Replacing ignition key assembly - PeachParts Mercedes-Benz Forum

cmac2012 · #1 10-19-2018, 02:56 PM

Oh man, the ongoing metal fatigue blues. I noticed a few times in the last week that it's getting sensitive, I'll do the normal routine and turn, then nothing. I'll turn it all the way to off and try again and it starts.

Yesterday on a 700 mile journey it starting doing it quite a bit. Yikes. No mega-fail yet, no prolonged 'cannot start.' Would like to pre-empt that. Not being able to start far from home would be unpleasant.

Anybody swapped this out? I'm finding some good prices on the web for a Filstein part, key and tumblers but I think my problem is deeper than that.

I'm guessing a lot of the matter goes on with this part:

https://tinyurl.com/y78j3lzf

Not wishing to bring up a competitors name here but I haven't found the part yet at Pelican. - Wait, just did:

https://www.pelicanparts.com/More_Info/1264620730.htm?pn=126-462-07-30-MBZ&gclid=CjwKCAjwgabeBRBuEiwACD4R5h0FE3f550kpJur98rtASpqCK0gyiLYW4G8SnkgABp5S2eMRlM7TMBoCAsYQAvD_BwE

Found this good article that confirms what I more or less knew: the time to renew is while it's still mostly working:

https://tinyurl.com/y7xg2rta

Diseasel300 · #2 10-19-2018, 03:01 PM

The key part is just a lock. If it isn't jamming or failing to turn, it's fine. The part that will be giving issues is likely to be the electrical switch part behind the key lock.

Make sure you don't have neutral safety switch issues first. The switch can be worn out or the shifter bushings may be toast. Either will prevent the starter from doing *ANYTHING*.

cmac2012 · #3 10-19-2018, 04:30 PM

That is a very good point. I had that problem in my Chevy van once.

And now I'm in hotter water than before, just tried to start it, no can do. I'll go out again and jiggle it in neutral and park while trying to start.

Update, no jiggling works, the ignition process feels different, something weak in the last final push. I was thinking that if I'm going to dig into it I might just buy the new tumblers while I'm at it. Only about $22. But yeah, I agree, that's not the problem here.

I went to Kent's tutorial on starting issues, it starts fine by jumping the contact on the starter, lucky for me that contact is easy to reach. On some cars you'd be jacking it up to get under. I may just do that to limp back to the bay area. There I'll trouble shoot the neutral switch. I've got a keyless entry fob, I'll just leave the sucker running and locked ... and not unattended for longer than a few minutes.

Diesel911 · #4 10-19-2018, 10:56 PM

If the Neutral Saftey Switch is no good or there is other issues in that circuit the Starter will not even crank. No cranking need to be difrentialted from cranking but not starting.

If this is the 86 300SDL and when you turn the Key it is not feeling right it could be the innards of the Steering Colum Lock which is between the Lock Tumbler and the previously mentioned Ignition Switch.

Don't wait until your tumbler and other parts cannot turn or you won't be able to remove the Lock Tumbler and the Steering Colum Lock and even the Ignition Switch has to have the Lock Tumbler in a specific position to remove the Electrical Connector on it.

Also the Lock Tumbler does not have to bind up not to work. When my Tumbler failed it fell apart inside. And several years previous to that the inside of my Steering Colum Lock broke and it mimicked a Lock Tumbler Failure.

The Steering Colum Lock I got came with a new Ignition Switch and Vacuum Shutoff Switch (it mounts on the Steering Colum Lock Assembly). And as it turned out while the old Ignition Switch functioned OK the Contact Points on one side were burned off and gone. So I needed a new one.

My steering Colum Lock thread
Steering Colum Lock (Ignition Lock Housing) causes Ignition Switch Failure

cmac2012 · #5 10-22-2018, 11:27 PM

That all sounds a bit daunting. Will need to research further.

I just returned from a weekend up in the hills, just south of the Canadian border, very remote - you can see every constellation and the milky way. Only shut it off a few times, had to use jumper cables to resume - they have a little extender jaws that are perfect to grab the terminal at the solenoid pin. Got back to home base and attached some wire to a ring terminal, bolted it onto the solenoid bolt and put an alligator clip on the other end. Much less hassle. Just unclip it, touch it to the Pos terminal, and clip it back.

ykobayashi · #6 10-23-2018, 07:48 AM

Ok, that sounds like a neutral safety switch (NSS). Not tumblers. Could also be the electrical switch which is behind the tumblers in the ignition switch/lock assembly.

If your key is turning freely don’t waste the $22. There are several NSS threads here. I’ve been through it twice. Takes 20 min to drop in another switch. If you don’t do that, there was a guy here who put in a push button to start the car.

vwnate1 · #7 10-23-2018, 10:16 AM

I'll wait to hear the eventual solution .

cmac2012 · #8 10-23-2018, 12:36 PM

Quote:

Originally Posted by ykobayashi

Ok, that sounds like a neutral safety switch (NSS). Not tumblers. Could also be the electrical switch which is behind the tumblers in the ignition switch/lock assembly.

If your key is turning freely don’t waste the $22. There are several NSS threads here. I’ve been through it twice. Takes 20 min to drop in another switch. If you don’t do that, there was a guy here who put in a push button to start the car.

