Seriously lost on this electrical issue. 87 300d

[jake12tech]

I made the dumbest mistake and I am here to admit it... I had the ignition on while working with the instrument cluster and the ground touched something and shorted something out. I went to go plug everything back in and it cooked up the instrument cluster.. The side where tbe oil pressure is, coolant and fuel is the side where it cooked. Smoke came out after 10 seconds of having the key on. It also blew out the fuse #9 for the interior lights..

I consulted the w124 zone manual and I'm still confused as to where to look and what to look at. The instrument cluster section isn't of much help on page 81.

I was wondering if theres a module that got damaged or I destroyed the whole harness.

I am very frustrated, electrical is not my strong suit...

[dieselbenz1]

Ugg not your lucky day Jake! Have you done a visual inspection of the harness and ground points yet? If it looks good maybe leave the cluster out and turn on the key. No more smoke and it should be localized within the cluster.

[jay_bob]

I looked at the diagram, the only thing that comes to the cluster involving fuse 9 is the flying lead to the clock. That one is very easy to get shorted out, the plastic insulator slides back easily and exposes the bare push on terminal. Fuse 9 is a constant hot.

Is the indexing pin missing on your cluster connector? If that pin is gone it is possible you plugged in the connector with the wrong clocking? That would cause all sorts of mayhem.

Hopefully on the harness circuits going to the cluster they coordinated the wire size vs. the fuse so that the fuse would blow before the wire got damaged.

My pin had broken off on the 87 so I had to create witness marks to know how to plug it back in. I ended up finding a good connector at the JY and replaced mine.

You may be able to figure out what happened if you can see which burnt traces lead to which pin on the circular connector and go backwards from there to see what circuit is involved.

I think I have a couple extra 124 clusters stashed away, let me know if you need another gauge section.

[jake12tech]

Guys thanks for the replies.. I don't see anything burnt or obvious in the connectors. Where else should I start looking? I tried another cluster yesterday and it started smoking. I have no clue now. Jay which connector are you talking about with the indexing mark. I don't see anything missing. I will likely need a cluster when I fix the problem. Not having a fuel gauge sucks.

[jay_bob]

In the center of the circle of pins on the plug should be a plastic post with a tab. This tab lines up with a hole in the center of the socket on the gauge board. The hole has a corresponding notch to accept the tab. This prevents the plug from being inserted incorrectly.

This post can break off when unplugging the cluster.

If the plug is inserted incorrectly, circuits will get crossed. I’m concerned you have damaged something on the vehicle side if you are smoking a new cluster assembly.

[jake12tech]

Originally Posted by jay_bob

In the center of the circle of pins on the plug should be a plastic post with a tab. This tab lines up with a hole in the center of the socket on the gauge board. The hole has a corresponding notch to accept the tab. This prevents the plug from being inserted incorrectly.

This post can break off when unplugging the cluster.

If the plug is inserted incorrectly, circuits will get crossed. I’m concerned you have damaged something on the vehicle side if you are smoking a new cluster assembly.

I'm afraid of the same thing Jay. I'm also not sure where to start. Amd I believe you're talking about that large circular round plug, the biggest one back there. I don't recall a tab so it must be broken. I'm considering sell the car at this point because the amount of frustration, and time removing the dashboard to access those harnesses.