Fuses, relays and control units (Audi 100 C3)

Relay and fuse box

Fuse number	Nominal current, A	Circuits protected by fuses
1	15	Fog lights
2	15	Direction indicators (in emergency mode)
3	25	Horn. Cigarette lighter. Map light. Interior light. Passenger mirror light. Lower interior light
4	15	Brake light. Luggage compartment light bulb
5	—	Spare
6	5	Right headlight (side light). Right rear light (side light)
7	5	Left headlight (side light). Left rear light (side light)
8	10	Right headlight (high beam). High beam indicator lamp
9	10	Left headlight (high beam)
10	10	Right headlight (low beam)
11	10	Left headlight (low beam)
12	15	Instrument cluster lighting lamps. Reversing light lamps. On-board control system unit
13	15	Fuel electric pump
14	15	Instrument lighting lamps. License plate lighting lamps. Glove compartment lighting lamp. Underhood lamp
15	15	Windscreen wiper motor. Direction indicators (in turn indication mode)
16	30	Rear window heating element
17	30	Heater Fan Motor. Air Conditioner Fan Motor
18	25	Electric motor for sunroof drive
19	10	Centralized door locking system. Electric motor for the drive of the outside rear-view mirrors
20	30	Front seat heating elements
21	25	Rear cigarette lighter
22	80	Diesel Engine Heater
A	10	Spare
IN*	15	Memory device for electric drive for adjusting the position of front seats
E*	30	Electric window lift motors
F	30	Towing device
I	—	Spare fuses

* Automatic switches that open the circuit when overloaded and close it after a short period of time.

Additional relay block under the instrument panel

Location of relays and control units on the vehicle: a – location of relays and control units on the instrument panel; b – location of control units in the car interior; in – location of the control unit in the luggage compartment.

1 - ignition switch (possible position);
2 - additional relay block;
3 - cruise control system control unit;
4 - direction indicator relay;
5 - diagnostic block;
6 - air conditioning control unit;
7 - altitude sensor;
8 - KE-Jetronic fuel injection system control unit;
9 - control unit for front seats with electrical adjustment;
10 - Anti-lock braking system control unit;
11 - battery (for cars with air conditioning);
12 - Engine fuel pump relay;
13 - control unit for lamps in rear lights

The fuse and relay box is located at the rear of the engine compartment on the right or left side of the water drain cover (depending on the model). To replace the fuses, remove the cover of the unit by unfastening the clips. The location of the fuses, the circuits they protect, and the nominal current of the fuse are indicated on the inside of the cover of the unit.

The plastic fuse housings are available in different colours, corresponding to the rated current.

Part of the relay is located in the fuse box, and the other is in a separate additional relay block in the passenger compartment on the left side under the instrument panel. To check the relay for proper operation, turn the corresponding system on and off several times. If you do not hear the characteristic clicks, then the relay is faulty and must be replaced. The relay to be replaced is simply pulled out of its socket.

Location of the relay in the mounting block
N relay	Name	Catalog number
I	Fog light relay	431 951 253 A
II	Cooling system fan relay	431 951 253 D
III	Forced idle relay on a car:	443 919 096 C (443 919 096 E)*
	– with 5-cylinder engines with fuel injection	443 919 096 C (443 919 096 E)*
	- with 5-cylinder carburetor engines with mechanical KP	443 919 096 A
	- with 5-cylinder carburetor engines with automatic KP	443 919 096
	– with 4-cylinder carburetor engines with gear indicator and economy meter	811 919 096 A
	Relay for gear indicator and economy meter on a car:
	- diesel	171 919 092 A
	• with turbocharged diesel	171 919 092 C
	• with 4-cylinder diesel or turbocharged diesel	171 919 091*
IV	Headlight Washer Relay	413 955 535
V	Relay for unloading contact "X" of the outdoor lighting switch	171 937 503 A
VI	Relay for control and switching on of the air conditioner vacuum valve	431 951 253 D
VII	Horn relay	431 951 253 A
VIII	Automatic transmission relay (on vehicles with manual transmission, a jumper is installed between terminals "36" and "38")	431 951 253 A
IX	Windshield wiper relay	431 955 531
X	Fuel pump activation relay:
	- relay for switching on the fuel electric pump on vehicles with 5-cylinder engines with a speed limiter	443 907 385**
	– fuel pump activation relay on vehicles with 4- or 5-cylinder engines without a speed limiter	443 906 059**
	Intake manifold heating relay**	443 951 253
	Heater switch relay***	171 911 261 C
XI	Air conditioner electromagnetic clutch activation relay****	431 951 253 A
* On the US version
** On vehicles with fuel injection engines
*** On cars with carburetor engines
**** On diesel vehicles

Relay block
N relay	Name	Catalog number
I	Brake Pad Wear Indicator Lamp Relay	431 951 253 A
II	Seat heating relay	431 951 253 A
III	Pulse relay	813 906 064
III	Additional starting relay for the automatic vehicle start-up system	431 951 253 A
IV	Time-delay relay	433 919 577
IV	Relay for switching on and off the rear window heating of the automatic vehicle activation system	431 951 253 A
V	Oil pressure warning light relay on a car:
	– with 4-cylinder petrol engines	433 919 082
	– with 5-cylinder petrol engines	433 919 082
	– with 5-cylinder diesel engines	433 919 082 A
	Seat Belt Warning Light Relay	443 919 469
VI	Relay for switching on the sound signaling device of unfastened seat belts	857 919 439
	Fog light relay	431 951 253 F*
	Relay for switching on external lighting when driving during daytime	431 951 253 D*
	Anti-theft alarm relay	437 927 827
VII	Maximum voltage relay	437 927 825**
VIII	Time delay relay	431 951 253 B
IX	Air conditioner safety relay	431 951 253 B
X	Cooling system fan motor switch relay	431 951 253 B
XI	Cooling system fan motor switch relay	431 951 254 B***
XI – XII	Electronic control unit for the electric motor of the cooling system fan	443 907 393
XIII	Backup
XIV	Rear Window Wiper Relay	171 955 529
XV	Injector cooling relay	431 951 253 A
XVI	Low beam headlight relay	431 951 253 C*
	Turn signal relay	431 951 253 A****
	Electronic control unit	055 906 086
XVII	High beam headlight relay	431 951 253 A*
	High-power audio signal activation relay	431 951 253 A
	Fuel mixture enrichment relay	431 951 253 C
XVIII	Ignition relay	431 951 253 A*
XVIII	Oxygen Air Conditioning Sensor Relay	431 951 253 A
* Option for Sweden
** On vehicles with ABS
*** On cars with turbocharged diesel
**** By taxi