Mechanics

VOLKSWAGEN CABRIOLET INSTRUMENT CLUSTER PROBLEM

1992 Volkswagen Cabriolet • 140,000 miles

RPMs dont work I changed instrumen cluster what else could it be besides wiring problems?
Avatar
Agust1989
October 23, 2012.



1) You changed the instrument cluster because the rpms were not working

or

2) the rpms don't work after changing the instrument cluster

There is a difference, just need to make sure I know the whole story.

Thomas


Tiny
Exovcds
Oct 24, 2012.
I changed the instrument cluster because the RPMs were not working, and still not working.


Tiny
Agust1989
Oct 24, 2012.
Is your fuel injection system Digifant (Electronic Fuel Injection). It should be, but some countries
still used a version of CIS or even a Carburetor.

I doubt it's a diesel, but if it is, the diesel tach gets its signal from the alternator (look for a broken
wire (red/black if I remember correctly).

Once I know the system, I can look for a wiring diagram and then you can do some pin testing.

Thomas


Tiny
Exovcds
Oct 24, 2012.
Using a test light, you can trace the "tach wire" to the instrument cluster and see where the "blinking"
stops. Remove the instrument cluster and start the engine. Using the test light (attach it to a clean
body ground, and test the light in the cigarette lighter to make sure the light works) and touch it to
the disconnected instrument cluster harness plug. One pin at a time.

The one pin that causes the light to blink rapidly, is the Tach wire. If the light flashes, but you have
no tach operation (is everything else working correctly?), Then you might have a bad circuit board
in the instrument cluster (the one that controls the oil pressure warning buzzer, it uses the tach
signal to determine when to trigger the buzzer).

If none cause the light to blink (rapid flashing the faster the engine is reved), then go to the Ignition
Coil under the hood and check that the Ignition Coil has wires attached to both sides (look for the
red/blk wire, that should be the tach signal wire).

Touch the test light to the red/blk wire and confirm that it is flashing / pulsing (engine running).

Once you have confirmed that the wire is attached and that you have a signal there, follow the wire to
the rear of the fuse box / relay panel. The wiring diagram I have, shows the wire going to the back of the
relay panel at plug G1 pin 12.

Following the wires will be a bit of a pain, but the only way to confirm when / where the signal is lost.

Still looking for a correct wiring diagram that will be of help.

Thomas


Tiny
Exovcds
Oct 24, 2012.