Corvette Headlight Motors. . . . .
The concealed headlight on the 1963 to 1967 helped give the mid-year Corvettes those smooth beautiful lines they are known for. Small electric motors with a gear box are used to raise & lower the headlights. Nine out of ten times the problem with a motor not working or working slowly is the main drive gear in the gear box. The picture below shows an excessively worn gear. There are two reasons for this problem. First the headlight bucket assembly has to rotate freely. Corrosion with the steel pivot shafts and the brass bushings will cause binding in the bucket assembly. The main reason for drive gear failure in basically a design flaw. When the headlight up/down button is pressed, the bucket will open/close to the end of its travel and the motor will try to continue to turn as long as the button is pressed. There is no electrical cut-off when the bucket reaches the end of travel. The remedy is to release the button as soon as you see the buckets reach the end of their travel. ONE MORE NOTE OF CAUTION. When working with the bucket assembly or the headlight motors, NEVER use white lithium grease. This grease hardens faster than any other type of grease. A good general purpose grease will work fine.
Typical Failure Modes:
Within the headlight motor gear box is found a large aluminum drive gear which does most of the gear reduction work. In 90% of the motors, this gear is found to be worn beyond repair, (see examples below). This is usually caused by the headlight door pivots at one time being frozen so tight that the motor could not open the door. Also if the up down button is still pressed after the bucket is fully opened or closed, the motor still tries to turn and the gear will eventually fail. If a gear is not too badly damaged, it is possible to rework the teeth by filing the O.D. and teeth slots smooth. It's usually a good idea to replace this gear with motor restoration. Replacements are still available from G.M. or a reproduction is now available at half the price.
The second most frequent cause of motor failure is the field coils within the motor portion are burnt out. Many times a motor will work in one direction and not the other. Normally burnt field coils are to blame. The main reason for these burnt field coils is that someone installed a too long of a motor-to-support retaining screw which screws right into the fields and shorts them out. Maximum length of the mounting screw is 5/16". Look for brown/black heat marks on the white insulation cloth, (see example below), for overheated coils. The field coil case can not be purchased separately. It can be repaired but adds substantially to the cost of restoration.
Note brass bushing in bottom of field case held in position by steel fingers
Headlight Motor Disassembly Cautions:
The field coil case is separated from the gear box by removing the two long 1/4" screws. The armature should be removed to be cleaned and polished. The commutator where the brushes run should be "trued up" on a lath and polished with 400 grit paper. Many many times you will find that the brass bearing assembly, which supports the armature in the housing, is frozen to the shaft of the armature. This is caused by the galvanic corrosion of the dissimilar metals. Care must be taken to remove the armature without removing the brass bearing from spring steel retaining clips inside the field case housing. The best trick that I have found is to place the case housing/armature assembly in a vice with the bearing end up. Use a 3/32" drill to drill thru the case into the brass ball just deep enough but don’t hit the steel shaft. Remove the drill from the drill motor, turn the drill around, (see photo) and place it in the hole you have just made. Soak the ball and shaft with penetrating oil and let it set for a little. When ready, use a screwdriver blade to turn the armature shaft. The drill should hold the brass ball in place and allow the shaft to turn independently of the ball. Make sure there are no burrs on the armature shaft end where the manual open disk fits onto the shaft. The shaft should now slide out of the brass bearing and field case housing leaving the bearing in the field case.
Using a drill to free frozen Brass Bearing
Armature with Brass Bearing Frozen to Shaft
Burnt Field Coil
5/16” max. Length screw
** CAUTION **
When installing the headlight motor, BE SURE to use a mounting screw and lock washer combination that is not over 5/16” long max. To use a longer screw will short out the field windings and burn out the motor.
When the headlight motors are assembled, there are no markings to tell the left from the right hand motor. The foot is marked as shown below. If you’ve mounted the foot on to the motor and have the offset angle as shown in photo #2, you have the foot on the wrong motor.
1963/1967 Headlight Motor
Front Bracket (“Foot”) Assembly
Photo #2 - Wrong foot on motor
Photo #1 - Correct