I am starting to pull back from the 'new tumblers' bit. Would then be a different key from the doors.

I had caught the whiff of a story which pointed out the sort of difficulty that 911 spoke of above. 20 minutes sounds great but isn't there some dash disassembly involved? That can take a while.

Here is my quicky solution for a fast jump:

Touching to ground has no effect, no surprise, that circuit is already connected to ground, just looking for some current to make its way to ground. The alligator clip keeps it where it can't get into trouble but I twisted and arranged the wire (#12 stranded) so that if I detach the clip it doesn't fly around weird - on the off chance the clip did let go.

I had a thought to install a pushbutton switch inside - would need to find a way through the firewall and then a live 12 volts under the dash. Shouldn't be too tough. A new ignition switch would be preferable.

ykobayashi · #9 10-29-2018, 11:56 PM

Quote:

Originally Posted by cmac2012

20 minutes sounds great but isn't there some dash disassembly involved? That can take a while.
e.

Umm, yeah kind off you pull the lower kick panel off the drivers side under the dash and pull the panel on the side of the tunnel. Not really dash removal. This is done to diagnose the issue ...that is to see if you have an ignition switch problem, a wiring problem or a NSS problem. I recall splitting some connectors down there and checking them with my ohm meter. The ohm readings indicated something was wrong with my NSS but the actual values were not too obvious. The resistance through the switch was low like a few ohms but it was too much to handle the current requiried to move the solenoid. I measured the current when it was all done and it is remarkably high. Probably why the NSS is so big and chunky.

20 min is how long it takes me to jack up my car, slide under and R&R the NSS. I have a 126 and there may be a bit more space along the tunnel.

cmac2012 · #10 11-05-2018, 02:52 PM

Well, I, uh ... went with the cowboy solution. Installed a temporarily-on switch (pushbutton IOW) under the dash. I went with a Gardner Bender switch rated 6 amps at 120 AC. Wasn't positive that was good enough for DC, pretty sure but did some searching and found this calculator:

https://www.batterystuff.com/kb/tools/ac-to-dc-amperage-conversion-run-through-an-inverter.html

They claim 66 amps at 12V. I didn't realize the relationship was that simple.

This was the easiest rig in which I've ever looked for and found an always hot lead under the dash. Approx above the emergency brake pedal is a terminal with two 6mm studs (IIRC) with a few ring terminals attached. As soon as I saw it I was happy as it has a number of plastic guard-like things protruding downwards to ward off contact with the bare studs. Sure enough, battery voltage at all times. Useful to know when I install my next radio/stereo in order to have always on cell charging. Need to research that, make sure I get the right kind.

Took me some searching but I eventually found the ideal point to insert the solenoid connected wire through the firewall (along side other wires).

I went this route for a few reasons: cheaper, quicker, and most attractive, will make it harder to start in the event of my leaving the keys in the ignition, which, God help me, I do now and then. Senior moments creeping in.

Diseasel300 · #11 11-05-2018, 03:08 PM

Quote:

Originally Posted by cmac2012

Well, I, uh ... went with the cowboy solution. Installed a temporarily-on switch (pushbutton IOW) under the dash. I went with a Gardner Bender switch rated 6 amps at 120 AC. Wasn't positive that was good enough for DC, pretty sure but did some searching and found this calculator:

https://www.batterystuff.com/kb/tools/ac-to-dc-amperage-conversion-run-through-an-inverter.html

They claim 66 amps at 12V. I didn't realize the relationship was that simple.

The relationship isn't that simple. That website is converting DC to AC through an inverter, not rating switch contacts.

Switches rated for AC use have different contact material, smaller points, and a narrower points gap than switches explicitly rated for DC use. Do yourself and your starter a serious favor and get a DC rated switch. The solenoid draws several amps and your AC rated switch will have a *VERY* short life before the contacts weld and leave your starter engaged against your will.

cmac2012 · #12 11-05-2018, 03:13 PM

Ah, good call. I wasn't sure about the info I was getting at that site. Seemed too simple. I was wondering if I might find myself pulling the switch out of its new home and jumping the leads at some point. I suspect I might be OK for a while. In fact, I'm pulling it out now for easier access and will keep a wire cutter handy. That way I can limit a 'starter on' scenario to a few seconds. I would imagine a 15 amper would do it. I'll look into that.

Diseasel300 · #13 11-05-2018, 03:24 PM

The info at that site was good information and is correct in the conversion of energy, it just wasn't intended for use when rating contacts in switches. Make sure the switch you use is rated for DC. A 20A contact rating or higher would be a good idea, the initial inrush amperage through the solenoid is quite high due to the pull-in coil operating. The holding coil is significantly lower in amperage.

cmac2012 · #14 11-05-2018, 04:00 PM

That occurred to me after I posted, that is that the info was good for what it was intended, just that I was hasty in my research. I just now popped into Kohlweiss, got a 30 amp DC switch for 9 bucks. My first instinct had been to go to an auto parts store, should have listened to that.

Diseasel300 · #15 11-05-2018, 07:05 PM

30A switch should be fine for what you're using it for.