Ignition switch - PeachParts Mercedes-Benz Forum

snookwhaler · #1 03-12-2012, 08:53 PM

I sold this car a while ago and the new owner is having an issue. I'm hoping you guys can help us out.

We have an ignition switch problem. When I go to glow, the key will not go past to the "start" (spring loaded portion).

Is this a permanent failure of the switch or something that can be fixed?

Any help is greatly appreciated! I remember reading about how to short the leads over on the passengers fender well in an emergency. With the switch on, should there be power over there? It has been a while since I have messed with any of this stuff. Trying to communicate some of this over the phone is proving difficult. I plan to go over there in the morning to help him out.

shadetree77 · #2 03-12-2012, 09:03 PM

did he turn the key all the way back to the left (or even take it back out)? it will only let you go past pos II one time unless you turn the key all the way back to the left again (so you don't grind the starter by accident when the engine is running). other than that it could be a bad tumbler (likely) or the back of the ignition.

snookwhaler · #3 03-12-2012, 09:19 PM

Yea.... It is much more serious than that...

Funny thing. When He first went to start the car, he did not wait for it to glow, went to start it again and it would not start... LOL!! I explained how you have to "start over" once you go to the "start" position. After that, he was off.

snookwhaler · #4 03-12-2012, 09:22 PM

OK... I was just watching a video on how to remove the tumbler. If I remove the tumbler, I can stick a screwdriver in there and test it to see if it will go to the "start position" Right?

Jeremy5848 · #5 03-13-2012, 01:40 AM

Sounds like the anti-repeat mechanism is jammed. You may be able to take the switch assembly apart and fix it. I had one jam once when doing a reassembly. It took some fiddling (and I no longer remember the details) but I was able to get it working again.

TnBob · #6 03-13-2012, 02:09 AM

Its sounding like you need a new ignition. Dont forget to take the title and drivers license in the same name with you to the dealer. That way you can get the new ignition keyed to the old key.

snookwhaler · #7 03-13-2012, 07:20 AM

Quote:

Originally Posted by Jeremy5848

Sounds like the anti-repeat mechanism is jammed. You may be able to take the switch assembly apart and fix it. I had one jam once when doing a reassembly. It took some fiddling (and I no longer remember the details) but I was able to get it working again.

When you say the "switch" are you referring to the tumbler or the components behind the tumbler that include the steering lock and the electrical portion of the switch?

Jeremy5848 · #8 03-13-2012, 11:58 AM

Quote:

Originally Posted by snookwhaler

When you say the "switch" are you referring to the tumbler or the components behind the tumbler that include the steering lock and the electrical portion of the switch?

IIRC, the ignition lock "package" has 3 major components: the lock cylinder, the steering lock (which includes the anti-repeat mechanism) and the electrical switch. The cylinder and the switch can both be removed from the steering lock and separately repaired or replaced.

If you can put the key in the lock cylinder and turn it part way, as you described, then the lock cylinder is OK. If the glow plugs, etc., work, the switch is at least partially good. Not going into "start" means that the anti-repeat lockout has broken. It may simply be a matter of removing the lock cylinder so you can get at the parts, then putting a spring or something back where it belongs. If that can't be done, you may have to replace the entire steering lock mechanism. EPC should have a diagram that will show you how far the steering lock breaks down.

Jeremy

Beagle · #9 03-13-2012, 12:43 PM

Quote:

Originally Posted by snookwhaler

OK... I was just watching a video on how to remove the tumbler. If I remove the tumbler, I can stick a screwdriver in there and test it to see if it will go to the "start position" Right?

I would suggest you do first remove the tumbler for inspection. There is a short connecting rod about an inch long - it has a slot in one end for the tumbler and a tang in the other end that connects into the electrical switch slot.

As Jeremy says there is an anti-repeat mechanism and that is part of the electrical switch mechanism not the lock mechanism. If the key is forced without turning it back fully the tang can break off the connecting rod (most likely) or break the tang on the lock tumbler. The rod is just an Aluminum alloy die-casting and will break easily.

The connecting rod can be pulled out once the tumbler has been removed and then the electrical switch can be operated directly with a screwdriver

snookwhaler · #10 03-13-2012, 03:43 PM

Thanks a bunch guys... I made it out there this morning to have a look. Here is what I found.

The switch still has the detents in all positions. But, they are all off and do not match the mark on the collar anymore. The positions have all slightly shifted to the left or "counter-clockwise" about 1/8 of an inch. The tumbler does rotate all the way to the start position. But, the spring loaded feature of the switch is gone. All the electrics would come on, but when going to the "start" position there is no spring tension to push against and nothing happens.

I followed a video on youtube and removed the tumbler assy. and collar. With the tumbler removed we were able to get the car to start. But, there still is no spring tension to the start position.

Is the spring tension to the start position provided by the electrical portion of the switch or the steering lock? This is where the problem obviously is.

Again, thanks to everyone for the help!

snookwhaler · #11 03-13-2012, 04:06 PM

Quote:

Originally Posted by Beagle

I would suggest you do first remove the tumbler for inspection. There is a short connecting rod about an inch long - it has a slot in one end for the tumbler and a tang in the other end that connects into the electrical switch slot.

As Jeremy says there is an anti-repeat mechanism and that is part of the electrical switch mechanism not the lock mechanism. If the key is forced without turning it back fully the tang can break off the connecting rod (most likely) or break the tang on the lock tumbler. The rod is just an Aluminum alloy die-casting and will break easily.

The connecting rod can be pulled out once the tumbler has been removed and then the electrical switch can be operated directly with a screwdriver

I think this is what happened. It makes perfect sense. Should this rod be visible once the tumbler is removed? This rod is part of the electrical portion?

I need to put these guys in touch with Phil too. They accidentally broke the nipple off the check valve on the main vacuum line running from the vacuum pump to the brake booster. So, they need one of these as well.

Beagle · #12 03-13-2012, 07:15 PM

Quote:

Originally Posted by snookwhaler

I think this is what happened. It makes perfect sense. Should this rod be visible once the tumbler is removed? This rod is part of the electrical portion?

The rod is a separate part of the lock mechanism. You can get hold of the slotted head with long nose pliers and pull it out. If you look inside you will see a small pawl that operates the steer lock beside the rod head, don't pull that.

This is a common problem with these locks and what often happens is the tang sometimes does not break right off but twists so the key will not turn far enough to make contact with start. Spring tension is provided by electrical switch.