Dual-zone HVAC rattling loud. Request help.
 

Good day!

I have an '07 Monte LT (32K miles) with the factory dual-zone climate control system. Within the past three days, the system has begun rattling loudly. A rapid RATTATTATTATTATTATTATTATTATTAT sound coming from the dash behind the HVAC controls, like someone rapidly and rhythmically tapping the lower dash with the handle of a screwdriver. Loud!! Annoying!

It will happen with any large adjustment of the HVAC settings, such as moving one of the temp settings off of hard cold (for summer) into the warm (for fall). Once the rattling starts, it won't matter which vents I set the air to come out of, whether or not the fan is running, whether I have it on "fresh" air or "recirculate", etc.

I work in the automotive business on the sales side, and a different '07 Monte LT that we had in our pre-owned sales stock at the time had the EXACT same issue and noise. Off it went to the Chevy dealer for a fix under warranty, but that was three years ago and I -cannot- remember what their diagnosis was nor which part failed.

Your theories, please? How much does the repair typically cost?

-M

Actuator gear teeth have broken off.
 

The gear teeth inside one or more your actuators have broken off.That's the "ratta-tatt" sound you hear. I have replaced dozens of these. Good luck.