wgerola

I know this has been done to death, but does anyone know where to buy an accelerometer, otherwise known as the 'lateral acceleration sensor', part number 993.606.153.00 (besides the dealer)?

The dismantlers I have called do not have the part. The dealer wants $2180!!!

As a side question, should I even bother fixing this issue? The one for the ABS is working, this is the important one. The one for the rear diff isn't working. All it does is lock the diff during a corner. In the absense of this accelerometer, the differential is open, acting like a Carrera 2 with an open diff, or without the LSD.

Since this will be asked, "why don't I just clean the accelerometer?", I have tried and does not fix the problem. One of my accelerometers is the older style mechanical unit, and the other is the newer style. I have put the newer style (and more reliable) into the ABS unit since it's more important.

colo964

Try switching their places and make sure the old one's pendulum is centered before reinstalling it. I seem to remember having that same problem a few years back. Saved me $300 for a dumb part.

aeroman

So what you are telling me is if I disconnect my accelerometer for the rear diff that I will still have AWD but with the float of a C2? Or is that just as bad as unplugging the control logic?

wgerola

I have very carefully read Adrian Streather's 'Technical overview of the Carrera 4 AWD and Traction control system (PDAS) and all 964s ABS system' (http://www.adrianstreather.com/docs/...overviewR2.pdf) and if I am correct in my understanding:

The longitudinal accelerometer controls the ABS and PDAS (the PDAS being the 4wd system which is engaged in a low traction situation). If this unit works, the ABS works and the system can distribute traction to the front wheels. The PDAS system controls the center differential, which distributes power to the front wheels.

The lateral accelerometer controls only the rear differential, which will lock the diff (at speeds above 19mph/30kph) when it detects that you are in a corner. This locked rear diff is what induces understeer, reducing the oversteering tendancy in 911s.

Therefore, if I'm interpreting correctly, then if you have the longitudinal accelerometer working correctly, you're in good shape. The ABS works and the 4wd system works as far as providing traction. If the lateral accelerometer doesn't work, then your rear diff acts like an open differential, since it only locks if the accelerometer is working properly and indicates a hard turn.

Just to complete the picture, if the longitudinal accelerometer is not working, the ABS still works, but the center diff will not be activated by the system, so the 4wd will not work.

Does this make sense to everyone? Is this right?

Lastly, in my investigation of accelerometers, it seems that the older style accelerometers are mechanical, these are the ones that have the swinging pendulum and can sometimes be cleaned. The newer accelerometers (993.606.153.00) do not seem to have any moving parts and are all electronic. These do not seem to fail.

Is this correct?

Sorry guys, but no one has the definitive answer on these things, so I think it may be worth reviewing the whole thing once and for all. Thanks.

aeroman

By center diff you mean the front tires will not pull at all and the rear will act like a C2?