A friend of mine handed me the dash screen from a 2008 Mitsubishi Colt and asked if I could get it working again. This is the small unit that sits up in the dashboard and shows the clock, fuel consumption and a few other bits of information from the car. Right now it shows nothing at all.

I have worked on one of these units before for another friend, so I had a rough idea of where to look. Still, every repair has its own surprises, and this one had a few waiting for me.

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What I Found When I Opened It

The first thing I noticed was that this unit had already been to a repair shop. There were marks on the board that looked like corrosion, or something that had been smudged across it.

On these displays, the main chips normally sit under a layer of resin. You can still see it on some parts of the board. On the main chip, someone had cleaned most of that resin off, but not all of it. Little bits of it were still stuck on and around the chip.

That resin is actually part of the problem with these units. A car dashboard goes through a lot of heat cycles. It bakes in the sun and then cools down again, over and over, for years. As the resin expands and shrinks, it slowly pulls up on the chip, and some of the chip's legs end up losing their solder connection to the board. So my first suspect was the chip pins.

The unit is built from two boards. One holds the screen and has a similar chip with the same resin treatment, and the other is the main board. They connect to each other with connectors on the ends, and a metal bracket soldered in two spots holds everything together. One of those two solder joints was already broken, and the other one had a visible crack in it too.

Testing It on the Bench First

Since I did not have the car with me, I needed a way to power the display on my bench. I looked up some wiring diagrams and found that the unit needs 12 volts on pins 7 and 8, which are the top two pins on the right of the connector. Pin 15, which is the second to last pin on the lower row, needs to go to ground.

To connect everything, I used some DuPont cables. Two of them were wired together for the positive side and one went to the negative. I set my bench power supply to 12 volts with a 1 amp limit and connected it.

The current went up for a moment, so the unit was clearly drawing some power and trying to start. Then it dropped back down and the screen stayed completely empty. It looked like the display started to boot, found that something was wrong and shut itself off. I know that a working unit should at least show the clock when it gets power, so this gave me a clear starting point to compare against later.

Taking It Apart

To free the bracket, I used a fairly thick copper tip on my soldering iron at 410°C so I could get plenty of heat into those joints. I did not want to pull on anything with that cracked joint, so I let the heat do the work. The solder melted away quite easily, which makes me think it was a low melt solder.

There were also two screws holding the halves together. With those out, the two boards came apart and I could work on each one separately.

Right away I spotted a loose piece of solder on the screen board, sitting close to where the earlier repair work seemed to have been done. That was a good sign I was looking in the right place.

Cleaning Up the Mess

Step one was a proper clean. The board had tiny pieces of solder scattered everywhere. Just one of those little beads sitting between two pins could create a short circuit. I was not seeing a huge power draw, but you can never know which two pins might be bridged and how that could stop the whole thing from working.

I soaked both boards in isopropyl alcohol and scrubbed them with a toothbrush for a good 5 to 10 minutes. While doing that, I kept finding more of those small solder balls. I could pick one up on the tip of my finger and see another one sitting a bit further down. I have no idea how they all ended up there, but they were definitely not helping. Whoever opened this before me did not do a great job with the soldering or the cleanup.

After the scrub, the boards looked much nicer, but I could still see bits of resin stuck in between the chip pins.

Finding the Loose Pins Under the Microscope

Next I put the screen board under my microscope to get a close look at the chip. There was still quite a lot of resin between the pins, so I used a dental pick to scrape as much out as I could. Pieces were coming off, but it is slow work, and it is tricky to do while watching a monitor instead of your hands.

Once it was clean enough, I started gently pushing on each pin with the pick. On a good joint, the pin and pad move together as one piece. On a bad one, the pin moves on its own while the pad underneath stays still. That means the solder has cracked and the pin is no longer making a proper connection.

I found one of those near the end of the chip right away. Then I found a second one that moved separately from its pad, and a third looked just as suspect. I did not want to spend forever picking out every last bit of resin, so I got it as clean as I reasonably could and moved on. My hope was that any leftover resin would melt away once the soldering iron touched it.

