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  #1  
Old 01-24-2013, 05:54 PM
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Neutral Safety Switch Troubleshooting 84 300D

I was having no Starter Motor Cranking issue.
Another Member had posted this info: Above the accelerator pedal is a 4-wire plug with a harness that runs down to under the accelerator pedal and to the transmission tunnel. Unplug it, jumper across the two purple wires in the female plug and try to start again. If it starts, you need a NSS.”
However, the Instructions will tell you if your Neutral Safety Switch is bad but not if it is the Ignition Switch causing the problem.
But, I had never seen that connector or actually done the test.
Pic one shows where the Neutral Safety Switch and the Backup Light Connector is located.
Pic 1 one the location of the Connector.

Pic 2 is a close up of the Connector

Pic 3 is the Connector unplugged, the female part of the Plug goes to the Ignition Switch. So you want to jumper the 2 of the female holes but you cannot tell the holes you need.

Pic 4 In this pic the Yellow Arrows point to the Holes that the Jumper Wires need to go into (bypassing the Neutral Safety Switch) .

If your Starter Motor Cranks you know your Neutral Safety Switch has issues.

If your Starter Does not crank this test still does not tell you if it is the Neutral Safety Switch or the Ignition Switch.

Next you want to see if the Neutral Safety Switch is making contact in Park or Neutral. You can use an Ohm Meter or a Test Light that has Batteries in it. You put the Shifter in Park and probe the 2 male connectors that have the Purple wires going to them. If your Neutral Safety Switch is making contact your Test Light will Light and/or your Ohm Meter will show that you have a connection.

If your Neutral Safety Switch is making Contact and jumper wires on the Connector did not allow the Starter to crank you likely have a Ignition Switch problem.

Unfortunately I found out that what appears to be an Ignition Switch issue can be an issue with what turns the Ignition Switch.
See the below thread if you are interested in that:
Steering Colum Lock (Ignition Lock Housing) causes Ignition Switch Failure
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Neutral Safety Switch Troubleshooting 84 300D-neutral-saftey-switch-1.jpg   Neutral Safety Switch Troubleshooting 84 300D-neutral-saftey-switch-5.jpg   Neutral Safety Switch Troubleshooting 84 300D-neutral-saftey-switch-6.jpg   Neutral Safety Switch Troubleshooting 84 300D-neutral-saftey-switch-7.jpg  
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Last edited by Diesel911; 01-24-2013 at 06:10 PM.
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Old 01-25-2013, 01:49 PM
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Does anyone know if the wrong wires are wired up, will that drain a battery ?
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Old 01-25-2013, 02:45 PM
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Quote:
Originally Posted by greazzer View Post
Does anyone know if the wrong wires are wired up, will that drain a battery ?
If you are speaking of the 240D converted to the Manual Transmission? And, it has the Same Connector if the 2 Purple (Violet) wires on the Female Electrical connector were connected together that would remove the Neutral Safety Switch from the Circuit and the Starter Solenoid sould be now be connected direct to the Ignition Switch.

Any, Electrical current going through that Circuit would be coming from the Ignition Switch.
The Manual Transmission Back up Light Switch would need to be wired to the front 2 Wires on the Female Connector but there Might already be a Connector that just plugs into it.

I can't see anything in the old NSS Circuit that would cause a Battery Drain except if the Ignition Swich was allowing some current to go though it.
If the Ignition Switch was allowing Current to get through whe you disconnect the Wire from the Smallest Terminal on the (it may also be Purple or Violet) Starter Solenoid and put one probe of the Digital Volt Meter (set on VDC) and another probe to ground you would show Voltage when there should be none.
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Old 01-25-2013, 02:55 PM
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Yes, it is a 240D. Not sure of the year, which is a sad commentary on me right now. I grabbed that 4 pin connector at the JY and I am going to solder a jumper in place instead of the wires under the car. I have no back up lights yet as I am looking for the 2 prong pigtail that goes to the shifter. The battery sat outside in some cold weather for 6 weeks and it fired up the car no problems this past weekend. The battery is new so I doubt the battery is the problem. Now, deader than a door nail. I also had a 6 plug connector under the dash and one pin fell out during the conversion. My clock doesnt work so I am thinking that pin had something to do with it. I think the wire was green. The real problem is that I am a total dummy when it comes to electrical stuff. After I melt and burn something a few times, then I will understand and get it. I got this weekend to tinker with it, however.
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Old 01-25-2013, 03:18 PM
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Quote:
Originally Posted by Diesel911 View Post
....
If your Starter Does not crank this test still does not tell you if it is the Neutral Safety Switch or the Ignition Switch.

