Electrical System

Relay Panel

Fuse Panel

The Bentley Service Manual has numerous errors in its list for relays and fuses. Most of those errors have been corrected here! However, please see the last "NOTE".

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

NOTES:

Fuse amperage: Green = 30; Yellow = 20; Blue = 15; Red = 10.
1980-1982 Cabriolets use ceramic fuses.
The 3 fuses below the main fuse row are spares.
If your car has factory-installed heated seats, the relays for this option are under each front seat (P/N 443919533A).
If your car has a factory-installed 2-stage cooling fan ('88-'89), the relay for this fan is mounted to the left front fender (P/N 701919505).
If your car has a factory-installed power top, there is a covered thermo-fuse above the relay panel (P/N 443937105).
If your car has factory- or dealer-installed daytime running lights, there may be a relay in or above the top row of the main panel relays (P/N 701919505).
Because there may be slight discrepancies in relay locations between the years & countries, relay part numbers are provided. Those part numbers listed in gray with a "=>" after them have been superseded (they are provided as references); current part number(s) for those relays follow them in black.

1983-1989

Cold-start enrichment

relay

(1988-1989)

P/N 141951253B

Fuel injection power supply/

"Lambda relay"

P/N 171906381 =>

7M0951253

Pulse relay for cold-start valve

P/N 813906064

A/C thermo-fuse (30)

Idle boost control unit relay

P/N 811905343

Fuel pump relay

P/N 321906059E =>

321906059F,

321906059G

Seat belt warning/ door buzzer relay

P/N 3A0951307

Up-shift indicator control unit relay

(up to 1987)

P/N 371279241 =>

171919091C

A/C relay

P/N 171959141A

Horn relay

P/N 141951253B

Fog lamp relay

(Europe only)

P/N 141951253B

Load reduction relay

P/N 171??????A =>

7M0951253A

Intermittent wiper relay

P/N 321955531A =>

191955531

Turn signals & emergency flasher relay

P/N 111953227D,

1H0953227

1 = Radiator cooling fan
2 = Brake lights; cruise control
3 = Cigarette lighter, radio, clock, interior lights, instrument cluster
4 = Emergency flashers
5 = Fuel pump
6 = Open
7 = Taillights, parking lights, side marker lights - left
8 = Taillights, parking lights, side marker lights - right
9 = Headlights (high beam, right), high beam indicator
10= Headlights (high beam, left)
11= Windshield washer/wipers
12= Heated seat (if installed)

13= Rear window defroster

14= Fresh air (heater) blower
15= Back-up lights; shift console light (A/T); cruise control (manual trans.)
16= Horns
17= Open
18= Seat belt warning light; horn relay; coolant level/ temperature warning light; oil pressure gauge, oil temp gauge, voltmeter; cruise control (auto trans.)
19= Turn signals; brake warning light
20= License plate lights; luggage compartment light
21= Headlights (low beam, left)
22= Headlights (low beam, right)

1990-1993

Power top thermo-fuse (30)

Power window relay

(Europe only?)

P/N 141951253B

Time control unit relay for radiator cooling fan after-run system

P/N 191955532A

Starter inhibitor switch relay

(A/T cars only)

P/N 191927181

(From VIN M-35001, relay is mounted to kneebar)

Coolant low-level warning control unit

P/N 191919376A

A/C thermo-fuse (30)

Power window regulator fuse (20)

Digifant control unit relay

P/N 141951253B

Fuel pump relay

P/N 191906383C

Seat belt warning/ door buzzer relay

P/N 3A0951307

A/C relay

P/N 171959141A

Horn relay

P/N 141951253B

Fog lamp relay

(Europe only)

P/N 141951253B

Load reduction relay

P/N 171??????A =>

7M0951253A

Intermittent wiper relay

P/N 321955531A =>

191955531

Turn signals & emergency flasher relay

P/N 111953227D,

1H0953227

1 = Radiator cooling fan
2 = Brake lights; cruise control (1991-1993)
3 = Cigarette lighter, radio, clock, interior lights, instrument cluster, airbag lights
4 = Emergency flashers
5 = Electric fuel pump, oxygen sensor heater
6 = Open
7 = Taillights, parking lights, side marker lights - left
8 = Taillights, parking lights, side marker lights - right
9 = Headlights (high beam, right), high beam indicator
10= Headlights (high beam, left)
11= Windshield washer/wipers
12= Open

13= Rear window defroster

14= Fresh air (heater) blower
15= Back-up lights; shift console light (A/T); cruise control (1990 manual trans. only)
16= Horns
17= Power windows (switch current)
18= Seat belt warning light, horn relay, coolant level/ temperature warning light, oil pressure gauge, oil temp gauge, voltmeter; heated seats (if installed); cruise control (1990 auto trans. only)
19= Turn signals, brake warning light
20= License plate lights; luggage compartment light; instrument panel lights (1991-1993)
21= Headlights (low beam, left)
22= Headlights (low beam, right)

1980-1982

Fuel Pump*

Intermittent wipers?

Fuel injection power supply

"Lambda relay"

Upshift indicator control unit?

(1982)

Seat belt warning?

Load Reduction?

Fuel Pump*

A/C?

Turn signals, emergency flashers?

blank

1 = Headlights (low beam, left) (8)

2 = Headlights (low beam, right) (8)

3 = Headlights (high beam, left), high beam indicator light (8)

4 = Headlights (high beam, left) (8)

5 = Rear window defogger (16)

6 = Stop lights, emergency flashers (8)

7 = Cigarette lighter, radio, clock, interior lights, instrument cluster (8)

8 = Turn signals, indicator light (8)

Fuel pump fuse (in-line above relay panel or on fuel pump relay) (16)

9 = Back-up lights, horn (8)

10 = Fresh air fan (16)

11 = Windshield washers/wipers (8)

12 = License plate light (8)

13 = Exterior running lights, right (8)

14 = Exterior running lights, left (8)

15 = Radiator fan (25)

Radio fuse (on radio) (5)

*Original fuel pump relay position is 7. However, due to recall compliance, the fuel pump relay may be located in position 1 using a wiring harness to bridge relay positions 7 and 1.

Automatics with intermittent starting issues

Cabriolets with automatic transmissions tend to have hot-start issues due to the idiotic location of the starter. Installing a hot-start relay usually fixes this problem (if not, move on to the starter and/or ignition switch). There are two ways of adding a hot-start relay: the official Volkswagen way, or the aftermarket way; either method will work. If, after installing the hot-start relay, a new starter and a new ignition switch your 1990-1993 automatic Cabriolet continues to have intermittent starting issues, it is most likely due to the starter interlock relay going bad. The starter interlock relay is supposed to be located in position #15 on the relay panel; if it is not, look up, behind the kneebar for a relay stamped 92 and with part #191 927 181. Barring this relay replacement, you can also bypass the interlock system with this fix (reminder: the starter interlock is a safety device required by USA federal mandate from 1990 onward; if you have small children and/or intend to sell the car someday, do not bypass the interlock as the car can now be started in any gear).

Where to get wiring diagrams

Wiring diagrams can be found in the Bentley 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.

Click here for an explanation on how to read the wiring diagrams (56K warning!).

CE1 panel schematics

Connecting the OBD I diagnostic/scan tool

Under the shift boot, towards the front.

NOTE: Only Cabriolets equipped with Digifant I engines have the OBD I diagnostic port; furthermore, an OBD II diagnostic tool cannot be used to pull fault codes from an OBD I system! To repeat: Only Cabriolets with Digifant I have OBD I (they do not have OBD II)!!

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 slightly increase headlight output), install headlight relays, clean all ground contacts and replace ground cables. Click here for further information.

My power windows don't work!

Please refer to this thread and/or this thread and/or this thread on VWvortex.

Reverse lights do not work

If the fuse/relay is okay, replace the reverse (backup) light switch located on top of the transmission (on automatics, the switch is connected to/near the shift lever).

