LOGIC: If the backup lights go on with the key on, selector in reverse, It is not logical that the park and reverse contacts won't function. I can see one not working but not both.
Is there a relay to do with an old anti theft setup that is in the circuit?
Very strange that one day it is OK and the next it won't start without the car being touched.

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1984 300SD turbo 126
"My true love"

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

X2

Check your battery - it sounds like it is struggling / not providing enough power.

The classic clicking of the starter solenoid (but no spinning of the starter motor) as mentioned above points to this.

The reason why not enough "juice" is getting to the starter could also be due to dirty contacts.

Taking it one step further: Over on BW there was a fairly recent fad of "change your battery cables as they tend to corrode inside"...

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

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)

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

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

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1984 300SD turbo 126
"My true love"

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

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 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked