Quote from Zoltan Nagy on December 14, 2023, 7:48 pm

I would like to share my experience regarding the LED replacement in the Zc31s instrument cluster. Unfortunately I forgot to take some snapshots of the steps, so for now you will need to follow my words, and come back some weeks later for the photos.
Before starting this work, I would suggest you to read and understand this guide for Zc32s, that is what started me on this adventure too. https://www.sssoc.co.uk/forum/topic/zc32s-instrument-cluster-disassembly-led-repair-guidance/
I will focus on the differences, and not detail all the steps.

The first part of the job is almost identical, disconnect the battery negative terminal first, then you need to remove the bottom- and top cover secured by plastic thingies. I found it helpful to turn the ignition switch to the on position for freeing the top part. You will see the instrument unit held by two more plastic clips at the top corners, and two PH2 head screw at the bottom corners. These are the only screws you will see at all. You will face the first important difference when you lift the unit. The connector on its back is a lever-style connector, this means you need to push the little flap behind the black lever, and lift the lever to release the connector. It doesn't need a lot of force if you hit the sweet spot.
Once you have the unit on your desk, you can start to open it up from behind, no need to remove the clear plexi from the front, only the black rear cover. Nothing else keeps the cluster in the case, so take care, and put it face up on the table.
Take the advice from Tom, and use some masking tape on the dial to mark the position of the hands, and try not to turn them at all. Removing the arms will not be easy, you will definitely need a metal pry tool to do it, and also some kind of soft cloth to push against, instead of the dial. The black caps on top of each arm are welded on the arms, and those welds WILL break. If you are very unlucky, I think you might need some CA glue to fix them back at the end, but I didn't. Pry them from both sides of the needle while supporting the other side with your finger until you hear the welds break (it needs a surprising amount of force). You can lift the arms once you got rid of the caps, again, pry tool and a good amount of brute force needed. You also have to remove the dial plate. There are cutouts on the fuel gauge and rpm gauge shaft. Lift the bottom part of the dial at the rpm gauge, push it a bit forward to release the plate from the slit on the shaft. Repeat at the fuel gauge. You need to rotate the plate about 45 degrees counter clockwise to match the cutouts at the speed gauge shaft and release it. You can now place the unit face down.
On the PCB side you will see 4 metal clips holding the screen (insteaf of the ribbon cable of ZC32s), release them first, then the 5 plastic clips at the edge, and you can now separate the PCB from the case.

!!TAKE CARE OF ESD PROTECTION AT LEAST FROM THIS POINT!!

You will see 2 types of LED-s. The "weird" ones light up the dials, if you need these, search for 4040 side LED, with forward voltage of 3-3.5V and 20mA current. The cathode (-) is on the right side. I suggest to change all the LEDs for one dial at least, (unless you want multi-color light) because it is close to impossible to match their luminousity and color. The others are 3528 size, with several different voltage and color for the telltale lamps, I don't really expect these to fail, so I didn't bother measuring their parameters, but since they are non diffuse LED-s, the color should pretty much decide the forward voltage, and you can trace back their resistor to find out their current. I can explain how to do it if needed.
After fixing the lights, putting it together is easypeasy. There are only a few things to take special care about:
- the metal bracket needs some fiddling to find its place.
- make sure to put the dial back to the slits at the rpm and fuel gauge before pushing down the bottom parts.
- make sure to put the needles to their original position
- MOST IMPORTANT: SUPPORT THE MECHATRONICS FROM THE BACK BEFORE PUSHING THE ARMS BACK TO THEIR PLACE!!

I hope this instruction will help you avoid some of the difficulties I faced with this fix.

Since I didn't have the exact LEDs needed for this panel, I will have to repeat this all over once I get the parts, and I will share the photos of the progress.