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  #1  
Old 06-14-2008, 10:31 PM
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Odd Electrical Problem 300 TD

This evening I drove my wife and I to town in our 83 300TD. When I stopped at the restuarant to get out, the engine turned off as normal, but three of the lights on the left side of the dash lit up as well as the reserve light for the fuel tank (not low on fuel). I noticed the aux fan was also running.

I came back home and disconnected the ground cable for a second and when I did, all lights went out. Back to normal it appears but I did notice that the ground cable sparks when I reconnect it telling me that something is pulling power still. So I started the car again, then turned it off, same problem. The battery, brake and brake pad wear lights all come on after the key is turned off. Radio, A/C, etc all cuts off normally.

Any ideas out there? I suspect maybe the ignition switch itself? Or some relay somewhere? Electrical problems always seem to stump me. I'd rather have a mechanical failure any day.

Thanks. KRW

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  #3  
Old 06-15-2008, 12:00 AM
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Thanks Craig. I also suspected the switch. I didn't know it had an electrical part seperate.
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  #4  
Old 06-15-2008, 01:43 PM
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Can anyone tell me if there is a DIY thread showing how to replace the electrical portion of the ignition switch? I searched several times but I come up with nothing.

How much of the dash has to come out? KRW
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  #5  
Old 06-16-2008, 06:28 PM
Craig
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You need to remove the ignition switch as a unit, then you can separate the electrical portion for the main unit. I don't know if there is a DIY; first you have to remove the tumbler using a paper clip to release the ring around the tumbler, allowing you to unscrew the ring. With the tumble removed, the switch assembly is removed from under the dash. It's not difficult, but it's very tight and having small hands helps. Plaan on spending half an hour upside down with your head under the dash.
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  #6  
Old 06-16-2008, 06:36 PM
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Quote:
Originally Posted by Craig View Post
You need to remove the ignition switch as a unit, then you can separate the electrical portion for the main unit. I don't know if there is a DIY; first you have to remove the tumbler using a paper clip to release the ring around the tumbler, allowing you to unscrew the ring. With the tumble removed, the switch assembly is removed from under the dash. It's not difficult, but it's very tight and having small hands helps. Plaan on spending half an hour upside down with your head under the dash.
I found that the smallest of the eye glasses screwdrives work best. No paperclip I found would fit.
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Old 06-16-2008, 06:48 PM
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Originally Posted by winmutt View Post
I found that the smallest of the eye glasses screwdrives work best. No paperclip I found would fit.
Mine worked with a fairly small paper clip that happened to be on my desk, but anything small and stiff enough should work too; a small screwdriver or allen wrench might be easier than a paperclip because it won't be as flimsy.
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Old 06-16-2008, 08:44 PM
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Thanks to both of you!

I've been wrestling with it for about an hour this evening. Thus far, I haven't gotten the paperclip to work. I'm going to try something stiffer. Does it matter which position the key is in? KRW
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  #9  
Old 06-16-2008, 08:48 PM
Craig
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Yes, the key needs to be in the #1 position so that the little hole lines up with the release mechanism on the tumbler. Try moving the key back and forth slightly around the #1 position.

Edit: If you lock at the photo, you can see the release that holds the ring in place:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ42E818NBW9&year=1983&make=MB&model=300-TDT-001&category=All&part=Ignition+Lock+Cylinder
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  #10  
Old 06-16-2008, 09:17 PM
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Although it shoud be simple, I'm having trouble. The paperclip will go into the small hole about a half an inch but no further. I've wiggled and tried everything I know to do. The key is in the #1 position and I can tell the clip goes a little further in there at this position.

I guess I will keep at it a while longer. I assume the key set will just pull straight out once I get the clip in far enough to trip the catch?
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  #11  
Old 06-16-2008, 09:29 PM
Craig
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Once you trip the catch, you will be able to unscrew the ring around the tumbler. When you feel the paperclip engage the catch, try turning the outer ring CCW. Keep the paperclip in place until the ring is removed.
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  #12  
Old 06-16-2008, 09:54 PM
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Finally!

I got the tumbler out. I wasn't turning the collar, I was trying to pull the key and switch staight out. It came out easily once I realized.

I loosened the squeeze collar that I thought was holding the switch mechanism in place. It will turn slightly, but it will not come out. Another catch somewhere? Or should I pry it off?

Thanks again for your help Craig. I would have still been at it next week sometime! KRW
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  #13  
Old 06-16-2008, 10:03 PM
Craig
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It takes a bit of wiggling to get the assembly out. Reach up and push the instrument cluster out of the dash to make more room (it should move about 2-inches without having to disconnect anything). With the clamp loose, move the assembly away from the steering column and up into the space where the instrument cluster was. There is barely enough room to get it free, but you shouldn't have to force it, much.

Edit: I believe there is also a button someplace on the assembly near the clamp that will free it up. I don't remember exactly, it's been a while.

I think that is the button you can see in the photo:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ42E81BDCQG&year=1983&make=MB&model=300-TDT-001&category=All&part=Ignition+Lock+Housing
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  #14  
Old 06-16-2008, 10:56 PM
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Those pictures are great. It helps to see it out of the car. I went ahead and took out the instrument cluster. Speedo cable, oil pressure line and a few electrical connections and it came right out. My plan was to try to fix the clock, but after looking it over, I might just skip that step and keep looking at my watch! I don't want to dig that deep into the Tach to get it out.

I'm sure I'll be able to get the lock assembly out tomorrow. I thought maybe there was a button because it moves a bit freely and seems as if it should come off easily, but it doesn't. The picture you posted gives the apprearance of one. I'll see.

The part I ordered (thanks for the link) should be in later in the week and I can get the car back on the road. My wife misses her car. She has been driving the Suburban. She much prefers the car. KRW
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  #15  
Old 06-16-2008, 11:16 PM
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Originally Posted by krwsenior View Post
I'm sure I'll be able to get the lock assembly out tomorrow. I thought maybe there was a button because it moves a bit freely and seems as if it should come off easily, but it doesn't. The picture you posted gives the apprearance of one. I'll see.
I'm pretty sure you need to push in the little button to free the assembly, but I've only done it once. As I recall, the "button" locks into a little hole on the sleeve that it fits into, someplace near that clamp.

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