Mercedes-Benz 350SD 1990 - 1990-93 MERCEDES-BENZ 300D, 350SD & 350SDL

Mercedes-Benz 350SD 1990 - RELAYS & TIMERS

Mercedes-Benz 350SD 1990 RELAYS & TIMERS LOCATION

Component Name, Number	Location
A/C Auxiliary Fan Relays, K9	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
A/C Auxiliary Fan Pre-Resistor Relay, B	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Anti-Theft Alarm Relay, E	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Auxiliary Heater Circulating Pump Relay, K15	Under passenger-side foot panel. See Fig. 2 .
Combination Relay (Turn Signal, Rear Defogger, Windshield Wiper), H	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Convenience Relay, F	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Cruise Control/Engine Overload Protection Relay	Behind battery.
Dome Light Delay Relay	In front dome light assembly.
Head Restraint Adjustment Relay	Underneath applicable seat.
Headlight Washer Relay, D	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Heated Rear Window Relay, Outside (Special Protection), K13	Left rear of luggage compartment, behind trim panel. See Fig. 3 .
Heated Rear Window Relay, K13/1	Left rear of luggage compartment, behind trim panel. See Fig. 3 .
Heated Rear Window Relay (Special Protection), N11/1	Left rear of luggage compartment, behind trim panel. See Fig. 3 .
Heated Seat Relays	Under carpet in front of both front seats.
Overvoltage Protection Relay, K1	Right rear corner of engine compartment, attached to engine heat shield. See Fig. 4 .
Power Window Relay, K6	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Power Seat Relay, A	Left rear corner of engine compartment, in fuse/relay block.
Pressurizing Pump Relay, K20	Behind brake master cylinder, attached to engine heat shield. See Fig. 4 .
Rear Window Intermittent Wiper Timer (Wagon)	Inside left rear corner of tailgate.
Restart Delay Relay	Left rear corner of engine compartment, in fuse/relay block.
Seat Belt Warning Relay (Coupe), G	Left rear corner of engine compartment, in fuse/relay block. See Fig. 1 .
Transmission Upshift Delay Relay	Right rear corner of engine compartment, attached to engine heat shield.

Mercedes-Benz 350SD 1990 - CIRCUIT PROTECTION DEVICES

Mercedes-Benz 350SD 1990 CIRCUIT PROTECTION DEVICES LOCATION

Component Name, Number	Location
Fuse & Relay Box, F1	Left rear corner of engine compartment.

