Headlight Motor Circuit – Operation and Repair – 2.5L NA

Overview

This guide outlines the operation and repair of the headlight motor circuit for the Porsche 944 (8-valve engine) for pre-1985.5 (1983–1985.5) and 1985.5 onwards (1986–1988) models. The headlight motor circuit controls the raising and lowering of the headlights, ensuring proper functionality for nighttime driving. Proper maintenance and repair are critical to avoid issues like headlights failing to move or misalignment, which can affect visibility and vehicle aesthetics.

Pink and blue text represent links to additional resources, tools, parts, and partner websites.

Tools Required

• 10mm (3/8 inch) wrench
• Phillips screwdriver
• Flathead screwdriver
• Ohmmeter
• Wire brush or fine sandpaper
• Needle-nose pliers
• Soldering iron and solder
• Spade-type female connector
• 12V battery or battery charger

Parts Required

• Fuse, 16A (Pre-85.5): 944 612 211 00
• Fuse, 7.5A (85.5 Onwards): 944 612 211 01
• Fuse, 25A (85.5 Onwards): 944 612 211 02
• Headlight motor relay (if damaged): 944 615 112 00
• Rotary switch brush (if damaged, custom-made or sourced)
• Automotive GOOP for rubber boot repair
• Lithium-based grease

Step-by-Step Procedure

Step 1: Verify Fuse Values

1. Locate the fuse box. For Pre-85.5 models, check the additional fuse box near the main fuse panel. For 85.5 Onwards models, check the main fuse panel.

For Pre-85.5 models:
Ensure fuse #1 in the additional fuse box is a 16A fuse (944 612 211 00).

For 85.5 Onwards models:
Check fuse #16 (7.5A, 944 612 211 01) for the red/green or yellow/blue wire, fuse #37 (7.5A, 944 612 211 01) for the yellow/blue wire, and fuse #2 (25A, 944 612 211 02) for the red/blue wire.

2. Replace any incorrect or blown fuses with the specified part numbers.

Step 2: Test Headlight Motor Cycle

3. Remove the appropriate fuse to prevent automatic motor operation: Fuse #1 (Pre-85.5) or Fuse #2 (85.5 Onwards).
4. Turn the manual control knob on the headlight motor to cycle the system through one full raise-and-lower motion. Note any points of excessive resistance.
5. Inspect the headlight assembly where it passes through the bodywork for rubbing or foreign material. Remove any debris.
6. Check the sheet metal tabs above the radiator on both sides of the car. Each tab has three small cap screws. Adjust these screws using a Phillips screwdriver to align the linkage if necessary. Tighten to 5 Nm (3.7 ft-lbs).
7. If front-end damage is suspected, consult a professional body shop to address any metal folds interfering with headlight movement.
8. Apply lithium-based grease to the ball joints in the headlight linkage to reduce resistance.

Step 3: Adjust Headlight Position (If Too High or Too Low)

9. Start the car and turn on the headlights.
10. Locate the linkage connected to the motor shaft. Unscrew it using a 10mm (3/8 inch) wrench without rotating the linkage.
11. Manually reposition the headlights to the desired height while holding the disconnected linkage.
12. Reconnect the linkage to the motor shaft and tighten to 10 Nm (7.4 ft-lbs).
13. Turn the headlights on and off to verify the correct position. Repeat the adjustment if necessary.

Step 4: Diagnose Headlights That Turn On But Do Not Move

14. Recheck fuses as described in Step 1.
15. Disconnect the 4-pin connector from the headlight motor.
16. Measure voltages at the connector with an ohmmeter under the following conditions:

– Ignition on, light switch off: Brown and grey (Pre-85.5) or yellow/blue (85.5 Onwards) should read 0 volts; red/green and red/blue should read 12 volts.

– Ignition on, light switch on: Brown and red/green should read 0 volts; grey (Pre-85.5) or yellow/blue (85.5 Onwards) and red/blue should read 12 volts.

– Ignition off, light switch off: Brown and grey (Pre-85.5) or yellow/blue (85.5 Onwards) should read 0 volts; red/green and red/blue should read 12 volts.

17. If voltages are incorrect, test the headlight relay and dash switch with an ohmmeter for continuity. Replace the relay (944 615 112 00) or switch if faulty.
18. If voltages are correct, proceed to bench-test the motor assembly.

Step 5: Bench-Test the Headlight Motor Assembly

19. Remove the motor assembly from the car:

Disconnect the motor shaft from the linkage.
Remove the 4-pin electrical connector.
Remove the three screws securing the motor assembly using a Phillips screwdriver.

20. Remove the rubber covers from the motor assembly and inspect for splits or damage.
21. Check the relay points for burning. File with fine sandpaper or replace the relay (944 615 112 00) if damaged.
22. Test the relay coil continuity with an ohmmeter (should read ~65 ohms). Replace the relay if there is no continuity.
23. Remove the relay block and inspect the 4-pin connector for damaged male or female connectors. Source compatible connectors from a local supplier if necessary.
24. Verify wiring at the relay block: Terminals 1 and 3 connect to the motor and red/blue wire; terminals 2 and 5 connect to the relay coil, ground, and center brush; terminal 5 has no connection.
25. Remove the rotary switch cover and inspect the brushes. If damaged, de-solder and replace with a custom brass piece or appliance repair part.
26. Test the motor:

Remove the relay from the relay block using a flathead screwdriver.
Attach a spade-type female connector to a wire and insert it into terminal 1 or 3 (connected to the green motor wire).
Connect the motor case to the negative terminal of a 12V battery and the wire to the positive terminal.
If the motor does not turn, check connections. Replace the motor if it still fails.

Step 6: Repair Rubber Boots (If Damaged)

27. Clean and lightly sand the areas around any splits in the rubber boots.
28. Apply tape to the inside of the split to hold the boot together.
29. Apply multiple layers of automotive GOOP to the outside of the split, allowing each layer to dry fully.
30. Remove the tape and apply GOOP to the inside of the split.
31. Trim excess GOOP and refit the boot onto the motor assembly.

Post Procedure Checklist

• Verify headlights raise and lower smoothly without binding.
• Check headlight alignment and adjust if necessary.
• Ensure all fuses are correctly rated and seated.
• Test headlight operation with the dash switch in both on and off positions.
• Inspect rubber boots for secure fit and no leaks.
• Confirm no loose screws or linkages in the headlight assembly.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manuals
• YouTube