Engine sensors, senders and switches

Oil sensors/senders/switches	Function	Location
Oil temp gauge sender -- nail-head connector	Sends oil temp to gauge	Top of oil filter flange
Oil pressure switch (0.3 bar) & gauge sender	Warns when oil pressure falls to near zero and sends pressure reading to bar gauge	Left side of cylinder head*
Oil pressure switch (1.8 bar) -- 1 pin, white	Warns when oil pressure falls too low at higher (2000+) rpm	Top of oil filter flange*
Coolant sensors/senders/switches	Function	Location
Cooling fan thermo switch -- cars with A/C Cooling fan thermo switch -- cars without A/C	Switches the cooling fan on/off	Lower, left corner of radiator
Cooling fan after-run thermo switch	Controls operation of 2-stage cooling fan after-run system (1988+)	Behind cylinder head cover between #2 and #3 cylinders (1988+)
Coolant temp sensor (OXS/Lambda probe thermo switch, or cold running enrichment switch) -- round, two-pin connector	Controls operation of OXS system (CIS)	Underside of upper radiator hose flange on cylinder head (CIS)
Thermostat	Controls coolant flow	Water pump housing inside the lower radiator hose flange
Coolant temp sensor (thermo-time switch) -- brown two-pin connector	Controls operation of cold-start valve when engine is cold (CIS)	Top of upper radiator hose flange on cylinder head (CIS)
Coolant temp sensor -- blue connector	Provides an engine temp input to the Digifant control unit that is used to boost fuel delivery to improve cold-running driveability (Digifant)	Coolant flange on cylinder head (Digifant)
Coolant temp gauge sender -- single, nail-head connector Coolant temp gauge sender -- white two-pin connector	Sends coolant temperature to dash gauge and warning system (CIS)	Top of upper radiator hose flange on cylinder head (CIS)
Coolant temp gauge sender -- black connector	Sends coolant temperature to dash gauge and warning system (Digifant)	Coolant flange on cylinder head (Digifant)
Coolant level sensor	Senses level in coolant expansion tank; when the level is too low, the sensor sends a signal to the idiot light in the dash cluster (Digifant)	On coolant expansion tank (Digifant)
Misc. sensors/senders/switches	Function	Location
Back-up light switch & up-shift indicator -- manual trans	Turns back-up lights on when transmission is put into reverse; disables up-shift system when in 5th or reverse gears	On top of transmission bell housing
Back-up light switch -- auto trans	Turns back-up lights on when transmission is put into reverse	Base of shift lever in passenger compartment
Up-shift indicator vacuum switch -- manual trans	Relays engine load to the up-shift control unit	Connected to vacuum line to/from distributor
Cruise control switch -- brake	Turns off cruise control system when brake pedal is pressed	Above brake pedal
Cold-running enrichment vacuum switch -- 1987-1989	Interrupts cold-running enrichment above idle (CIS)	At front of intake manifold off of the vacuum line going to brake master cylinder (CIS)
Idle switch	CIS: Signals control unit when throttle is fully closed for idle air stabilizer control and deceleration fuel shut-off Digifant: Signals Digifant control unit when throttle valve is fully closed at idle	On throttle body connected to the full-throttle switch
Full-throttle switch	Signals control unit with a signal when the throttle valve is fully open for full-throttle enrichment	On throttle body (Digifant) (CIS)
Mechanical air flow sensor -- CIS only	Measures intake air flow which then operates the control plunger in the fuel distributor for the proper metering of fuel	Under rubber boot on air filter housing, next to the fuel distributor
Electronic air flow sensor -- Digifant only	Measures intake air flow; signals from this sensor and the ignition distributor are sent to the ECU for the proper metering of fuel	Side of intake air filter housing
Knock sensor -- Digifant only	Senses engine knock	Front of engine block
Oxygen sensor (Digifant) (Calif. Digifant) (CIS)	Sends signal of combustion efficiency to the ECU for fine-tuning of the air-to-fuel mixture (each fuel injection system processes the signals differently; consult Bentley Manual for further info)	Back side of engine, mounted in exhaust manifold
*Bentley Service Manual has this gauge's location listed incorrectly

Rev limiters

The CIS Cabriolets have a rev limiter built into the fuel pump relay. When the rpm's reach 6500 or so, the fuel pump relay shuts off the fuel pumps. This is a safety feature; however, the relay can be replaced with part #321 906 059 F so that the cut-off point is increased to 7500-8000 rpm's. It is highly unwise to bypass this feature by installing a horn relay in place of the fuel pump relay or rewiring the fuel pump relay because when the key is turned to the "battery-on" position, the pumps will run continuously, even in the event of an accident which could be cause for a very dangerous, if not fatal, situation. Digifant Cabriolets have a rev limiter built into the ECU and cannot be altered.

Electrical terminal contact numbers

Ignition		Electric Motors
Contact	Meaning	Contact	Meaning
1	coil, distributor (low voltage)	32	return
1a, 1b	distributor with two separate circuits (low voltage)	33	main terminal (swap of 32 and 33 is possible)
2	breaker points	33a	limit
4	coil, distributor (high voltage)	33b	field
4a, 4b	distributor with two separate circuits (high voltage)	33f	2. slow rpm
7	terminal on ballast resistor to distributor	33g	3. slow rpm
15	battery+ from ignition switch	33h	4. slow rpm
15a	from starter motor to coil	33L	rotation left
Battery		33R	rotation right
Contact	Meaning	Wipers/Washers
15	battery+ through ignition switch	Contact	Meaning
30	from battery+ direct (to component)	53	wiper motor + in
31	return to battery- or direct to ground	53a	limit stop+
31a	return to battery- 12/24 V relay	53b	limit stop field
31b	return to battery- or ground through switch	53c	washer pump
31c	return to battery- 12/24 V relay	53e	stop field
31c	return to battery- 12/24 V relay	53i	wiper motor with permanent magnet, third brush for high speed
Relay Contacts		AC Generator
Contact	Meaning	Contact	Meaning
87	common contact	51	DC at rectifiers
87a	normally closed contact	51e	as 51, with choke coil
87b	normally open contact	59	AC out, rectifier in, light switch
88	common contact 2	59a	charge, rotor out
88a	normally closed contact 2	64	generator control light
88b	normally open contact 2
Turn Indicators		Alternator & Voltage Regulator
Contact	Meaning	Contact	Meaning
49	flasher unit in	61	charge control light
49a	flasher unit out, indicator switch in	B+	Battery +
49b	out 2. flasher circuit	B-	Battery -
49c	out 3. flasher circuit	D+	Dynamo +
C	1st flasher indicator light	D-	Dynamo -
C2	2nd flasher indicator light	DF	Dynamo field
C3	3rd flasher indicator light	DF1	Dynamo field 1
L	indicator lights left	DF2	Dynamo field 2
R	indicator lights right	U, V, W	AC three phase terminals
L54	lights out, left