Volvo Repair: ABS Warning-Spedo failure, volvo v70xc, abs sensor

Question
Vedat,

I have a 1999 Volvo V70xc wagon.  I have what appears to be an electronics problem.  On an intermittent basis my ABS light, brake light abd transmition mode "W" light (the up arrow) come on.  a few seconds later the the speedometer fails.  This can go from anywhere 10 seconds to several minutes.  If I shift into the low gear,  It sometimes makes the ABS and brake light go off , though the arrow light will remain for several minutes.  Ocassionally if this happens when the car is at a stop light, the car does nor want to go forward.  It is as though the brakes are locked on.  If I shift into low gear this sometimes solves the problem....but not always.  In all cases if I turn the car off for a period it generally corrects itself.  The car can go for a day or a few hours before all of this happens.

I have done somesearching and I read that the ABS sensor and the wheel rotational sensor may cause all of these problems if they are dirty.  I have checked the tire pressure to make sure the wheels are rotation at the same velocity.  Another thing that I have run across is cleaning the ABS sensor plug.

Can you shed any light on this problem.  Every time I have gone to a dealer in the past they just want to fix the problem by swapping boards.  Most do very poor diagnostics.

Can you help?

Regards Richard

Answer
Hello,
according to your "clues" it seems to me this problem is "charging" problem, I mean your car's "alternator" has problem, when the alternator gets hot, it will be "stuck" and it can not charge the battery so you will face to face with this problem.
I recommend; firstly check your battery, the voltage level of the battery (when the engine stops) should be 12.5 Volts or more. Then start the engine and check the charge level of the alternator, it should be 13.5 Volts or more, but please be carefull, at the beginning you can take this value from the alternator, however leave the car for example 1 hour more (the engine will run in this time at idle, and our aim at this time to follow the alternator's behaviour while it gets hot, the alternator will "stuck" or not I mean while it gets hot, the alternator will continue to charge or not, in my opinion when it hot, it does not charge (you will take 12 Volts or less for alternator charging value) so you face to face with this problem)
Make these and write me again, good luck...
Regards...