But if it always starts when the fender terminals are bridged it can't be the battery or cables, right?

There's reasonable room to R&R the NSS in a 126. You might as well replace the shift rod bushings while the NSS is out. Make sure the NSS tab is in the same position as the old one or you'll need yet another replacement. Ask me how I know :/

Sixto
83 300SD

If there is no spring back to the key would that indicate a bad starter switch? Can the starter switch be purchased separately? Can the switch be tested with the instrument cluster removed?
The steering lock unit was replaced four years ago and I sure don't want to go through that.
Thanks again

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

Funny, I'm fighting through the same problem on my SD. Exact symptoms.

I can jump it by directly powering the solenoid. After I do that it starts behaving and works without the key for awhile. A day later back to click with the key. I put a meter on the solenoid wire in the little screw terminal box and it said 0.3 V when I cranked (or clicked it ). So like Gears I thought I was getting "no power".

But the fact there was some signal means that something was happening. The NSS isn't totally cut off.

Sorry to hijack but it's odd I'm getting the same problem at the same time in almost the same car. Must be the moon.

I checked the voltage on the purple wire coming out of the ignition switch and it jumps up to a nice 12v when I click the key over to start. So that appears to be good. Used the sewing pin through the insulation trick.

I have an NSS on order to plunk in. My NSS has an odd history. I just had my tranny R&Rd. In July. So the ground wire was taken off. I also noticed the tranny shop used my old (URO or Febi cheap NSS) I replaced last year - I marked it. I heard the cheap ones suck lately. I was dumb to use that. My bushings were replaced one year ago at the time I swapped the NSS.

The other smoking gun is the low voltage at the solenoid. Should I see 12v here when I turn the key? That may mean a short in the solenoid or a weak connection in my NSS or the downstream wiring.

The fact this started happening right after the tranny rebuild suggests the NSS got bonkered by the techs or, as SD BLue keeps repeating, something is crazy with the ground strap.

The fact that it starts ok when I jump the solenoid to 12v makes me think the ground strap is okay...but it was the last thing somebody messed with along with the NSS. I'm going down there to unscrew and clean that tomorrow.

Sorry to hijack but it looks like we have the same problem. I'll let you know what I find Gears.

Btw - worst possible is I swap out my Junk Chinese NSS or I swap starter. I actually found your thread while looking for starter swap info. The solenoid could be flakey.

You're tackling this at 81? You're my hero.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

Yes...I did that too. That's why I'm using the cheap NSS to replace my OE one. After the car wouldn't start I came in here and read the very good thread by (forgot his name the crazy guy who changes AC evaporator for fun). I couldn't believe it was so easy to destroy that switch.

I'm just hoping I don't have to replace the starter. The ability to jump the car with a 12v to the solenoid every time suggests I won't have to do that. So that leaves ground strap and NSS.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

You hear "a click", that is one click, which is very different than click, click, click, which is 3 clicks that the OP described in the subject title.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Spring back function for the key is located in the electrical switch.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

There are multiple contacts in the NSS. Park, reverse, neutral maybe separate contacts. Just because reverse contact is ok does not mean park and neutral is also ok.

If you want to jumper the NSS, best place to do it is at C146 above the accelerator pedal (pins 3 & 4 of 4 pin connector, 2.5 vi/wt and 2.5 vi)

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Ok. I get one click. I'm pretty sure it is the solenoid clicking. Weak click. Not the solid "CLACK"! When it makes the connection and turns the car over. Just more of wimpy "click".

I've jumpers the screw terminals on the firewall to a pushbutton on the end of a wire in the car. I fused the circuit for safety and noticed I burned a 5A, 10A fuse while hitting the button. I put in a 25A and it works now. I started out with some wimpy 2A pushbutton a too and they didn't work. They didn't carry enough current. I finally put a 15A switch on that works. What I'm getting at is this thing carries a lot of current.

It is either malfunctioning (shorted) or it was designed to have a big draw. Funny doing it this way through the ignition switch but maybe that is why MB uses that beefy switch. All this is pointing at a bad NSS on my car. The fact it fires when jumpered gives me hopes I won't have to replace the starter which looks like an ordeal.

I'll get my new NSS in a few days. I really wanted to try to break and bypass the circuit at C146 but I cannot seem to find it. I've tried following the purple wire from he ignition switch but I get lost under all the wrapping. So that is why I poked the insulation at the ignition switch and found 12v when I put the key in the start position.

The harness down at the NSS is pretty sealed up and hard to poke into.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

Hi Funola. Thanks for your great info. How do I access the C146 above the throttle pedal. Were do you get that number from? Wish I had your info and now how

__________________
1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

A weak click indicates the solenoid is not getting full current to pull in all the way, so the centrifugal clutch did not engage and no power was applied to the starter motor. Could be a bad NSS or could be the wiring anywhere in that circuit, starting at the fuse to ground.

As I recall, the starter solenoid should not draw more than around 7 A. If you are blowing a 15 A fuse, there is a fault somewhere. That much current may be exceeding the rating of the ignition switch. You should try to sort that out

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Info is from the electrical trouble shooting manual of the FSM. You have to take the knee panel off to access C146. If you go to the key switch and follow the 2.5 VI/WHT wire, it should go to a single pin connector, then to C146

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

If you find C146 on your W126 SD post a photo. I'm still looking for it. I cannot find any plug with a vi/w wire.

Tonight my remote switch stopped working. I can still start the car by jump wring the screw terminals on the firewall no problem.

I decided to pull my ground strap and give it a good inspection and cleaning. It was pretty dirty and I got the terminals and washers nice and shiny. No luck. Same click issue with the key and remote switch.

As for the remote starter button my guess is the 10' of #16 wire is too much resistance a long with the fuse and switch contact resistance. The 1" jumper wire (a banana Jack) works fine on the screws.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

That's what I'm afraid of. Thanks for the reality shot. It's crazy current for the NSS and ignition. Good point. I may just burn up a new NSS if I just plunk it in.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

My experience has been that a faulty solenoid gives you several clicks. However a single click has always been a weak battery.

Sorry, There was no year/ model in the title so I falsely assumed it's a 300D. For 84 SD the info is not that different. C146 is a 6 pin connector in driver's foot well to the top right of the accelerator pedal.

NSS is on C146:
2.5 VI/WT pin 5

4 VI pin 6.

2.5 & 4 is the gauge of the wires

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked