mtb968

I thought I read in the manual that getting all wheels off the ground will cause the roll hoop deployment. Go find a hump or bridge and have some fun! You can reset them by using a tool and pushing them down.

Kims996Cab

OK, since I like to understand my car, all this speculation (including my own) prompted me to go out to the garage, get down the service manual, and look it up.

At least for the MY2000 (and probably all other 996s):

From Pages 69-29 & 30 - Diagnostics:

The control module, attached behind the rear seat, consists of an itegrated g sensor and level sensors. The g sensor detects loss of contact with the road surface. The two level sensors detect vehicle inclination and transverse and longitudinal acceleration.

Capacitors provide reserve power in case of battery failure.

If the sensors detect a roll-over situation, the roll over bars are extended through spring force. A compression spring is located under each vertical shaft of each roll-over bar .... total of 4 springs.

For you real tech heads:

The level sensor consists of a spirit bubble (carpenter's level), an LED, and a photo transistor. Exceeding set limits of acceleration in either axis, or exceeding roll limit about the longitudinal axis .... causes the air bubble to pass through the LED light beam and be detected by the receiver.

The G sensor consists of a magentized weight compressing a spring below. In the event of sufficient negative G force, the weight becomes ligher and the spring presses it upward, making electrical contact to trigger the spring release in the roll-bar units.

Manual Triggering:

The roll-bars may be intentionally triggered by the diagnostic module (PST2), or manually by inserting a screwdriver in a sealed hole in the control module to press against a release pawl.

Instruction for re-stowing the roll-bars is found in the owners' manual. Required tool is included in the Cab tool kit.

CarlosR

Hi Bob,

Good to hear from you on this board. Been many years since we last chatted...

Just wanted to say that I'm pretty sure your statement above is not correct, or at least not for a '99 cab, which is what I have.

When I first got my car, I went out for an aggressive drive on a country road that I had driven a few times before. This time I was going faster, and when I went up over the crest of a small but steep hill, all four wheels left the ground, and a sudden loud BANG scared the crap out of me. At first I thought someone had shot at me (seriously, it was that loud), then I thought that I had somehow blown up the engine. I immediately stopped the car, and only then realized that both of the pop-up bars had deployed. It turns out that on my car, (and I suspect most other Porsches), the bars are just fired by big whopper springs, that sit there coiled up waiting to scare the s**t out of you. After the pop-ups deploy, the can be pushed down with a little effort and a long tool of some kind. So no pyrotechnics, but it sounded like there was!

Keep the shiny side up,

=Carlos=