I have a 1985 300D turbo (California model) with a dead tach, an intermittent fuel gauge and a bouncy speedometer. The speedometer has been bouncy since I've had it, but the dead tach and funky fuel gauge are recent.

I pulled out the instrument cluster and, while there isn't much room to see anything without disconnecting everything, which I am loathe to do, I did notice a damaged wire (excuse the fuzzy picture please!)



If I'm not mistaken, the brown wire that seems damaged is a ground, which would explain the intermittent problems. This is on the plug that connects at the bottom left of the instrument panel, it's round and has a semi-circle shaped guide on the tip.

Is this the source of my problems, and anyone suggest the best way to fix it?

temp/fuel gages bounce, as speed increases

Try this

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Ok, I can try and run another ground wire to the panel, that sounds reasonable. Where do I attach it though?

My damaged ground wire goes into a plug, so to repair that directly I'd have to splice it. Can I just ground a point on the panel somewhere? Is there any particular spot?

There's a huge collection of grounds that are connected to the chassis. If you still have to original insulating material pull it away and you will see it.

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-Typos courtesy of my mobile phone.

I'm not worried about that end, I was planning on just grounding against the frame. I was wondering where on the instrument panel to attach it, since I can't connect it to the plug where the damaged wire is. Are there just screws on the back of the panel I can run off of?

attach the new ground to any one of the "screws" around back, that hold the three parts of the instrument panel together.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

It's not that hard to disconnect things and remove the cluster. Just disconnect the battery first. And put a golf tee in the oil pressure tube.

You only need the golf tee if you decide to turn on the engine... Ask me how I know this!

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Simon Shearer

1986 420SEL

2000 Porsche 911 Millenium Edition Carrera 4
2010 Lexus RX 350
2002 Kia Rio
2002 Hyundai Accent

I wouldn't trust a golf tee, get an old O/P gauge and thread that on if you have to start the car.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"