BODY-05, Headlight Motor Circuit - Operation and Repair


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Introduction

The following procedure, written by Dave Simms, is based on the headlight motor circuits in 1983 and 1984 model 944s. Dave has also included information on how the motor circuits in later 944s differ from those of the early cars. However, the theory of operation and repair methods remain the same. I've added a few notes along the way and a different circuit diagram (with Dave's approval). We plan to expand this procedure down the road to describe how the entire exterior lighting circuit works in detail. But first, I have to figure out exactly how the bridge adapter in the later model 944 works. I'd like to thank Dave for his valuable contribution to Clark's Garage.

Clark Fletcher

Foreword by the Author

My 944 had been reclaimed from an insurance company following a vandalism claim. The car had gone to a yard where some parts had been sold from it. In the process, the wiring harness had been cut in the front of the car and the headlight motor had been sold. When I purchased the car, the headlight motor in it had come from another wreck and was not connected. The internal circuit under the relay block had been rewired incorrectly. Finally, the mechanical headlight linkage was binding and several of the cap screws were loose. Surprisingly, most of the car was fine.

So far, I have rebuilt all of the brake calipers, resurfaced or replaced all of the rotors, repacked the CV joints, fixed a number of electrical problems and cured some ills in the cooling system. I have learned that one of the most important things about the 944 is the assortment of clips and clamps that hold the various tubes, wires and hoses in place. When I got the car, the top rad hose was not clamped in place. One result was the circular-saw effect that had been applied by the alternator pulley to the hose. Cars that have seen work done by a number of different people may be subject to sloppiness in the area of what appears to be unimportant details. I'm resigned to the fact that, if I want a reliable car, the details must be identical to the way they were when the car left the factory.

All told, I am enjoying working through the various systems of the 944, checking and rebuilding them. The car is different and my work has been an education. I have strived to do every task, by the book. Restoring the car's performance and reliability is my aim.

David Simms, Kamloops, BC, Canada

1983-84 Porsche 944
Headlight Motor Circuit, Operation and Repair

Components

Theory of Operation

NOTE

If you've ever tried to operate raise the headlights manually, you probably found that when you reached a certain point raising the headlights that they automatically went back down. That's because the headlight concealing motor energizes to both raise and lower the headlights. As you rotate the dial on the motor, you also move the rotary switch. With the S1 switch closed, when the rotary switch contact is made, the motor energizes and returns to the closed position. If you wish to raise the headlights manually, you must remove Fuse #1 on the auxiliary fuse panel for early 944s or Fuse #2 on the main fuse panel for later model 944s. C.F.

Notes Regarding the 1985 1/2 and more Recent Models

Similarities & Differences Between Early/Late Models:

Maintenance Suggestions

Repair Procedures

Start the car. Turn on the headlights. Unscrew the linkage from the motor shaft without turning it. Reposition the headlights manually while holding the linkage that you just removed from the motor. Reconnect the linkage to the motor shaft. Try turning the headlights on / off once more to verify the correct position. Repeat the procedure, if necessary.

Check Fuses. On the '85 1/2 and later models, the control wires are fused too. The headlight motor assembly will probably have to be removed from the car. First, disconnect the 4-pin connector to the motor. Check the voltages on the conductors.

Bench-testing the motor unit



terminals 1 & 3: To motor and Red/Blue.

terminals 2 & 5: To the relay coil, from ground and center brush on rotary switch

terminal 5: No connection.

If a brush is damaged, it can be removed by de-soldering it from the external wire. You may be able to get a replacement from an appliance repairman or to fashion one from a piece of flat brass. The amount of current flowing through these brushes is negligible if everything is working properly. Therefore, the construction of these brushes, apart from their length, is not critical.

This is probably the least likely area of failure. Remove the motor relay from the relay block by prying gently with a screwdriver. Fit a spade-type female connector to a piece of wire and insert it into the relay side of terminal 1 or 3 (whichever will connect to the green motor wire). Connect the case of the motor to the negative terminal of a battery or battery charger and the other wire to the positive terminal. If the motor does not turn, look for a poor connection, otherwise, a new motor is required.

Clark's Garage 1998