.
You can still figure out if it's your ignition switch if you take your test light and ground pin #3 on the block with the light and turning the ignition to see if it lights up. It doesn't, then it should be your ignition switch.


Edit: As Diesel911 pointed out, this test is made on the female block. Not the male plug with the pins.
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Last edited by DeliveryValve; 01-26-2013 at 12:21 AM.
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Old 01-25-2013, 08:23 PM
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Originally Posted by DeliveryValve View Post
You can still figure out if it's your ignition switch if you take your test light and ground pin #3 on the block with the light and turning the ignition to see if it lights up. It doesn't, then it should be your ignition switch.


.
Thanks I never looked at the Wiring Diagram.
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Old 01-25-2013, 10:07 PM
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Jumper Would this Work ?

Looking at the 4-prong plug, would this jumper work ? If so, this gets rid of wires under the transmission tunnel. I am still looking for the back up light plug which goes on the shifter. I need to find one of those at the JY. I assume the other 2 holes go for the back up light ? If so, then that would seem simple to run a wire to this plug as well.

BTW--although this might be old news, those metal prongs are actually very clever items. There is a hole that runs through them where one can run the wire and a dap of solder at the top.

This jumper would connect the violet wire with the violet wire with the white line.

Thanks !
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Old 01-26-2013, 12:34 AM
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I can't tell orientation by the picture, but if holes #3 and #4 are jumped, it will work. Hole #3 is ignition switch start position power and hole #4 is the starter solenoid kick on.
Hole #1 is switched power and #2 is reverse lights. You can harvest a wire connector for the shifter switch from a wire leading from the relay box on the driver side wheelwell to the firewall.


.
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Old 01-26-2013, 01:58 AM
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Mybe this Pic will help, I numberd the holes/sockets.
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Neutral Safety Switch Troubleshooting 84 300D-neutral-saftey-switch-7b.jpg   Neutral Safety Switch Troubleshooting 84 300D-neutral-saftey-switch-9.jpg  
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Old 01-26-2013, 07:58 AM
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Quote:
Originally Posted by DeliveryValve View Post
I can't tell orientation by the picture, but if holes #3 and #4 are jumped, it will work. Hole #3 is ignition switch start position power and hole #4 is the starter solenoid kick on.
Hole #1 is switched power and #2 is reverse lights. You can harvest a wire connector for the shifter switch from a wire leading from the relay box on the driver side wheelwell to the firewall.


.
The shifter has a 2 prong deal, which looks a lot smaller than the type pictured. I am assuming that if my jumper works, then the 2 remaining holes/prongs go for reverse lights. Right now, that is not hooked up. I am thinking that the 2 prong plug for the shifter is somewhat unique, only from a manual.

Right now, it is brutally cold outside ... at least by S.C. standards. I got about 1/16" layer of ice on the cars, so I am thinking no outside work on the cars until after noonish so it warms up a bit. The battery has been charging since yesterday 8 am-ish, so it should be good to go. I am thinking that the 6 prong plug that jumped a wire during re-assembly might have something to do with my electrical issues. I have no dome lights and no clock and they should be working.
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Old 01-26-2013, 10:20 AM
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Quote:
Originally Posted by greazzer View Post
The shifter has a 2 prong deal, which looks a lot smaller than the type pictured. I am assuming that if my jumper works, then the 2 remaining holes/prongs go for reverse lights. Right now, that is not hooked up. I am thinking that the 2 prong plug for the shifter is somewhat unique, only from a manual.

....
The 2 prong connector is not unique actually. It is a standard Merecedes plug of that era. As I stated earlier, you can harvest that plug( and wire) between the firewall and relay box. See this pic, it's in this area that I marked "temperature wire connector" for another thread.




.
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Old 01-26-2013, 10:28 AM
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OK, I will grab one and size it up. I have a spare five speed shifter so I can tinker in the warmth of my kitchen to my wife's chagrin ... LOL.
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