Description of 1950 Buick Lighting Switch

The first Series 1,.0 cars use a lighting switch which does not control the map and instrument panel lights; these lights are controlled by separate switches. Later Series 40 and all Series 50-70 cars use a lighting switch which incorporates a manually operated rheostat for controlling the map and instrument panel lights, thereby eliminating the separate switches for these lights.

Both lighting switches are “push-pull” types operated by a knob marked “LIGHTS”. Three “push-pull” positions of the switch knob provide control of the lights as follows:

  • “Off” position (knob all the way in) cuts off all 1950 Buick lights controlled by the switch.
  • “Parking” position (knob pulled out to first notch) turns on the parking lights, tail lights, and license light. The map and instrument panel lights also will be turned on if the controlling switch (1st Ser. 40) or rheostat is set for these lights.
  • “Driving” position (knob pulled out to last notch) turns parking lights off and turns headlights on, while the other lights remain as in the “Parking” position. The headlights will be on the “upper” or “lower” beams depending on the position of the separate dimmer switch.

The knob of the Series 40-50-70 lighting switch must be rotated “to control the map and instrument panel lights. With knob turned all the way counterclockwise these lights are off. Turning the knob clockwise the first step turns on the map lights only, the second step turns on the instrument lights and leaves map lights on, the third step turns map lights off and leaves the instrument lights on; further turning of knob clockwise reduces the brilliance of instrument panel lights.

Description of 1950 Buick Thermo Circuit Breaker

A thermo circuit breaker is incorporated in the lighting switch assembly, to protect wiring from damage due to short circuits in any lighting circuit controlled by the switch.

The thermo circuit breaker consists of a bi­metal blade and set of contact points connected in series with the lighting circuits. An abnormal flow of current through the circuit breaker, such as would be caused by a short circuit in a lighting circuit, heats the bi-metal blade sufficiently to separate the points and cause them to vibrate. The vibrating blade alternately opens and closes the circuit, thus reducing the flow of current and protecting the wiring against overheating and burning. The flickering light produced by the vibrating circuit breaker serves as a warning to the operator of vehicle that a short circuit exists.

Test of 1950 Buick Lighting Switch

If the lighting switch is suspected of being faulty, the contacts can be tested by connecting a short jumper wire between No.1 terminal and the other terminals while observing any change in the brilliance of lights affected.

With switch in “Parking” position (first notch out) connect jumper wire between No. 1 and No. 2 terminals and note change in parking lights. Bridge between No. 1 and No.3 terminals and note change in tail lights. With switch in “Driving” position (last notch out) bridge between No. 1 and No. 4 terminals and note change in headlights.

If no change in brilliance of 1950 Buick lights is noted the switch contacts are satisfactory and the cause is in the wiring circuit connections or lamp bulb. If switch is faulty it must be replaced since internal repairs cannot be made.

Replacement of 1950 Buick Lighting Switch

  1. Disconnect ground cable from battery and disconnect wires from lighting switch.
  2. Loosen knob retaining set screw with a 3/32″ Allen wrench and remove knob from rod. Remove switch mounting nut with Wrench J 1589 and remove switch from panel. See figure 10-81.
    1950 Buick Lighting Switch-Series 40-50-70

    1950 Buick Lighting Switch-Series 40-50-70

  3. On first Series 40 switch, control rod may be removed by depressing the retaining spring. On the Series 40-50-70 switch, pull rod out as far as possible, insert stiff wire into small hole in switch case to depress the catch and pull rod out. NOTE: Knob and rod may be removed as a unit in this manner before removal of switch.
  4. When installing lighting switch, connect wires according to color codes as shown on chassis wiring circuit diagrams in Section 10-J. When connecting battery ground cable use care to properly wind the clock (par. 10-21, e).

Test of 1950 Buick Thermo Circuit Breaker

To test the thermo circuit breaker, remove lighting switch from instrument panel to avoid possible damage to adjacent instruments.

Since the current required to open the circuit breaker contacts depends somewhat on outside temperature, the circuit breaker should be tested at normal temperature (70° to 80°F.).

  1. Connect an ammeter and a carbon-pile rheostat in series with the No. 1 terminal of lighting switch and positive terminal of a 6- volt battery, and set rheostat to provide maximum resistance. Rheostat must have capacity for 42 amperes and be adjustable down to .14 ohms.
  2. Connect the protected (not numbered) terminal of lighting switch to negative post of battery.
  3. Adjust rheostat to give 42 amperes. The circuit breaker should start vibrating in three minutes or less.
  4. Adjust rheostat to give 30 amperes on ammeter. The circuit breaker should remain closed indefinitely at 30 amperes.
  5. If circuit breaker does not operate as specified the lighting switch assembly should be replaced. The circuit breaker is not adjustable and no attempt should be made to alter the calibration by bending the bi-metal blade. The contact points must not be filed or sanded.



1950 Buick Headlamp Assembly

The headlamp assembly on each front fender consists of a body, wiring, connector, mounting ring, sealed beam unit, retainer ring, door and gasket. See figure 10-82.