Mercedes-Benz Ponton Ignition Switch Repairs

This article describes how to repair your Mercedes-Benz Ponton ignition switch without following the directions in the Service Manual (Job 15-21).

My switch was failing; sometimes the car would start and run normally. Other times, the generator light would barely glow, and pressing the starter button would make the light go out. The car would stall at times, and no generator light was showing. This was caused by high resistance, and slightly burned contacts in the ignition switch. The Service Manual suggested removing the whole steering column bracket and lock assembly before servicing the switch. I was able to service the switch without removing those parts.

 

Figures 1-2. Exploded parts diagram: Table 28 / Steering / Group 46

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Figure 3. Ignition switch cover (77) under the dash. Note: Job 15-21 refers to this as the "contact cap."

There should be a round nut (80) that keeps the cover on the back of the switch. Removing the round nut allows the cover (77) to slide rearward on the wires – providing access to the screws for the wires.

Figures 4-5. Removing the Bakelite contact cap (77)

The ignition switch retaining screw (79) is loosened with a 6 mm hex wrench. After the wires and retaining screw are loose, move the switch (76) toward the front of the car about 1/4” to clear aligning pins and engaging pin.

Figure 6. Ignition switch (76) contacts and tubular bulb (81)

Update: February 11, 2016: The current M-B part number for the bulb is 072601-012140. They have to be ordered, but any dealer can get them. They are stocked in the U.S.

Figure 7. Ignition switch (76)

Figure 8. Ignition switch (76)

Table 1. Ignition switch terminals

Figure 9. Ignition switch terminals 61, 30, 15 and tubular bulb (M-B part number 072601-012140)

Revision C Accessing the Ignition Switch on a Type 220S Sedan

The following excerpt is from the International Ponton Owners Group (IPOG) forum on May 5, 2021.—Ed. Gentlemen, I am trying to access the ignition switch in the steering column. Can you please advise me on how to remove the wood trim indicated in the photo? I do not see any screws holding it. Thank you, Dilan Perera Victoria, Australia 1958 220S (RHD) Figure 10. Type 220S (RHD) dash wood removal to gain access to ignition switch. Hi Dilan, Removing the wood is usually only needed for removing the whole steering lock assembly. In any case, the first thing to do is loosen the steering column clamp so the column drops a bit. This will allow space to take the wooden piece out. You have access to a screw (or screws) fixing the wood to the top of the dash, via the little door on the right of the steering wheel. The screw is just above one of the knobs. There are two other nuts on the bottom left. Here is a photo of a spare part. Jeff Jacobs Cape Town, South Africa Figure 11. Example of Type 220S sedan (RHD) dash removed and mounting screws. You do not need to remove the wood trim to get the switch out! Work through the radio and instrument cluster openings. Charles Taylor Falls Church, Virginia USA There are metal brackets at the bottom of the wood that are attached with screws to the metal piece beneath the dashboard. You unscrew them from underneath allowing the wood panel to be removed. Dan Diamond Toronto, Canada