Updated: 20-Nov-2024

Looking for factory-style electrical connectors? Tap here.


Fuse & Relay Panel

The Bentley Service Manual has numerous errors in its list for relays and fuses. Most of those errors have been corrected here! However, it's wise to verify your relays using the relay part numbers listed below, especially for the 1980-1982 cars. Fuse & Relay Panel.

The fuse/relay panel is located under the dash, driver's side, behind the kneebar.

IMPORTANT NOTES:

Panel Diagrams
1980-1982
K-Jetronic
1983-1985
K-Jetronic
1986-1987
K-Jetronic
7/1987-1993*
K-Jetronic
1990-1993
Digifant

Diagram

Actual Panel

Diagram

Actual Panel

Diagram

Actual Panel

Diagram

Actual Panel

Diagram

Actual Panel


Complete electrical system guide: Electrical System Download

The above guide contains relay & fuse diagrams, relay panel pin-out schematics, and a guide to reading current flow wiring diagrams.

* Up to 1993 outside North America.

Relays

Relay part numbers, both original and replacement (including aftermarket where available), are now in a PDF, which also contains relay pin diagrams.

Relay part number guide: Relay Guide Download

Ground Locations

1980-1986

Main ground cables/straps:
  • Battery to the left frame rail; frame rail to the transmission
  • Valve cover to the ignition coil bracket
  • Fender to hood
  • A/C compressor to battery (or engine block)
  • Ignition Control Unit to battery
Ground locations:
  • Fuse/relay panel
  • Steering column
  • Cold-start valve (K-Jetronic only)
  • Trunk, rear left and right
  • Dash wiring harness
  • Ignition distributor

1987-1989

Main ground cables/straps:
  • Battery to the left frame rail; frame rail to the transmission
  • Valve cover to the ignition coil bracket
  • Fender to hood
  • A/C compressor to battery (or alternator)
  • Ignition Control Unit to battery
Ground locations:
  • Fuse/relay panel
  • Steering column
  • Cold-start valve (K-Jetronic only)
  • Trunk, rear left and right
  • Dash wiring harness
  • Ignition distributor ('87)
  • Engine bay, front left and right ('88+)

1990-1993

Main ground cables/straps:
  • Battery to the left frame rail; frame rail to the transmission
  • Valve cover to the ignition coil bracket
  • Fender to hood
  • Digifant ECU to firewall
  • A/C compressor to engine block (or alternator)
Ground locations:
  • Fuse/relay panel
  • Instrument cluster wiring harness
  • Steering column
  • Trunk, rear left and right
  • Engine bay, front left and right
  • Horns ('91+)

Please use the Bentley Service Manual wiring diagrams for complete wire routing for your particular car.

Keep your electrical system tip-top by cleaning your electrical connections!

K-Jetronic photos of main grounds

Digifant photos of main grounds

Wiring

Wiring Diagrams

Wiring diagrams can be found in the Bentley Service Manual as well as the Haynes Repair Manual. NOTE: Those with 1986 Cabriolets should follow both the 1986 and the 1987 Bentley main wiring diagrams; much, but not all, of the wiring in a 1986 resembles the 1987 diagrams and the latter diagrams are easier to read.

How to read VW current track wiring diagrams: Wiring Guide Download

Help Icons No AttributionWarm wires

Warm-to-the-touch wires are not at all unusual in these cars, due, in part, to the way they were wired at the factory.

However, wires that become so warm or hot that they melt their insulation and/or smoke are cause for concern. An overly warm wire is indicative of a circuit with high resistance. This high resistance can be caused by various issues: bad ground connections, poor wire connections, faulty switch, faulty relay, etc.

Voltage Drop

Voltage drop is a common malady on Cabriolets due to a poorly designed electrical system. Voltage drop can be witnessed on the VDO volt gauge with the engine running: When turning on the headlights, for instance, the volts will drop from 14 down to 12 (the drop is actually more severe when reading the voltage at the battery, then at the headlight; this is because the volt gauge is not 100% accurate); the volt gauge needle will also bounce in rhythm with the turn indicators. If the charging system is in good working order and all ground wires/connections are in good shape, this is nothing to really worry about. However, to combat voltage drop (and to increase headlight output), install headlight relays, clean all ground contacts and replace ground cables.

Voltage readings (using a DVOM at the battery, not the in-car VDO gauge):

OBD Diagnostics

Test ports are accessed under the shift boot, towards the front.

NOTE: Only Cabriolets equipped with Digifant I fuel injection have the OBD I diagnostic ports. Furthermore, an OBD II diagnostic tool cannot be used to pull fault codes from an OBD I system unless it has an adapter!

OBD I diagnostics guide: OBD Guide Download

Power Windows

Help Icons No AttributionPower Windows Don't Work (under construction)

  1. Check fuse #17, and the fuse in relay position 17. Fuses okay? Yes: Proceed to step 2. No: Replace blown fuse(s).

  2. Check for voltage at the power window control unit (located beneath the dash, passenger side; key to battery-on position). Is there voltage? Yes: Proceed to step 3. No: Remove the control unit and check for broken wires, broken internal connections, melted wires/connectors, water. If there is water intrusion: A) dry the control unit thoroughly; B) reseal the air plenum in the rain tray. If the control unit is still unresponsive or has melted wires, you'll need to buy a new/used one (part #191959875); and make sure the fuses are good and of proper amperage.

