Contact breaker Points

In the course of time, erosion occurs at the points creating a pit and build-up (material transfer). This does not normally affect operation. If the points are badly eroded, new ones must be installed.

Possible defects in the system can be determined by checking the points visually.

1 - Pit and build-up with clean contact surfaces

Normal erosion

2 - Gray contact surfaces

Breaker point gap too small and pressure too low

3 - Breaker points blue

Ignition coil or condenser defective

4 - Burnt contact surfaces

Dirty (grease)

Adjusting ignition contact breaker points (Bosch)

  • Remove combustion air blower.

  • Remove protective cap for motor and cover.

  • Turn eccentric on motor shaft against thrust washer of breaker arm until breaker arm has moved to end of stroke. Loosen locking screw on contact breaker.

  • Insert screwdriver between the two small pins on the contact breaker plate and in the slot at the end of the fixed point. Turn screwdriver until clearance of 0.016” (0.4 mm) is obtained. (Contact pressure should be about 160 grams/5.5 ounces - measure with spring balance.)

  • Tighten locking screw.


The breaker points should not come into contact with grease or oil (on the feeler gauge for example), otherwise premature wear will result.

Adjusting fuel pump contact breaker points (Bosch)

  1. Clamp nut

  2. Contact breaker

  3. Gap of 0.016” (0.4 mm)

  • Remove combustion air blower.

  • Take off blower fan and spring tensioner.


Take fan off carefully! Do not apply load of more than 500 grams (18 ounces) to motor shaft! See Chapter 1.6.

  • Take motor out of its support housing and detach motor housing.

  • Turn motor shaft until cam on gear shaft lifts breaker arm fully.

  • Loosen clamp nut and adjust clearance to 0.016” (0.4 mm) with a feeler gauge by turning the contact point. Ensure that the setting does not alter when tightening the clamp nut. (Contact pressure is about 200 grams/7 ounces.)

  • Assemble combustion air blower.

From August 1st, 1969 (Chassis # 410 2000 001) combustion air blower motors from Bosch and AEG are installed. The complete motors can be interchanged. Repairs and adjustments on the AEG motors should be carried out in principle as for Bosch motors, the only difference being the removal and installation of the fuel pump breaker contacts. Contrary to the Bosch motor on which the complete contact breaker plate is replaced, the contacts are replaced individually on the AEG motor.


Contact for fuel pump


Contact for ignition