Text: Douglas Broome / email@example.com
/ McLean, Virginia
Photos: Chuck Simonton / firstname.lastname@example.org / Washington, D.C.
If your Mercedes-Benz Ponton has a brake booster (power brakes) the brake light switch is screwed into the front "nose" of the booster pointing downwards. You will see a gizmo about the size of a thumb with two wires attached. The wires have ring connectors if original. The switch has threaded holes if original. Replacement switches usually have "male spade" lugs. Female ends will be found on the wires as replacements. It does not matter on which side the wires fit. They can be reversed with no problem. If you have no booster or if your switch happens not to be located on the booster, the switch will be found on the top of the master cylinder. To find that, follow the tube down from the brake fluid reservoir.
Photo 2. Power brake booster mounted on firewall with brake light switch disconnected
First verify the rest of the associated electrical system. Remove both wires from the switch. Connect them together and let them hang in the air.
Photo 3. Chuck Simonton's Mercedes-Benz Type W180 220S Ponton sedan
Turn on the ignition switch and walk to the rear of the car. Observe the brake lights. If they come on, the problem is the switch in some fashion. If they do not illuminate, the problem is in the wiring, the bulb, or the socket.
If the bulb, sockets, and wiring are operating, the switch contacts may be the culprit. Disassemble and clean them off. If that works, then fine. If that does not work, sometimes the switch can be made to operate for awhile. Remove it and clean it out with brake cleaning fluid.
Then take a drift punch (without a point) and press into the hole and depress - flex - exercise - depress the metal diaphragm inside a number of times. Sometimes limbering up this diaphragm will rehabilitate a switch for awhile. The metal diaphragm will not be punctured by the drift punch. Refit it. There is no need to bleed the brake system.
Photo 6. Replacement Mercedes-Benz Ponton brake light switch with spade fittings
If it works, this will be okay for awhile. If not, you must obtain a new or known working replacement. New replacements usually come with spade fittings, like the one shown. The current Mercedes-Benz part number for the switch is: 001-545-08-09.
Created: January 13, 2007 / Jeff Miller