SaabCentral Forums banner

1 - 2 of 2 Posts

·
Registered
Joined
·
387 Posts
Discussion Starter #1
My 2003 Aero has a problem in the HVAC system. Any time vacuum drops, such as when I shut the engine off or when I open the throttle significantly, it makes a loud tap, like a big acorn has just hit the windshield. It does it about ten times then the vents blow tepid, humid air for a short period.

I have used the search function and there are similar problems but nothing exactly like this. It's loud and scared the wife the first time she was in the car. :lol:
 

·
Registered
Joined
·
1,319 Posts
Intriguing. Checking the system overview, I can't see any connection between engine vac and HVAC behaviour.

The multiple taps makes me think of the hexagonal drive shafts on the stepper motors, and the matched sockets they plug into on the blend flaps. The sockets develop cracks, so when flap reaches full travel, the motor is still able to turn, as the socket splays open a little. Since the motor still turns, it doesn't experience the physical resistance (> current draw) it should when the flap reaches full travel, so the command from the ACC panel is to keep going.

I guess it goes 10 clicks and gives up.

I would take the kick panels off in the footwells and observe the pushrods/white cranks while you replicate what causes the phenomenon.

Doug
 
1 - 2 of 2 Posts
Top