Lately I notice the ABS light when starting and driving away, after a few miles it goes off. What can cause this ? bad earth maybe ?

 

I've had similar problems with my ABS light... used to flick on and off when hitting bumps in the highway. Once, it came on right after startup (and the alarm buzzer sounded) but went off almost immediately. I tried various solutions but the one that seems to work is to remove the ABS relay and pry the contacts open just a little. (the relay seemed loose in the socket) This seemed to work; no flickering ABS light for some weeks now.

 

Great suggestion. My 964 has been doing the same thing. I figured it was something loose, but a relay is an easy fix to try out.

 

Speed sensor gunked up with crud? Does it happen at the same speed or does it vary?

 

Mine used to do it for no apparant reason and would stay on with the buzzer sounding until cancelled with the switch.
The ABS functioned OK and I checked out and cleaned everything that I thought was connected with it which made no difference.
This persisted for over a year so in the end I disconnected the buzzer by pulling the plug off, thinking I'd put up with the light coming on and not be startled when the buzzer sounded.
That was last summer and the ABS light has not come on while driving since. All the warning light functions work OK, just without the warning buzzer.
Anyone explain why it would appear to have fixed the problem?

 

It could be the same as my ABS lamp problem ...

Sometimes when I start the car, the battery lamp is not illuminated. This normally should kick start the alternator to push charge back to the battery. As it doesn't light, the battery serves all the cars electronics needs. The load from this is enough to pull the battery output low. If your ABS sees a low voltage the lamp comes on.

So if your problem is the same as mine - you get an ABS lamp light until you either rev to about 3k rpm and then it goes. Before I found this out (and because I start off sloooow), the car has ran out of battery juice before I've realised this and then you are in real trouble as the battery is real flat.

I've checked my battery lamp and its fine. I've checked the electrics inside the clock and they are fine - I must have a poor joint in the loom or a bad alternator. For me, it might have crept in when I had a scuttle repair last year... Sometimes is lights other times it doesn't. Normally warm car = lamp on.

So - simple checks:
Is battery lamp illuminated when you turn the ignition on?
Do you see about ~12V when the ABS lamp lights up?
Does it go off if you Rev to about 3k?

If it is the same problem as mine, don't overlook the simple battery lamp check.

Cheers, Lee

 

I had this when I first bought mine. A new battery cured it for me. Just the light on its own tends to be down to problematic electrics - battery, bad earth or charging. It seems to be only when you get the buzzer too that it's a real problem with the ABS circuit.

 

As Lee mentioned the electrics inside the clock already, check if the ABS light goes off when you exceed about 2800-3000 rpm after starting your car. If this is the case, it could be the well-known issue of cold solder joints on the back of the clock. This fault might cause additional problems with the airbag warning light staying on etc.

Just have a try after starting your car and search the forum for this topic. You should also find the solution for the clock repair on Johns 964 webpage: www.porsche964.co.uk in chapter "technical/electrical repairs".

bernd