  3. Check for voltage at each window switch. Is there voltage? Yes: No:

  4. Please refer to this thread and/or this thread and/or this thread on VWvortex for additional info.

Lights

Headlight Types

Headlight guide: Headlight Guide Download

Headlight Relays

Whether you are upgrading your headlights or not, it is a very wise idea to relay the headlights. The stock headlight wiring uses paltry 16 gauge wires, uses the headlight switch as a power source, and contains lengthy wire runs, all of which cause resistance and, ultimately, voltage drop at the headlights thereby reducing each lamp's luminosity. Adding relays powers the headlights directly from the battery/alternator, will reduce voltage drop in the electrical system, will extend the life of the alternator, headlight switch and ignition switch, will increase the light output giving you whiter & brighter light, and will reduce the chances of the headlight switch overheating.

A standard Halogen sealed-beam headlamp produces 100% of its light output at 12.8 volts (or 13.2 volts in Europe) or above. Take a voltage reading at one of your headlights. What does your meter read? My meter read 10.86 volts at each lamp, lo-beam. Using voltage drop figures found on the Web, at 10.86 volts, each of those headlamps was producing less than 53% of their possible light output. After adding relays to the headlight circuit, each headlight's voltage jumped up to 13.36 volts, which means the lamps are now producing 100% of their possible light output. Headlight Relay Example

Further information regarding headlight wiring, voltage drop, adding relays, etc. can be found at Daniel Stern Lighting.

Headlight Switches

Three different headlight switch types were used in 1981+ Cabriolets. If you're replacing the switch, use the information below to ensure you're buying the correct one! For example, AutohausAZ lists the 321-K switch for a 1990 Cabriolet, which is the wrong one! Tap on the icons to see examples.

City Lights

If you are installing city lights on a North American Cabriolet, wire the lights to the stock wiring based on how you want the lights to be used.

Stock wiring in the car:

If you're installing Euro bumper lights that include city lights, you'll need to splice the two ground wires together prior to wiring them to the car's brown ground wires.

Disabling Day-time Running Lights Canada flag

Canadian Cabriolets built from 1990-1993 have day-time running lights (DRLs) from the factory, as Canadian law requires DRLs. If, for whatever reason, you want/need to disable the factory DRL system:

  1. Pull the headlight switch and place electrical tape over the TFL pin
  2. Reinstall switch

If your switch does not have a wire going to the TFL pin, or is without a TFL pin, your car may have hard-wired day-time running lights (DRLs) from the factory. To disable DRLs on these cars (thanks to Rob for the info):

  1. Locate the yellow 20-gauge wire on the back of the headlight switch
  2. Either push/pull it out of the harness connector, or cut it and cap/tape it off
  3. You can also disconnect the same yellow 20-gauge wire from the A-21 pin on the back of the relay panel

Installing LEDs

Want to brighten up your lights, or change their color, or reduce the power drain? Replace the original incandescent bulbs with LEDs. LEDs have come a long way in the last several years. Rather than buying LEDs and the appropriate resistors, you can now buy LEDs that include resistors for a plug-and-play application in most instances. Download the DIY Guide for a how-to. Tap here for a breakdown of what you need.

Help Icons No AttributionReverse Lights Do Not Work

If the fuse/relay and bulbs are okay, replace the reverse (back-up) light switch located on top of the transmission (on automatics, the switch is connected to/near the shift lever).

To test the reverse light switch: Disconnect the electrical plug, jump the black and black/blue wire terminals, turn the ignition switch to the battery-on position. If the lights turn on, the switch is faulty.

Sensors, Senders, Switches

Windshield Wipers

Adding variable wiper option

Look for relay #357955531 or #3B0955531 (has a printed 99. on it in OEM form) found in the following vehicles:

Or, order a new one from an auto parts store. It is a plug and play swap; replace your existing relay with the new one.

To program the variable feature: "Pull the lever into the intermittent position, and, as the wiper does it's sweep, Tap back into the stop position, if you want a 3 second gap, then wait 3 seconds, and Tap back into the intermittent position. Bam, you just programmed a 3 second timing."

If ^that doesn't work: "Pull the stalk towards you to (for windshield washers) while the wipers are set to intermittent. This initiates the timer. If left alone at this point it will default to the 20s interval. Pull the stalk towards you again and it will set the timer to that interval, anywhere from 5 to 20 seconds."

Horns

Where are the horns?

The dual-tone horns are mounted to a bracket, which is mounted to the front left frame rail. Image Icon

Rev Limiters

K-Jetronic:

Rev limiter is built into the fuel pump relay. When the RPM reaches the built-in limit, the fuel pump relay shuts off the fuel pumps. This is a safety feature; however, the relay can be replaced with a "no-rev" or "hi-rev" version so that the cut-off point is eliminated or increased to approximately 7500 rpm.


Digifant:

Rev limiter is built into the ECU and cannot be altered.