Last year a mechanic advised that I would soon need to replace the electronic part on my ignition switch. I ordered the part and just never put it on. It got to where you would turn the key, glow plugs would cycle then you try to crank and nothing. I have removed the electronic ignition switch. In comparing it to the new one, they are different. I have attached a picture. The one on the left is the new one, the right the one from the car. I need to know if the new one will work or do I have the wrong part. They look the same except the new one is about 1/4" shorter than the original. it doesn't have the same white center piece. What does the white thing in the center of the original one do? Hope you can help. Car has been down about 4 wks. Need to get it going again

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It's a locking mechanism. There are a number of threads on here which talk about it. I think the replacement will work without it if my recollection of those threads is correct.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

ok thanks. will look. haven't found any specifically addressing this. I'm sure I haven't used the correct search term.

it's just a keyway to keep burglars from pulling off the wiring harness... without it, you can remove the harness in any key position... much easier to jack the car without the keyway...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Got part installed. Started car several times. Put gauge cluster in place. Started car again...Put rubber boot/cover in dash over key. Had to move ignition to get boot/cover in place....now car won't start. It is doing the same thing as before. Turn key, let glow plugs cycle....turn key to start.....nothing.

Very frustrated right now!

OK, read in another post about black box on right fender in front of battery and jumping #1 and #3. Just did that and car started.

If that was your initial symptom that the mechanic diagnosed, there are other possible causes for that besides the electric switch. Could be NSS, could be poor connections anywhere in the wiring harness. It's a pretty common problem. My TD has done it periodically in the 8yrs I've owned it. It usually happens during temperature extremes. I just keep a short piece of wire to jumper the terminals. Once I start it the problem usually goes away for 6 months or more. Some people have installed an additional solenoid in the system to rectify the problem. Someone resurrected the thread of that solution with pictures in the last day or so.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Kerry, the mechanic diagnosed it being the electric switch, because to get the ac/heat fan to come on you had to turn the key slightly back for it to blow.

I had no symtoms other suddenly you could turn the key to start the car and one time it might start then the next nothing. No extreme temperatures. No problems in 100+ temps this past summer.

It worked fine after replacing the elec. switch. I started the car multiple times while reassembling, until I shifted the whole ignition assembly to finish putting the dash back together.

I also noticed a delay in the steering wheel lock engaging.