I did the same cleaning on the chip on the main board. Most of those pins felt solid, but one of them moved without its pad when I touched it, so that board had a broken connection as well.

Resoldering the Chips

The Screen Board

Some of the pins looked fine, but I decided to go over every single pin anyway. When some joints have already cracked, the rest are probably not far behind.

I added a tiny bit of flux to the pads first. Flux cleans the metal surfaces and helps the solder flow where it should. Then I swapped to the smallest soldering iron tip I have, because these pins are really small.

My first try at adding solder did not go well. The tip was so small that even this little pad pulled the heat away and cooled it down. I raised the temperature to about 450°C and after that the solder behaved much better.

I went along each side of the chip melting every pin. I did not worry about bridges between pins at this point, because I planned to go back over them and clear them up afterward.

When I was done, I used more isopropyl alcohol and the toothbrush to wash off the leftover flux so I could see the result clearly. The pin that had been moving earlier was now solid. Every time I touched a pin with the iron, the heat went straight through to the pad, which tells me the solder is connecting everything properly.

The Main Board

Then I did the same on the main board chip. A little flux went on all the pins so the solder could flow easily, followed by fresh solder on every joint. This board rests on a metal pin, which made it harder to hold and film at the same time, so I worked in from one side and then from the other.

After that I poked at the pins again. They all felt solid, apart from one that still felt a little loose, so I gave it another pass. I did end up with a bridge between two pins at one point. The fix is simple: add a bit more flux and touch it with the iron. The flux lets the solder flow cleanly, the extra solder collects on the tip of the iron and the pins separate again.

The difference was easy to see. The old solder had a dull, tired look, most likely from all those hot and cold cycles in a car parked on a sunny driveway. The fresh solder was nice and shiny.

My microscope stand made this harder than it needed to be. I had to turn the microscope to the side to fit the whole board under it, so I think a custom stand with more range of motion would make a good future project.

Putting It Back Together

Before closing everything up, I also ran the soldering iron over all the pins on the main connector and on the connectors between the two halves. The two boards only fit together one way, so there is no risk of getting them backwards. You just need to line the connectors up and press them together.

I did not solder the bracket yet. It is only there for support, so the unit should work fine without it for a test.

Testing It Out

I connected the display to 12 volts again, and this time the clock came up on the screen. The backlight came on as well, even though it is hard to see on camera. That is the result I was hoping for, so I am calling this one fixed.

Conclusion

This repair was not as easy as it might sound. The hardest part was getting used to working under the microscope with such a tiny tip, and keeping my orientation right while using the pick on the board and looking up at a monitor at the same time. In the end, the problem came down to chip pins that had lost their connection over years of heat cycles, made worse by a messy earlier repair that left resin and solder balls all over the board.

If you have a car display or dashboard clock that has gone blank, cracked solder joints on the chip pins are a very good place to start looking. A careful clean, some flux and fresh solder can be enough to bring it back. This one is going back to my friend so it can go back in the car.

If you enjoyed following along with this repair, you can find more projects like it on my YouTube channel, and subscribing is the best way to catch the next one.

Tools And Materials

• Bench Power Supply: https://s.click.aliexpress.com/e/_c3llIR8V
• DuPont Cables: https://s.click.aliexpress.com/e/_c4PAsWh3
• Soldering Iron: https://s.click.aliexpress.com/e/_c45sqC8p
• Fine Soldering Iron Tip: https://s.click.aliexpress.com/e/_c4q7uWpb
• Solder: https://s.click.aliexpress.com/e/_c3UGVo8Z
• Flux: https://s.click.aliexpress.com/e/_c3rjyixr
• Isopropyl Alcohol: https://s.click.aliexpress.com/e/_c3CFaoHT
• Microscope: https://s.click.aliexpress.com/e/_c2JpVnat
• Dental Pick: https://s.click.aliexpress.com/e/_c3R1uaUZ