tab a

IIRC my CC worked once, when I got the car a couple years ago, but not since. Looking into it now, servo and reservoir hold vac fine. When I bridge 3 to 5 and 7 to 12 on the brain plug, it barely moves the throttle, instead of moving it to 'full load' like the book says it should. However, I did find that if I open the throttle a bit, then bridge the brain, the servo moves the cable/lever up to where the throttle is, and if I let the throttle go, the servo will hold it there.

I'm not sure if all this means the servo is 'weak' (if that's even possible), throttle movement is too hard (possible?), or maybe it's ok, and there's really a problem with the brain causing it to not work on the road.

Any ideas?

Thanks.
Thon
'85S

gazfish

Hi, first thing I’d do is remove the actuator cable from the servo and see if it’s binding. If it’s not been used in a long time it could be rusted inside.
Do you see a continuous drop in vacuum when you operate it? You won’t know if there’s a vacuum leak in the airbag until the internal solenoid valve opens and it’s in a fixed position.
If you’re bored I pulled my apart to see what was going on a couple of years ago:

tab a

I had already found your video , and learned some things. Thanks.
Figured out how to get the cable out of the servo, and it looks pristine in there. Activating the servo drops the vacuum a bit but it then holds steady so I don't think any leaks there.
As I mentioned, if I open the throttle a little by hand, then activate the servo, it will hold the throttle in position. Moving the throttle by hand doesn't seem as smooth or easy as I would have expected, but I don't know what's 'normal'. I did lube it, without much change.
I'm leaning towards thinking the servo is OK and the problem is the brain.

928NOOBIE

The brains are common failure on these cars. I got a rebuilt one from 928SRus and it works perfectly.

gazfish

Yeah but, if you’re bridging the plug as per the WSM then the brain isn't involved, you’re putting battery power directly to the servo. The servo has a pretty strong pull with full vacuum so I’d be surprised if a stiff throttle can stop it. Not sure what else it could be though.