The engine fan blower is loud while accelerating in 2006 chevy trailblazer

A jet engine type of noise from the engine area usually means the fan clutch is going bad. I don't think the tach is related to this, that could be the stepper motor for the tach going bad.

A belt driven fan? WOW! I thought these were all gone.Sounds like you may have a bad thermostatic fan clutch.Or,this crazy hot summer is making the clutch do what it's supposed to do(run the fan harder when it's hot out).My 99 Chevy work truck's fan will kick in harder on ocassion,but only when stuck in traffic on a hot day with the engine hot.If your fan runs likr this at all times,replace the fan clutch.(Get a good one,and they should ask if you have heavy duty cooling when looking up the part number.If the parts store doesn't ask,it might be a generic replacement,so be careful.

sure, no problem. Let me know if you have any trouble getting it done.

{: ) It's possible that you need to clean your throttle body for carbon build-up. Also check your air filter and spark plugs as well. Also have your engine cooling fan checked by mechanic for proper slack.

you have a vaccum leak, or a vaccum line came unhooked

My 2002 Chevy TrailBlazer sounded like a jet taking off...it was the clutch fan.

Check your coolant level, low coolant or air in your cooling system will make a "thud"noise in your heater core when the engine is under load from acceleration. The coolant rushes in to the heater core where the air pocket is trapped and then your hear the noise.
Start with the simple and make sure your coolant level is correct and then try to purge the system to remove the air out for your coolant system.
Thank you for using fixya and good luck

on the right side of the instrument panel right next to blower motor.

It is the bearing in the idler pully. about $35 and 30 minutes of work and its fixed.

This one is easy. The clutch fan is not disengaging. Mine does the same thing after it has idled a while but then will release (wind noise stops) after getting up to speed.