1991c4

Sorry new to rennlist and porsche ownership.. I have a 91 c4 and was driving it the other day started her up and the diff warning light was on and seemed like the diff was locked. restarted and no change so started to move and was like I was hopping..

restarted again and everything went normal and no issues for the rest of the day. had the car for a few months and no issues before and just that one time.

any ideas?

crg53

Hi and welcome onboard, can't help you with the light issue, but where are the pictures...........

altarchsa

Rocket Rob

Verify that the brake fluid reservoir is full. I've found that you can get 4WD errors if its not right up to the max line.

tbennett017

Also it might be a good idea to bleed the diff locks - They might be sticky? Search here for the procedure. It is like bleeding the brakes but a bit more complicated.

Rocket Rob

By the way, did anyone tell you that we expect pictures of your car when you join?

tgage

The locks were not disengaging as the hoping you were experiencing was the car in its "I can get out of snow mode". I suspect you went above 5 mph which is suppose to automatically disengage the locks. My recollection is that once a fault is thrown, you need the scan tool (or other work-around to clear the fault... I use Durametric's tool, but most hear use a home-made version... search under scantool). The fact that it was locked indicates something is wrong, and the above advise is good for a start. I believe there is a DIY for bleeding the C4 in the DIY section, but just speak up if you need advise.

tom

ian89C4

Check to make sure you have the correct tire size. Wrong size and it throws off the sensors.

1991c4

Thank you all. Running cup 1 replicas.
I could not fine bleeding the c4 diff. Saw brake bleed.

Rocket Rob

This is the set of threads that I found on bleeding the PDAS.

https://rennlist.com/forums/964-1989...e-of-cake.html
https://rennlist.com/forums/964-foru...placement.html
https://rennlist.com/forums/964-foru...-problems.html
https://rennlist.com/forums/964-foru...-bleeding.html

I hope this helps.

drjsuh

There are some really good posts in the tech areas section on our AWD systems. I had a similar issue the other week and it seems that it was just a low battery level. Since I stopped leaving my iPOD pluggedin overnight, the diff/pdas warning light goes out after 15-30 seconds (i.e. normal) on first start up and goes out immediately thereafter for the rest of the day.

1991c4

Well figured it out. It was actually the clock. I had replaced it because prev owner had a spare so I tried that one because the light was out in mine and wham. Replaced back to the original and no issues