Ignition Switch Issues

[Harry]

I copied/pasted this to "Electrical" where it more appropriately belongs.  It is based on an earlier post regarding a problem that developed with my ignition switch, 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

[BobH]

If you're satisfied that the switch isn't at fault, then you must be getting a +ve feed back to fuses 2 to 6, which are all commoned together.  Normally the only +ve feed to these fuses is via the ignition switch

I would pull fuses 2 to 6 and measure which fuse has a +ve feeding back to it, it could be a short on the wiring or on an appliance.  Once you find the fuse that's live, you'll need to trace each output cable for the culprit

Regarding contacts P and P30 (P for parking?), these should have continuity when the ignition is off, ie when the key is out or not turned, as these are the connections to the parking lights which are disabled when the ignition is on

[Pawel66]

If I may add my 2 cents:
- as for P and P30, as BobH states, they should be powered when the ignition switch is at "0", even with key out; P30 is powering door switches, clock, etc.
- as for 15 getting power with key removed - if your car has driver's door switch and brake fluid level indicator, 30 connects with 15 when the brake fluid level sensor circuit is closed (low level of the fluid, reservoir cap removed, etc.) and the door is open
- you have 230SL, so you may not have brake fluid level indicator and door switch, so you may have 15 touching 30 in the appliances where they meet, e.g. steering column switch, hazard lights witch, etc. - you can trace it as BobH described

[Harry]

I have a replacement switch coming (since I have gone to the trouble of removing the ignition switch assembly) so that should be a non-issue soon enough.

I'll check for the brake fluid indicator but I don't find that on the wiring diagram (probably looking right at it).  By door switch, do you mean the contact that turns the interior courtesy light on/off?

Thanks again!
Harry

[Harry]

P and P30 appear to be connecting correctly with the key out.  And I don't "see" a low level switch in the brake reservoir on this car.

Harry

[lpeterssen]

Dear Harry

I agree with all being said by my colleagues on this forum.  You have a back feed somewhere from T30 circuits to T15 circuits.

If you had a 250 or 280SL the first possible culprit will be a defective brake fluid sensors that are kept closed all the time, and as they share the same indicator light on the central instrumentation cluster you will have power passed from door switches (T30 circuit) to T15 when door is opened with car in the ignition off position.

That can be discarded easily by removing brake fluid terminal connector or by taking out fuse no.5

You can develop a similar procedure to trace on which circuit is happening the back feed event.

Be systematic and remove one fuse at a time from no.2 through 6, and observe when the anomalies stop happening.

Once you know which circuit is the culprit, take the wiring schematic published on this site and analyze which accessories or connectors have at the same time T30 and T15 circuit lines.


https://www.sl113.org/wiki/uploads/Electrical/1968%20280SL%20USA%20Standard%20Version%20wiring.pdf

Look for those branches and observe if you have any defective wiring on those connectors or branches that may be leading to a communication between them.

Of course when this kind of things start happening……..   it is a sure indicative that your wiring harness is in desperate need for and electric spa like the one I run.

Best regards
Eng.Leonardo Peterssen
Www.wiredoktor.com

[Harry]

Thanks again everyone.  As much as I don't particularly enjoy electrical problems, I do enjoy learning new things and nuances about these cars.  And this forum is such a powerful tool for sharing expertise and experience.

My new switch will be here tomorrow and I will get it installed just to be certain that I don't have an erratic problem there, and also eliminate that as a contributor.

I'll keep you posted.

Harry

[rwmastel]

Once you know which circuit is the culprit, take the wiring schematic published on this site and ...

If this diagram is from the Tech Manual, please just provide a link to the Tech Manual material.  That ensures that as members' status changes (paying member or not) over time, they will have appropriate access to the information.  Posting here defeats the purpose, see?  Plus, no login is required to read the forums, so anyone in the world can download our nice diagram from your post.

[lpeterssen]

Rodd:

Post modified as requested, including a link to tech manual.

Is there a non protected by copyright laws diagram that I can add on my explanations so that people can follow up better what I mean?

Best regards
L.Peterssen
Www.wiredoktor.com

[rwmastel]

I don't know if the question is copyright.  We've had a classic car dealership basically copy/paste paint & upholstery color code material right from our website to theirs without reformatting and the Group did nothing.  I'm not sure if these color wiring diagrams are copyrighted.  They did originally appear in Pagoda World before the Tech Manual, as loose inserts I believe.

Regardless, I'm just trying to keep the good stuff in the Tech Manual in the Tech Manual, so there is one more reason full members feel their paid membership has value.

[Garry]

Rodd,

There was a lot discussed and some comments to the dealer by the non American Board members on the theft of our Group's information by the Florida car dealer but the American Board members at the time were fearful of litigation and we made a call not to waste members money pursuing it.

Garry

[Harry]

I received the replacement (new) switch block and before installing, I did a bench check for continuity.  I don't find that P30 and P are continuous with the key inserted or removed.  They are continuous on the older switch block that I removed.  So I am reluctant to install the new switch block before talking to Authentic Classics (supplier) about it.  Thoughts?

Harry

[Harry]

I received the new switch, only to find out that it isn't functioning properly.  With the key out or in the "0" position, I have no continuity between terminal P and P15.  I called the supplier, they have apparently had this particular issue with these new switches (and with the body being loose through the crimp connection).

