Relay — location and designation (Audi 100 C3)

Depending on the modification and version of the electrical equipment, the number of relays may vary significantly. The relays are located in the mounting block in the power unit compartment and the relay block located on the left under the instrument panel.

Location of the relay in the mounting block

relay No	Name	Catalog Nt
1	Fog light switch relay	431 951 253 A
2	Cooling system fan relay	431 951 253 D
3	Forced idle relay:	443 919 096 C (443 919 096 E) 1)
	- vehicles with 5-cylinder fuel-injected engines
	— cars with 5-cylinder carburetor engines with manual transmission	443 919 096 A
	- cars with 5-cylinder carburetor engines with automatic transmission	443 919 096
	- cars with 4-cylinder carburetor engines with gear indicator and economy meter	811 919 096 A
	Gear indicator and economy meter relay:
	- diesel cars	171 919 092 A
	- cars with turbocharged diesel engines	171 919 092 C
	- vehicles with 4-cylinder diesel or turbocharged diesel	171 919 091
4	Headlight Washer Relay	413 955 535
5	External Lighting Switch Contact "X" Load Relay	171 937 503 A
6	Relay for control and switching on of the air conditioner vacuum valve	431 951 253 0
7	Horn relay	431 951 253 A
8	Automatic transmission relay (on vehicles with manual transmission, a jumper is installed between terminals "36" and "38")	431 951 253 A
9	Windshield wiper relay	431 955 531
10	Fuel pump activation relay Fuel pump activation relay on vehicles with 5-cylinder engines with rev limiter	433 907 385 2)
	Fuel pump activation relay for vehicles with 4- or 5-cylinder engines without a rev limiter	443 906 059 2)
	Intake manifold heating relay	443 951 253 3)
	Heater switch relay	171 911 261 C 4)
11	Air conditioner electromagnetic clutch activation relay	431 951 253 A

1) On the US version
2) On vehicles with fuel-injected engines
3) On cars with carburetor engines
4) On diesel vehicles

relay No	Name	Catalogue No
1	Brake lining wear indicator lamp relay	431 951 253 A
2	Seat heating relay	431 951 253 A
3	Pulse relay	813 906 064
	Additional starting relay for the automatic vehicle start-up system	431 951 253 A
4	Time-delay relay	433 919 577
	Relay for switching on and off the rear window heating of the automatic vehicle activation system	431 951 253 A
5	Oil Pressure Warning Light Relay:
	- cars with 4-cylinder petrol engines	433 919 082
	- cars with 5-cylinder petrol engines	433 919 082
	- cars with 5-cylinder diesel engines	433 919 082 A
	Seat Belt Warning Light Relay	443 919 469
6	Relay for switching on the sound signaling device of unfastened seat belts	857 919 439
	Fog light relay	431 951253 F 1)
	Relay for switching on external lighting when driving during daytime	431 951 253 D 1)
	Anti-theft alarm relay	437 927 827
7	Maximum voltage relay	437 927 825 2)
i	Time delay relay	431 951 253 B
9	Air conditioner safety relay	431 951 253 B
10	Cooling system fan motor switch relay	431 951 253 V 431 951 254 V 3)
11	Cooling system fan motor switch relay
11-12	Electronic control unit for the electric motor of the cooling system fan	443 907 393
13	Backup
14	Rear Window Wiper Relay	171 955 529
15	Injector cooling relay	431 951 253 A
16	Low beam headlight relay	431 951 253 C 1)
	Turn signal relay	431 951 253 A 4)
	Electronic control unit	055 906 086
17	High beam headlight relay	431 951 253 A 1)
	High-power audio signal activation relay	431 951 253 A
	Fuel mixture enrichment relay	431 951 253 C
18	Ignition relay	431 951 253 A 1)
	Relay for switching on special equipment	431 951 253 A 5)
	Oxygen Air Conditioning Sensor Relay	431 951 253 A

1) Option for Sweden
2) On cars with ABS
3) On cars with turbocharged diesel engines
4) By taxi
5) On police cars