes/ problems?

If blower/fan what is typical replacement cost be for part? for labour? normal time required as in more than 1hour ?

Appreciate furnaces can last 20 yrs (mine approx 13). What' typical best price I might expect to pay to replace furnace? Any tips on for homeowners in considering replacing unit vs repair?

Thanks for comment

Before going to the expensive possibilities, have you checked/replaced the filter?

This may not be related but may be worth checking out.
It may not be the main blower motor that you are hearing. If this is a forced vented model it may have an inducer? motor. Mine has one and it provides airflow through the exhaust vent piping (PVC) when it's firing the burner. It has a little bit of a jet engine sound and you can see the impeller spinning with the front furnace cover off. Try looking on the front cover or service manual to see if there is a diagnostic test you can run. My furnace will run a diagnostic that tests both fans, the hot surface ignitor and a few others I can't remember right now. This may help narrow it down.

Steve

Fan noise
 

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This sounds like the inducer fan motor is failing. Given the age, it wouldn't be too surprising. Also check the combustion air intake as well as the discharge line for any obstructions, damge, etc.

These motors cost around $160-$180 and are easy to change.

thanks McSteve.. yes replace filter regulary and recently too

thanks for input, will definitely check out inducer fan motor. Have checked for obstructions, none noted

thanks...