Before we check the BCS. we have to look at another issue. From your post, you describe your operation as backwards.

With the car OFF, the arm should be all the way down, with the BCA extended.
At IDLE, the arm should be all the way UP with the BCA retracted.
When you rev in park or neutral, it SHOULD NOT MOVE. The PCM should be in bypass.
When you pull the TOP vacuum line off the BCA, it should EXTEND, pushing the arm DOWN.

Verify your vacuum connections:

Attachment 57207

https://i14.photobucket.com/albums/a...lwren/bca2.jpg

Attachment 57208

The routing should be obvious with the red lines you see here. Ignore the unused port on the BCA (that's for a vacuum-relief vent, and most of our foam filters deteriorated long ago).

AFTER we figure out why yours is acting funny, you'll want to go back to the rear of the engine to check your connections (vacuum and electrical) to the MAP sensor. The MAP is a rectangular box on a bracket just behind the #4 fuel injector (between the SC and firewall, above the rear valve cover). Small box. One vacuum line, one electrical connector.

Do the carb cleaner test on this one too (at idle).

Man, thanks for such detailed help!

When the car is off, the BCA is extended like you said.
When idling, the BCA is retracted as well.

BUT, when I rev it in park, it extends/retracts.....

When I remove the top line, it DOES extend like you said.

My hose connections do not look quite like yours. Out of the BCS the line goes toward the front of the charger to a small round silver thing at a tee fitting, the other line off the tee goes under the charger nose to another tee.

I'm going to get a digital camera today and get photos of the routing, etc.

Excellent. That supercharger ever been off the car that you know of?

Whoops, I just noticed something.... he has a 98, therefore a S2. Isn't the vac line setup dramatically different?

It does look WAY different than the pics Willwren posted. As far as I know, the charger has never been off. It had 125,000 miles on it when I bought it.

So you're saying the BCA should NOT move when I rev it in park?

My goof. I was fixated on the older cars in your sig.

Check the TEE fitting under the nosedrive of the SC. Can someone please post pics of the S2 routing?

Sorry that its freaking huge.

https://www.autozone.com/images/cds/...3d8015e545.gif

That's mine, and it's hooked up correctly. Now I know the "small round silver thing" is the fuel press. regulator... :oops:

While using a mechanical gauge is good for many tests, the general feeling of the car should tell the poster if they have boost or not.