ABS, Brake & PDAS problem with a difference...
 

Hi folks,
I’ve been a bystander here for a time, while enjoyng the pleasure and paranoia of owning my second 964!

My ‘menoporsche’ is a 1990 C4 manual coupe. (my 1st a C2 Targa)

I should like some help/advice please?

My car is suffering from the well documented pdas, abs brake warning light problem, but with a difference…

When I put the key in the ignition the hydraulic pump kicks in and humms for about 40 seconds (pretty standard). When I start the car, the pdas, abs, brake and central warning lights all come on. (these are the only warning lights which remain on)
Now, If I blip the throttle and rev the engine to about 2500 rpm, the abs light goes out, but the pdas and brake warning lights stay on and start to blink on and off at 5 second intervals. At this point the rear spoiler light on the clock also comes on!
The car is permanently hooked up to a battery conditioner when in the garage. Prior to starting, the charge across the terminals is 13.85v. When the car is started (having disconnected the charger) this goes down to 12.5v. But when I blip the throttle the charge across the terminals goes up to 14.95 and holds, with the car ticking over.

I’ve tried a new abs relay, as well as checking and cleaning all the earth/ground points. Checked the brake fluid (when the engine is running) No change. There is no sign of any leaking fluid.

I’ve ‘googled’ and trawled thru the forums, but cannot find a thread which matches my cars symptoms.

I wanted to try and sort/diagnose this myself before going down the potentially long/costly trip to a Porsche specialist. I’d like to get the old girl 100% and enjoy a bit before this years excursion to the LM Classic.

So any thoughts would be much appreciated and gentle please as I do not profess to be a technical wizard!
If I've missed a relevant post kindly steer me in the right direction.

Thanks in advance, Rory

These are classic symptoms of the "dry joints in the clock" syndrome. I would put money on resoldering the joints on the inside of the clock PCB will solve all the problems.

Regards

Dave

Hi Dave and thanks for your response.
I never thought for a moment that the clock could be the problem!
Will give that a go as the next step,

Regards, Rory