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.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles