Repair a Blank Mitsubishi Colt Dashboard Display

The dash screen on a 2008 Mitsubishi Colt shows the clock, fuel consumption and other trip information, and after years in a hot dashboard it can go completely blank. The one I got from a friend had already been through a repair shop and still did not work. In this Instructable I show how I powered the display on the bench, found the chip pins that had lost their connection, and brought it back to life with a careful clean and fresh solder. The same approach works on a lot of other car electronics that fail from heat cycles, so here is what you will need to follow along.

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For the hardware, you need the faulty display unit itself and three DuPont jumper cables to connect it to power without the car.

For tools, I used a bench power supply that can do 12 volts with a current limit, a temperature controlled soldering iron with a fairly thick copper tip for the bracket and the smallest fine tip you have for the chip pins, a screwdriver for the two screws holding the boards together, and a microscope for inspecting the pins. A dental pick is very useful for scraping out resin and testing pins for movement.

For consumables, you need solder, flux, isopropyl alcohol and an old toothbrush for scrubbing the boards clean.

1. Bench Power Supply: https://s.click.aliexpress.com/e/_c3llIR8V
2. DuPont Cables: https://s.click.aliexpress.com/e/_c4PAsWh3
3. Soldering Iron: https://s.click.aliexpress.com/e/_c45sqC8p
4. Fine Soldering Iron Tip: https://s.click.aliexpress.com/e/_c4q7uWpb
5. Solder: https://s.click.aliexpress.com/e/_c3UGVo8Z
6. Flux: https://s.click.aliexpress.com/e/_c3rjyixr
7. Isopropyl Alcohol: https://s.click.aliexpress.com/e/_c3CFaoHT
8. Microscope: https://s.click.aliexpress.com/e/_c2JpVnat
9. Dental Pick: https://s.click.aliexpress.com/e/_c3R1uaUZ

The unit is made of two circuit boards. One carries the screen and the other is the main board, and each one has a main chip with many tiny legs soldered to pads on the board. From the factory, these chips are covered in a layer of resin.

A car dashboard heats up in the sun and cools down again every day, for years. Every time that happens, the resin expands and shrinks, and it slowly pulls up on the chip. Eventually some of the chip's legs crack free from their solder and stop making a connection. The chip then cannot talk to the rest of the circuit properly, and the display fails to start.

If the unit has been opened before, it is also worth looking for leftover resin and loose solder balls. A single small bead of solder sitting between two pins can create a short circuit.

Before opening anything, test the unit so you have a reference to compare against at the end. On this display, 12 volts goes to pins 7 and 8, which are the top two pins on the right side of the connector, and ground goes to pin 15, the second to last pin on the lower row. Check a wiring diagram for your exact model before connecting anything.

I joined two DuPont cables together for the positive side and used one for ground. Set the bench supply to 12 volts with a 1 amp limit and connect it. On my unit the current rose for a moment, then dropped, and the screen stayed empty. A working unit should at least show the clock, so this told me the display was trying to boot and then giving up.

The two boards are held together by a metal bracket soldered in two spots, plus two screws. Do not pull on the bracket, since the joints may already be cracked and you can damage the pads. Instead, put a thick tip on the soldering iron, set it hot (I used 410°C) and melt the solder until the bracket comes free.

Remove the two screws and gently pull the boards apart. They are joined by connectors at the ends, so they should separate cleanly and you can work on each one on its own.

Soak both boards in isopropyl alcohol and scrub them with a toothbrush for 5 to 10 minutes. Pay attention to the area around the chips. You are trying to remove old resin residue and any loose balls of solder that could be bridging pins.

Look closely as you go. On my boards I kept finding tiny solder beads spread all over, left behind by the earlier repair.

[Image: Resin flakes and solder balls removed from the board, collected on the bench]

Put the board under the microscope. Resin often stays stuck between the chip legs even after scrubbing. Use the tip of a dental pick to carefully scrape it out, working slowly so you do not bend any pins.

You do not need to get every last speck. Get it as clean as you reasonably can, since some of the leftover resin will soften and melt away once the soldering iron touches it.

With the pins visible, gently push on each one with the dental pick. A good joint moves together with its pad, so the pin barely moves at all. A broken joint lets the pin move on its own while the pad stays still.

Go all the way around the chip on both boards. I found three suspect pins on the screen board and one on the main board. Make a note of them so you can check them again after soldering.

Even if only a few pins are loose, go over all of them. If some joints have already cracked from heat cycles, the others are probably close behind.

Add a small amount of flux to the pads first so the solder flows well. Fit the smallest tip you have on the iron. If the solder will not melt properly, the tip is losing too much heat to the pad. I had to raise the temperature to about 450°C before it behaved.

Run the iron along each row of pins, adding a little fresh solder and melting each joint. Do not worry about bridges at this stage. When you are done, add a bit more flux and drag the iron over any bridged pins. The flux lets the extra solder pull onto the iron tip and the pins separate cleanly.

Repeat the process on the chip on the second board. It also helps to run the iron over the pins of the main connector and the connectors between the two boards.

Wash off the leftover flux with isopropyl alcohol and the toothbrush. Then go back under the microscope and push on every pin again with the pick. Nothing should move. The fresh solder should look bright and shiny, compared to the dull look the old joints had.

Another good check is to touch a pin with the soldering iron. If the heat transfers straight through into the pad and the joint, the pin is properly soldered.

[Image: Close up of the chip after resoldering, with shiny joints]

Line up the connectors and press the two boards back together. They only fit one way, so you cannot get them backwards. You can leave the bracket unsoldered for the test, since it only provides support.

Connect 12 volts to pins 7 and 8 and ground to pin 15, just like in the first test. If the repair worked, the clock appears on the screen and the backlight comes on. On mine, both came up straight away. Once you are happy with it, resolder the bracket and screw the boards together before the unit goes back into the car.

This display was brought back from completely blank to working again with nothing more than cleaning, flux and fresh solder. The real cause was chip pins that had cracked loose over years of heat cycles, made worse by resin and solder balls left behind by an earlier repair. The same inspection method of pushing on each pin and watching for movement under a microscope will help you track down faults in plenty of other car and consumer electronics.

The trickiest part for me was the microscope setup, so a better stand is on my list for a future build. For more repairs and electronics projects, follow along on the Taste The Code YouTube channel.