Mercedes-Benz 350SD 1990 - CONTROL UNITS

Mercedes-Benz 350SD 1990 CONTROL UNITS LOCATION

Component Name, Number	Location
ABS Control Unit, N30	Center rear of engine compartment, mounted to firewall. See Fig. 4 .
ABS/ASR Control Unit, N30/1	Center rear of engine compartment, mounted to firewall. See Fig. 4 .
A/C Compressor Control Unit	Right rear of engine compartment, behind battery.
A/C Temperature Control Unit	Under right side of dash, behind glove box.
Amplifier Speaker Control Unit, N40/1	In luggage compartment, behind front trim panel. See Fig. 3 .
Anti-Theft Alarm Control Unit	Under right side of passenger foot rest, near kick panel.
ASD Control Unit, N47	Left rear corner of engine compartment, attached to engine heat shield. See Fig. 4 .
Automatic Climate Control Unit, N22	In center console. See Fig. 5 .
Auxiliary Heater Control Unit, N33	Centered, under passenger-side foot rest. See Fig. 2 .
Control Unit Comfort Seat Adjustment (Left), N31	Under left front seat. See Fig. 6 .
Control Unit Comfort Seat Adjustment (Left With Memory), N31/1	Under left front seat. See Fig. 6 .
Control Unit Comfort Seat Adjustment (Right), N32	Under right front seat. See Fig. 6 .
Control Unit Comfort Seat Adjustment (Right With Memory), N32/2	Under right front seat. See Fig. 6 .
Control Unit Compressor Cut-Out, N6	Left rear corner of engine compartment, attached to engine heat shield. See Fig. 4 .
Control Unit Electronic Accelerator, N4/1	Under dash left of steering column. See Fig. 5 .
Convenience Control Unit	Under left side of rear seat.
Cruise Control Amplifier With Reference Resistor, N4/2	Under dash, left of steering column. See Fig. 5 .
Cruise Control Unit, N4	Under dash, left of steering column. See Fig. 5 .
Daytime Running Light (DRL) Control Unit	Centered, under right side foot rest.
EDS Control Unit, N39	Right rear of engine compartment, behind battery. See Fig. 7 .
EDW Control Unit, N26	Centered, under passenger-side foot rest. See Fig. 2 .
Electronic Blower Regulator Control Unit	Center of cowl, next to heater core.
Exterior Light Failure Monitoring Unit	Left rear corner of engine compartment, in fuse/relay box.
Engine Systems Control Unit (MAS)	Right rear of engine compartment, behind battery.
Emergency Tensioning Retractor (ETR) Control Unit, N2/1	Top of transmission tunnel, behind front console. See Fig. 2 .
Front Seat Heater Control Unit, N25/5	Under respective seats. See Fig. 6 .
Hydropneumatic Suspension Control Unit, N46	Under dash left of steering column. See Fig. 5 .
Idle Speed Control Unit, N8	Centered, under passenger-side foot rest. See Fig. 2 .
Illumination Control Unit	On steering column, behind instrument cluster.
Left Front Power Seat & Steering Column Adjustment Control Unit, N32/3	Under left front seat. See Fig. 6 .
Left Seat Belt Extender Control Unit, N42	In luggage compartment, Behind front trim panel. See Fig. 6 .
Rear Seat Heater Control Unit, N25/6	In luggage compartment, under front trim panel. See Fig. 3 .
Right Seat Belt Extender Control Unit, N43	In luggage compartment, behind front trim panel. See Fig. 6 .
SRS Control Unit, N2/2	Top of transmission tunnel, behind front console. See Fig. 2 .
Tempmatic Control Unit, N20	Under passenger-side of dash, behind glove box. See Fig. 2 .
Trailer Monitoring Control Unit, N28/1	In luggage compartment, under trim panel. See Fig. 3 .
Trip Computer Control Unit, N41	Behind instrument cluster. See Fig. 5 .
Warning Module (Seat Belts), N2/4	Behind instrument cluster, on steering column. See Fig. 5 .

Mercedes-Benz 350SD 1990 - SENDING UNITS & SENSORS

Mercedes-Benz 350SD 1990 SENDING UNITS & SENSORS LOCATION

Component	Location
ABS Wheel Speed Sensors
Front	At steering knuckle.
Rear	Right front of rear differential.
A/C Compressor RPM Sensor	On back of A/C compressor.
A/C In-Car Temperature Sensor	In dome light assembly integrated with aspirator blower.
Air Flow Sensor Potentiometer	Right front of engine compartment, in air intake assembly. See Fig. 7 .
Ambient Temperature Sensor 1	On blower motor housing, left of wiper motor.
Ambient Temperature Sensor 2	Left front corner of front bumper.
Brake Wear Sensors	In front brake pads.
Camshaft Position Sensor	On left side of camshaft front cover.
Control Rod Travel Sensor	On left side of cylinder head. See Fig. 7 .
Coolant Temperature Sensor	On left side of cylinder head. See Fig. 7 .
EDS Pressure Sensor	Right rear of engine compartment. See Fig. 7 .
Engine Speed Sensor (Starter Ring Gear)	Rear of engine, on bell housing.
Evaporator Temperature Sensor	On left side of evaporator housing, above accelerator pedal.
Fuel Level Sensor	On top of fuel tank.
Heater Core Temperature Sensor	Behind center of dashboard, below radio.
Intake Air Temperature Sensor	On air filter housing inlet duct.
Oil Pressure Sensor	At bottom rear of oil filter housing, above starter bolts.
TDC Sensor	Front of engine, above vibration damper.
Vehicle Speed Sensor (Hall Effect)	On back of speedometer.