I reconnected the old switch block, removed all fuses 2 through 6, and the issue with the ignition circuit being live persisted.  I then used a screwdriver in the switch block to cycle it through the positions and it stopped misbehaving (for the moment).  So the problem is apparently the switch block itself.  I'm reluctant to install the new block since those have a known issue on working properly.  I guess I'll uncrimp the original block and look for obvious problems.  (I see the information in the Tech Manual.)

Any better ideas?

Thanks,
Harry

[Harry]

Whoa - what a contraption!  So as the key is rotated, the internal ramps and springs in the switch block lift the various sets contact points connecting them to inputs/outputs on the back piece.  This distributes power to the ignition, starter and continuously powered accessories as needed.

In order for the switch block to fail to disconnect power (30) from the ignition (15), one of those lift plates has to not be returning to the retracted position.  It is spring loaded so how that is occurring isn't totally clear unless the ramp plate is not going back to the corresponding position and continuing to hold it up.  (Seems like a long shot.)

Maybe I need to thoroughly clean everything and reassemble.  Recall that this was somewhat of an intermittent problem.

Does this sound correct?

Any further advice?
Harry

[BobH]

Seems most switches fail intermittently or completely open circuit, with no continuity between 30 and 15, so your problem seems to be unusual

Once everything inside is clean and secure, it looks like the most important thing to ensure is that the plastic connection section is securely fixed to the metal contact section, so that there is absolutely no movement at all between the two halves.  I guess with movement between them, the contacts could either fail to connect or fail to disconnect

Have a look on here, if you translate, it says the same

https://www.sl113.org/wiki/Electrical/IgnitionSwitch?action=download&upname=Open%20gnition%20switch.pdf

Some pictures of yours disassembled would be useful, particularly if you can find the problem

Disappointing that your replacement switch was faulty when you received it

[Harry]

Thanks Bob.

I lay in bed this morning considering options.  I think my best option is to replace the switch block with a new one.  To that end, the SL Shop offers one but I know nothing about them as a supplier.  All appearances from their website certainly support that they are a high quality operation - so that is an option.  (Are you familiar with them?)

Another option for a new one is the Classic Center in Irvine, California.  I have dealt with them on a number of occasions and know them to very reputable.  I just don't know yet whether they also offer this part.

A final option would be to rebuild the switch block I have and install an "interrupt switch" hidden below the dash that would break the "30" to "15" connection outside of the switch.  If the switch continued to fail internally, this interrupt would not allow that failure to keep the associated circuits powered.  The other benefit of this additional switch would be as an anti-theft device since the vehicle could not be started (or at least kept running) without this switch also turned on.

I do think my rebuild of the switch block is going to include drilled/tapped holes securing the plastic back section to the aluminum body.  I was a little disappointed in Mercedes to have ever considered a crimped connection as satisfactory because they will weaken in time (especially this many years!).

I will post some photos today, for further thoughts/advice.

Thanks again,
Harry

[BobH]

If your switch isn't worn beyond repair, personally i would overhaul that, i assume it's original to the car?  You don't know the origin of a lot of new parts available, i would think most of the new switches available probably come from the same source

The vendor experience pages are on the main menu page, you need to be logged in to see them, there is actually a review of the SL shop on there

At least you've proven it's the switch and you don't have a potentially costly wiring issue to sort out, keep us updated how you get on

[Cees Klumper]

If by 'switch block' we are referring to the pastic or bakelite part that attaches to the rear of the ignition switch, that the wiring harness plug attaches to, then I would just order a new one from a reputable dealer. I did a few years ago when turning the key no longer energized the starter, after some time this being hit or miss, and $70 and an Ebay order from a UK based supplier later it's been flawless ever since. Rebuilding the worn out old one is probably not reliable in the longer run unless you can find new internal parts (but then why not just buy all new, even if it may take trying different suppliers/batches until you have a good one).

[Harry]

Cees - thank you as well.  Do you recall who your supplier was?  I agree on trying to avoid reuse of the original switch block.  The one I have is definitely showing signs of wear.

Harry

[Cees Klumper]

Harry - sorry, no, my records are with the car in France and I'm now back in Southern California.

Ebay search just now generated lots of alternatives - possibly most or all Chinese, which can be quite high quality these days:

https://www.ebay.com/sch/i.html?_nkw=w113+ignition+switch&_sacat=0&_from=R40&_trksid=p4432023.m570.l1313

[Harry]

Thanks just the same Cees.  I had seen several offerings on EBay but I was reluctant to go that route just due to my uncertainty with the sources/manufacturers.  Unfortunately, the level of difficulty/involvement in replacing this switch makes me particularly cautious about installing a component that I am unsure about.  (It's such a pain to remove and install.)

That's why I did a bench test on the new switch I received last week before installing it, only to determine that it was defective.  When I called the supplier, they acknowledged that they had been experiencing some issues with their source supplier.  (Aargh!)

So I am in a bit of a dilemma.  I'll relook at the EBay offerings, though.

Harry

[rwmastel]

Get a price from the Classic Center, for comparison.

[Pawel66]

I was going to write that Mercedes would be the obvious choice there, even if price would be high. But I did not write it as for 230SL (A 000 462 06 93) it is NLA.... last price I have is ca $220.

But maybe it is available there in the US.

[Harry]

Those are both calls I will make this morning, thanks.  And thanks for the parts number.  I couldn’t find that on the part.