Headlight Motor Circuit — Operation and Repair

This procedure is based on the headlight motor circuits in 1983 and 1984 model 944s. The theory of operation and repair methods are the same for later 944s; differences for 1985.5 and newer are noted where applicable.

Components

• Motor — drives the headlight concealing mechanism
• Worm gear / Rotary switch — three brushes ride on a conducting disk; the inner brush has a cut-out that interrupts current when the headlights reach the OFF position; the outer brush has a cut-out that interrupts current at the ON position; the center brush has an uninterrupted path
• Relay — normally-off; controls the motor using the Red/Blue conductor
• Four conductors: Control wires — Grey, Red/Green; Supply wire — Red/Blue; Ground wire — Brown
• S1 — normally-on switch, controlled by the headlight dash switch, uses the Red/Green conductor
• S2 — normally-off switch, same control, uses the Grey conductor
• Dash Light Switch — controls S1 and S2

Theory of Operation

Starting state: Ignition on, headlights off. S1 is closed; the Red/Green conductor carries 12 V. The inner brush of the rotary switch is on its cut-out. No current flows to the relay coil — relay open, motor off.

Turning headlights on: The dash headlight switch moves to ON. S1 opens (no effect). S2 closes — the Grey conductor rises to 12 V. The outer brush of the rotary switch allows current to energize the relay coil. The relay closes, connecting Red/Blue to the motor. The motor runs until the outer brush reaches its cut-out, interrupting the relay coil current. Motor stops. Headlights are in the ON (raised) position.

Note: The first position on the headlight switch turns on parking and license plate lights only. The second position turns on the headlights and energizes the concealing motor to raise them.

Turning headlights off: The dash switch moves to OFF. S2 opens and S1 closes. The Grey conductor drops to 0 V; Red/Green rises to 12 V. The inner brush of the rotary switch energizes the relay coil. The motor runs until the inner brush reaches its cut-out. Motor stops. Headlights are in the OFF (concealed) position.

Note: If you attempt to raise the headlights manually by turning the knob on the motor, the system will automatically return them to the closed position once S1 is made. To raise headlights manually without triggering the motor, remove the headlight motor fuse first: Fuse 1 on the Auxiliary Fuse Panel (early 944s) or Fuse 2 on the Main Fuse Panel (1985.5 and later).

Notes for 1985.5 and Newer Models

Item	Change
Grey control wire	Now Yellow/Blue
Control wires	Now fused
Red/Green wire fuse	7.5 A in holder no. 16
Yellow/Blue wire fuse	7.5 A in holder no. 37
Red/Blue supply wire fuse	25 A in holder no. 2

Check all three fuses before beginning any repair on 1985.5+ cars.

Maintenance

• Check fuse values. Early 944s: 16 A in Auxiliary Fuse Box position 1. Later cars: the three fuses listed above.
• Manually cycle the motor. Remove the motor fuse, then turn the manual control knob through one full open/close cycle. Note any points of excessive resistance — these usually occur where the headlight assembly passes through the bodywork.
• Check for binding. Foreign material may need to be removed. Small adjustments to the linkage are possible at the sheet-metal tabs above the radiator on each side of the car (three small cap screws per tab).
• Check for body damage. Folds in the body metal from front-end impact may rub on the headlight housings during travel. Consult a body technician if this is preventing proper operation.
• Grease the ball-joints. Apply lithium-based grease to all ball-joints in the headlight linkage. Proper lubrication makes a substantial difference in motor load.

Repair Procedures

Headlights Too Low or Too High

Start the car and turn on the headlights. Unscrew the linkage from the motor shaft without rotating the shaft. Reposition the headlights manually while holding the disconnected linkage. Reconnect the linkage to the motor shaft. Cycle the headlights on and off once to verify position. Repeat if necessary.

Headlights Turn On But Do Not Move

Check all fuses. On 1985.5 and later cars, check the control wire fuses as well.

Remove the headlight motor assembly from the car. Disconnect the 4-pin connector and check voltages on the conductors:

State	Brown	Grey (or Yellow/Blue on later)	Red/Green	Red/Blue
Ignition on, lights off	0 V	0 V	12 V	12 V
Ignition on, lights on	0 V	12 V	0 V	12 V
Ignition off, lights off	0 V	0 V	12 V	12 V

If voltages are not as shown, the fault lies in the headlight relay or dash switch. Remove and test with an ohmmeter. Check conductor continuity. If voltages are correct, the motor assembly needs bench testing.

Bench-Testing the Motor Unit

Remove the Unit from the Car

1. Disconnect the motor shaft from the linkage.
2. Remove the 4-pin electrical connector from the motor assembly.
3. Remove the three screws holding the unit to the car.
4. Remove the rubber covers from the motor assembly.

Visual and Electrical Inspection

Check relay contact points. If burned, file the points or replace the relay.

Check relay coil continuity with an ohmmeter. The relay coil resistance is approximately 65 Ω. No continuity indicates a broken coil wire — replace the relay.

Remove the relay block from the motor if the above checks are satisfactory.

Check the 4-pin connector (male and female) for damage.

Check wiring of the relay block:

• Terminals 1 & 3: To motor and Red/Blue
• Terminals 2 & 5: To relay coil, from ground and center brush on rotary switch
• Terminal 5: No connection

Check the Rotary Switch

Remove the rotary switch cover and inspect the brushes. If a brush is damaged, de-solder it from the external wire. A replacement brush can be fashioned from a piece of flat brass. The current through these brushes is negligible in normal operation, so precise construction is not critical — only the length matters.

Test the Motor

The motor is the least likely component to fail. Remove the motor relay from the relay block by prying gently with a screwdriver. Connect one motor terminal to the positive terminal of a battery or charger and the motor case to negative. If the motor does not run, check for a poor connection; otherwise, replace the motor.

Repairing Split Rubber Boots

The rubber boots protecting the headlight motor may split at their seams over time. To repair:

1. Clean and lightly sand the areas around the split.
2. Apply tape to the inside of the split to hold the boot together.
3. Apply several layers of automotive GOOP to the outside of the split, allowing each layer to dry before applying the next.
4. Remove the tape and apply layers of GOOP to the inside of the split.
5. Trim off any excess. The repaired boot must withstand stretching during reinstallation on the motor.