Mercedes-Benz 350SD 1990 - MOTORS

Mercedes-Benz 350SD 1990 MOTORS LOCATION

Component	Location
A/C Heater Blower Motor	Center front of cowl, behind panel. Near wiper motor.
Adjustable Steering Column Motor	Left of steering column, under lower dash panel.
Auxiliary Coolant Pump (Heater)	Left rear of engine, near steering box.
Auxiliary Fan(s)	Front of radiator.
Headlight Washer Pump	In windshield washer reservoir.
Headlight Wiper Motors	Underneath and rear of each headlight assembly.
Rear Window Sun Shade Motor	In luggage compartment, under rear shelf.
Rear Window Washer Motor	Right rear corner of luggage compartment, behind fuel tank filler tube.
Sliding/Pop-Up Sun Roof Motor
Sedan	On top of left rear wheelwell.
Wagon	Inside left rear quarter panel.
Supply Vacuum Pump Motor (Central Lock System)	Inside box, under right rear seat.
Vacuum Pump Motor	Under right side of rear seat.
Windshield Washer Pump	Right front of engine compartment, in reservoir.
Windshield Wiper Motor
Front	Center front of cowl, behind panel. Left of battery.
Rear (Wagon)	Inside center of tailgate.

Mercedes-Benz 350SD 1990 - SOLENOIDS & SOLENOID VALVES

Mercedes-Benz 350SD 1990 SOLENOIDS & SOLENOID VALVES LOCATION

Component	Location
ARF Vacuum Transducer	Right front corner of engine compartment. See Fig. 7 .
ARF Valve	On turbocharger. See Fig. 7 .
ELR Actuator	Left side of engine. See Fig. 7 .
Kickdown Solenoid (A/T)	At bottom, right rear of transmission.
Upshift Delay Solenoid Valve	On left side of transmission.
Vacuum Transducer Pressure Control Flap	Right front corner of engine compartment. See Fig. 7 .
Vacuum Transducer Charge Pressure Control	Right front corner of engine compartment. See Fig. 7 .

Mercedes-Benz 350SD 1990 - SWITCHES

Mercedes-Benz 350SD 1990 SWITCHES LOCATION

Component	Location
A/C High Pressure Switch	On receiver-drier, behind left headlights.
A/C Receiver-Drier Pressure Switches	On receiver-drier, behind left headlights.
A/T Overload Protection Switch	Left front of transmission.
Back-Up Light Switch	Left side of transmission.
Brake Fluid Level Switch	In brake fluid reservoir.
Brake/Stoplight Switch	On top of brake pedal bracket.
Clutch Pedal Switch (Cruise Control)	On top of pedals bracket.
Coolant Level Switch	In coolant reservoir, on right front fender panel.
Cruise Control Warning Switch	In engine compartment, next to fuse/relay block.
Deceleration Shut-Off Microswitch	Top of intake manifold, on throttle body linkage bracket.
Evaporator Temperature Regulator Switch	In evaporator housing, above passenger footwell.
Intake Manifold Pressure Switch	Top of intake manifold.
Kickdown Switch (A/T)	Under accelerator pedal.
Oil Level Switch	In left side of oil pan.
Parking Brake Switch	On parking brake support at left kick panel.
Power Seat Relay Switch(es)	In front door jambs, below door light switches.
Rear Head Restraint Control Switch	In luggage compartment, under package shelf.
Starter Lock-Out/Back-Up Light Switch	Left side of transmission.
Switching Valve	Underside of thermostat housing.
Throttle Valve Switch	On intake manifold, at base of throttle body.
Windshield Washer System Heater Thermoswitch	Left rear corner of engine hood.

Mercedes-Benz 350SD 1990 - MISCELLANEOUS

Mercedes-Benz 350SD 1990 MISCELLANEOUS LOCATION

Component	Location
A/C Voltage Regulator	Inside blower housing.
Auxiliary Fan Pre-Resistor	Behind left headlights, at lower front of inner fender panel.
Cruise Control Actuator	Under left dash, to right of parking brake support.
Diagnostic Connectors	Lower left front fender panel, forward of strut tower.
California On-Board Diagnostics (16-Pole w/LED)	Right side inner component wall, left of battery.
California On-Board Diagnostics (SRS - 10-Pole)	Below passenger foot rest, right of anti-theft alarm control unit.
Power Seat Diode	In fuse/relay block.
SRS Energy Accumulator	Behind right kick panel, below SRS voltage converter.
SRS Voltage Converter	Behind right kick panel, above SRS energy accumulator.
Speedometer Transmitter	On left rear side of transmission.