when i first had my 4000 the headlight switch burned out and i lost all interior lights on my dashboard and center console. Along with the headlights and tailights.

A mechanic had done a cheap wiring job to fix the driving lights but it was a mess.

Ive recently re wired everything back to original stock wiring and replaced the headlight switch and dimmer switch. both were melted. Now i have all my lights back to normal.

But here is a few remaining issues.

#1: when i turn the light switch to both settings 1 or 2 i have all the lights but no rev counter.

#2: when i turn the lights out, i have a rev counter again, but no dash lights or tail lights/running lights.

#3: when i turn the headlight dimmer down to almost off, the rev counter comes back on, but its not correct. It shows that the engine is resting at 300 rpm when its actually at 950 rpm


so basically, it seems as if the dimmer switch along with the headlight switch has controll of the rev counter somehow.

and my dash lights are seriously dim, could someone send spares? i just need the two little blue bulbs that stick into the rear of the instrument cluster

 

if your switches were literally burned than there is a good chance some other wires got cooked also. sounds like a guage light wire is shorting out the tach signal wire. my friend had a jetta with a burned up wire for the radio that got so hot it melted 5 or 6 wires around it in multiple spots thruout the harness.

my headlight switch is a little wonkey too, getting the guage lights and runners to work that is. maybe I shoud replace it before it gets worse. . .

 

Check the ground wires. for the instrument cluster and there may be one going to the headlight switch. All ground wires are brown on the Audis. A lot of your problems sound like a floating ground. When your lights are off the voltage can back feed through some other circuit and create a ground and your tach will work ok as it doesn't draw much current and the 12 volts going into the tach can return to 0 volts/ground or the ground may be there but have a high resistance. Voltage is dropped across a resistance. If the resistance stays the same the more current you draw the more voltage is dropped across that resistance.(Look up Ohms Law) Any voltage dropped at that resistance is voltage LOST to your tach, lights or other load. When you turn on the lights most of the voltage is lost to the high resistance to ground and your lights are dim and your tach doesn't work. Get the Bently book for your car with the wiring diagrams. Without the book look for your brown wire going to the instrument cluster and trace it back to the connection to the car body. Is it good. Look at the printed circuit traces on the instrument cluster where the ground wire attaches at the plug. Trace from the brown wire on the plug along the traces to the lamp sockets for the dash lamps. It may be easier to trace backwards from the lamps sockets to the plug. Do you have a Digital multimeter? If not you can buy a halfway decent one for 20-30 dollars at radio shack or sears. Or go to haborfreight and buy on of their cheapo $2.99 meters. But you get what you pay for. I bought a couple to play with and they are not very accurate but probably good enough for what you need here. To look for voltage drop in your ground circuit hook the black lead of the meter to a GOOD metal spot on the car body or get some extra wire and run it to the negative post of the battery and hook up there. Meter is set of 20 volt DC range. Turn on the lights. Then take your positve lead and start checking from the ground point on the body (should measure 0 volts) along the brown wire up to the instrument cluster and along the traces till you find a large (a volt to several volts) voltage drop. Look for a wire pulled pulled off, a broken wire a loose connection, corrosion a bad socket connection etc. I hope this helps.