Dash Instrument Lighting Fault

Hi,
When I put the headlights or sidelights on my rev counter stops working as does the MFA. Also the instrument binnacle does not light up. I suspect an earthing problem but I am not sure where to look. I checked the wiring at the headlights all connections were good. Any pointers would be great. Cheers.

look on the side of the head for loose or damaged brown/white wire

Grounds, or Earthing issues are quite common to the MK1's.  I suggest that you REPLACE, not repair, clean or refurbish your connectors, but REPLACE with 2 off the shelf battery cables from your favorite Auto Parts Places.
That is from the Battery to the Frame, and frame to the engine/tranny.  If you have a 80's mk1 your earthing cables are over 30 years old, and used up.

On the back of the instrument cluster there are 1 or 2 connectors, you can remove the connectors, remove the plastic shrouds off the connectors on the cluster, carefully pry off the mylar circuit foil from the plastic tongue.





On the Pad side of the tongue place 1 piece of electrical tape and return the mylar over the tongue, replace the shroud, and you have just "plumped" your pins to make better contact.



Your Clusters have a earthing wire it is brown, and usually on pin 2 of the main connector.  You will use a 3m Scotch Wire splice to splice a wire about 4 inches back from the connector, and tie it directly to the Frame with a self tapping sheet metal screw and a solderless ring connector.





If your Earthing Cables are flaky, which they can and usually are, the Auto and Electrons being stupid, will find any path it can to complete the circuit.

I have seen the Starters use Clutch Cables, Speedo Cables, Accelerator Cables, Sensor grounds, and Electronic Control Units (yep Main computers) for a ground path to complete the circuit.  Which when putting 20-40 Amps of current through those usually fries the cluster, or ECU as well as the sensors…. Making for costly repairs.

Conversly, fuses that are blown, I have seen electrons re-route to secondary paths to battery….via other things and fuses….

Oh, and why VW in their wisdom left "live" wires without shielding is beyond my scope, as in the 2 bare connectors on the Hazards switch… I strongly urge you to use heat shrink on those to prevent blown Turn signal fuses.




Riddle me this;
What do Divorces, Good Coffee, and Electronics all have in common?

They all start with good grounds.

Thanks for all the help and pictues! I will hopefully give the above a whirl tomorrow and report back. Thanks again.

As rubjonny said check the earth/brown wire on the back right hand side of the rocker cover, I had the same problem and was the wire had broken away from the ring connector so stripped some more off the wire and fitted a new ring connector and fitted so all working now.