Ignition switch or ?

[Simplemandoc]

First, I'm a neophyte at engine repairs so I apologize if this is a stupid question.  I'm assuming I have an ignition switch issue, but before performing that replacement I thought I'd check in for advice.  I recently had my 67 230SL running great for my son's wedding (trailered it down to CA).  Luckily my problems waited until I went to pick-up the car from the hotel.  The car started - but with difficulty and I had lost my instrument cluster lights.  I was followed back to my trailer by friends who reported that my taillights dimmed significantly during the drive.  I thought... "probably an alternator problem".  Trailered the car home.  When unloading the car it ran only if the key was in the "start" position, (when in the "run" position it died immediately).  At least she's light to push. The easy fix (for starting fine but not staying on when key was released to "on") was the ballast resistor .  I was going to test it but couldn't find my multimeter and just ordered the part.  Replaced it with no improvement.  Finally got some time to really check into things.  Found the meter and the battery is good (but had already trickle charged it).  Noted that the lights all work great (high/low/tail); fuel pumps works, and she starts... but nothing else works.  No radio, flashers, turn signals, heater, etc. - and she doesn't "run" after releasing the key from "start"position.  I wouldn't even bother the group with this question but the dimming lights and slow progression of the failing electrical system seemed a little "off" to me (maybe not the ignition switch) and I thought I might be missing something.  So, is it time to invest the time and money to replace the ignition switch or should I test something else first?       Thanks for considering.

[Cees Klumper]

I don't think it is the ignition switch, it sounds more like a ground or fuse or other continuity / wiring problem. But I'm sure others with more electrical knowledge will chime in shortly. The switch is a bit of trouble to get to.

[Simplemandoc]

Thanks!  Yes... seems strange to me but hopefully clicks for someone.
Brian

[stickandrudderman]

Use a test light and see if you have 12v at the "+" on the coil with the ignition switched on. No "+" = no ignition.
If so run a temp wire straight from the batter + to the coil + and try to start the car. If it starts OK now then you definitely have a switch problem.

[450sl]

Check your Masscable      the cable from engine to firewall,          this can give an array of electronic issues.

Mark

[Simplemandoc]

Thanks everybody.  Definitely the ignition switch.  Just in case I don't tackle this myself, with the temp wire I can get it to someone with a better skill set.  Any recommendations in the Seattle area?

[cfm65@me.com]

Hi Brian,
I have recently come across a similar problem on a 911 Porsche forum. The poster changed the ignition switch, the battery, etc.
Eventually he found the main battery cables, from negative to ground and positive to the starter motor, were crimped and not soldered. Slight corrosion between the cables and the lugs caused poor current flow. These were cleaned and soldered and the problem solved.
I have owned many classic and vintage cars over the last 40 years and never had an ignition switch fail, except on an E Type. Go figure.
Regards
Chris

[JamesL]

Electrical issues. On a British car.
I'm shocked I tell you. Shocked

[cfm65@me.com]

James,
Please behave.
😉😉😉

[Cees Klumper]

Well my ignition switch did go bad on the Pagoda, so it does happen. It would no longer start the engine, but its 'ignition on' position was fine. No other impacts, other than not being able to start (no other electrical gremlins).

[Simplemandoc]

I followed Stick's recommendation.  Got nothing at the coil with ignition "on", but everything works with "start".  Ran a temp wire to the coil and it runs great in the "on" position.  So it seems like it's the switch or I'm missing something.

Brian

[stickandrudderman]

I was working on a 202 c class many years ago.
It had come from another garage with some very strange ignition system problems.
It took me ages to work out that someone had disassembled the plug on the loom for the ignition switch and re-assembled with the wires in the wrong place!
As a data point; I have changed maybe 6 ignition switches on 113 in the last 40 years but, as components age, you do start to see more regular failure patterns than you are used to.

[brucenator]

Have you checked the alternator and voltage regular? If they are okay then the battery could have a bad cells giving a drain on the system.

[Benz Dr.]

My ignition switch failed in an unusual way. If I hit a large bump that shook the car the whole ignition would shut off. If I hit another bump right away it often turned on. Mostly I only had to turn the key off and back on and everything would come back to life. I obviously changed it and never had another problem since.