I found a '90 C4 that evrything looks ok, except when I turn the diff lock in center console, nothing happend. Is there any warning light or anything to indicate that it's locked? How do I know if a 964C4's AWD system is working properly? Also, what's the orange light in the right upper corner of oil pressure meter that shows an "AWD" graphic?
BTW, the ABS warning light keeps on and off and beeping during the drive. The owner said he just changed soem compenent in teh ABS system (don't remember waht, maybe the pump or something) What's the problem?

Thanks!

 

Patrick,
When you engage the console button, a small yellow light next to the switch should start f lashing . Once you reach speed(? 40kmph) it should go off. If the PDAS( All wheel drive) is inoperative a warning light should light up in the clock(unless the bulb is out or has been removed). You can tell that the system is working because of the noise it makes during operation. Hope this helps. HSB

 

Thanks HSB.
I didn't see the small LED lit up when I turn the ****. How do I know if it's just the LED problem or the lock is not working? Also, can I assume the AWD system is working fine if I didn't see the orang light in the dash panel?
Since I never drove a normal C4 before (I did drive one with faulty PDAS control unit), is there any way to tell it's normal or not?

 

When you turn the switch to lock the diffs, there should be an audible "clunk" as well as the yellow led flashing. If the led doesn't flash, and you don't hear this - I'd say it isn't working.

 

Dear Patrik,
If the C4 moves the AWD is working it is mechanical. The PDAS or traction control system is different.
This C4 has a problem and I would not purchase it until it has been fixed.
Ciao,
Adrian
964C4

 

Dear Adrian,

From your article of C4 PDAS/ABS system, seems that if there is any trouble of either ABS or PDAS, both warning lights will on. Is it possible to have only ABS and master warning lights on but not PDAS?
Thanks!

 

Dear Patrick,
Yes it is but not for long. ABS only means that a specific ABS system failure has been logged. The PDAS will fail only when required to work under these circumstances. Works in reverse as well. PDAS for a while then ABS. Can be from 30 seconds to 30 minutes or evenlonger depending upon circumstances. However this is quite rare. Most common is that the PDAS warn light is removed.
You must not purchase a C4 with these problems unless the purchase price is discounted heavily and I mean heavily.
Ciao,
Adrian
964C4