Author Topic: Ignition Key  (Read 537 times)

Harry

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Ignition Key
« on: October 25, 2024, 20:07:27 »
1966 230SL

Upon returning home today from a nice drive through the mountains of East Tennessee, I noticed that the alternator light came on AFTER I had turned off the ignition and removed the key.  When I checked, the ignition had turned itself on, i.e. the fuel pump was running, etc.!  (Guess it wanted to drive some more! :))

Has anyone else had similar experience?  For the time being, I just disconnected the battery.  Perhaps of relevance, I have recently installed the 123 Distributor - but it has not exhibited this issue until today.  If the ignition switch is just "tired", I think I'd rather replace than repair.  Does anyone have any advice, including a good source for a replacement ignition switch?

Harry
Harry Bailey
Knoxville, TN
1966 230SL
Automatic

Harry

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Re: Ignition Key
« Reply #1 on: October 25, 2024, 20:09:42 »
I expect what I need to replace is the "Ignition Starting Switch".
Harry Bailey
Knoxville, TN
1966 230SL
Automatic

Pawel66

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Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

BobH

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Re: Ignition Key
« Reply #3 on: October 25, 2024, 21:45:33 »
1966 230SL

...When I checked, the ignition had turned itself on, i.e. the fuel pump was running, etc.!  (Guess it wanted to drive some more! :))

Has anyone else had similar experience?  For the time being, I just disconnected the battery.  Perhaps of relevance, I have recently installed the 123 Distributor - but it has not exhibited this issue until today.  If the ignition switch is just "tired", I think I'd rather replace than repair.  Does anyone have any advice, including a good source for a replacement ignition switch?

Harry

Hello Harry, when you say the ignition had turned itself on, did everything turn on, ie the fuel gauge etc?  if the switch was shorting everything fed from fuses 2 to 6 will work, horns, wipers, washers, cigar lighter etc.  It could be the switch, if you disconnect the connection on terminal 15 this will prove or disprove the switch.  If you still have the same symptoms, then you may have a wiring short, or perhaps a backfeed from somewhere

You won't have the door open/low fluid problem, as this wasn't fitted on 230's

Good luck
February 1965 230SL Automatic
UK delivered RHD
Papyrus white, blue hard top & hub caps
Blue soft top
Blue leather

mauro12

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Re: Ignition Key
« Reply #4 on: October 25, 2024, 21:52:17 »
This red light permanently on , even with engine off , means that the bulb is getting always a + . The question is from where ? According to your experience what is the main cause ?
Mauro Pisani
250sl 1967 5speed zf manual

Harry

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Re: Ignition Key
« Reply #5 on: October 27, 2024, 15:28:08 »
All,

Thanks for the prompt responses!  The symptoms were that when I had turned the car off and removed the key, I happened to notice that the alternator light actually came back on.  But not just the alternator light, also the fuel gage and the fuel pump.  It behaved as though the key was inserted and turned to the run position.  I was surprised that I had been able to turn the car off.  At that time, I disconnected the negative battery cable to have everything actually turned off.

Then this morning when I reconnected the cable, everything went "live" again (same issue).  I started the car but could not shut it off any longer with the key.  I left the key in the off position and pulled the coil wire to turn the engine off.  So it seems clear to me that this particular issue lies in the Starting Switch.

I see Autohaus AZ offers the Ignition Switch Contact Block for about $100.

Additional thoughts?
Harry
Harry Bailey
Knoxville, TN
1966 230SL
Automatic

BobH

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Re: Ignition Key
« Reply #6 on: October 27, 2024, 15:45:41 »
Seeing as you need to remove the switch anyway, if you intend to replace it, it might be worth opening it up to see if it's repairable, the early switches  seem to be quite simple.  Most seem to fail open circuit, so the car won't work at all, but yours is shorting somehow, so perhaps something inside is loose or broken

Maybe disconnect the wire on terminal 15 just to make sure it is the switch

There's a write up in the tech manual and the description and pictures on the attachment are really helpful

https://www.sl113.org/wiki/Electrical/IgnitionSwitch

https://www.sl113.org/wiki/Electrical/IgnitionSwitch?action=download&upname=Open%20gnition%20switch.pdf
February 1965 230SL Automatic
UK delivered RHD
Papyrus white, blue hard top & hub caps
Blue soft top
Blue leather

Harry

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Re: Ignition Key
« Reply #7 on: October 30, 2024, 16:00:11 »
It just occurs to me that this post should more appropriately be under "Electrical".  (How do I move it?)

Update:
So here are some additional observations/updates since my prior post, with the ignition switch removed.  Based on having not been able to turn the running car off and finding that the fuel gage and generator light remained on even with the car off and the key removed, I expected that terminals 30 (power to the switch) and 15 (power to the coil) were not disconnecting in the switch.  But that's not what I find on the bench.  15 and 30 do disconnect.  Here is what I find on the bench.

In the key removed position, no switch terminals (P30, 30, 50, P and 15) are continuous.  So the incoming power (30) doesn't go anywhere - as you would expect.
With the key in the number 1 position, the same is observed, i.e. no switch terminals (P30, 30, 50, P and 15) are continuous.  That is also what I would expect since the owner's manual says this position is to remove the key and leave the steering unlocked (no electrical connections).
With the key in the number 2 position, switch terminals 30 and 15 are connected, feeding 12v to the coil - as you would expect.  This position also provides power to all fuses except fuse 1, which is always powered.  (This is the position that had to be connected for what I observed to be happening.)
With the key held in the 2+ (start) position, terminals 30, 15 and 50 (to the starter) are connected.
Terminals P and P30 don't appear to be influenced whatsoever by switch position - which seems particularly odd to me since they are terminals on the switch?  I think I'm missing something there.

So, the switch nominally seems to be operating properly on the bench.  If this is the case, how was terminal 15 getting power with the ignition turned off and the key removed?

Very puzzling.

Harry

Harry Bailey
Knoxville, TN
1966 230SL
Automatic

Lorsar

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Re: Ignition Key
« Reply #8 on: October 30, 2024, 18:53:33 »
It just occurs to me that this post should more appropriately be under "Electrical".  (How do I move it?)

At the bottom of the page for this thread, do you see the move topic button?  I'm curious if the OP can do it themselves.  If not, several of us are designated as moderators and can move it for you.
Lori
1968 280SL (US)

clunker

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Re: Ignition Key
« Reply #9 on: October 30, 2024, 20:26:29 »
Lori
- I think a regular reader can not see any buttons relating to topic changes (at bottom of page)
- the creator of a thread can see only a 'Remove Topic' button
- so presumably only an admin/moderator can see the 'Move Topic' button you mention
Charles
1969 US 280SL 4-speed Red/Black
DB9 / 981 S / G300 SWB / CB750 / etc