DIY Cluster Repair: Odometer Reset Switch Failure

[dschneider]

I'd been having trouble with my odometer/trip reset button for a few years. It started getting flaky: requiring multiple, forceful presses in order to use. I put up with it, but two months ago it finally gave up the ghost. I found my battery almost drained and the odometer permanently illuminated, with the trip counter set to 0 and not updating while I drove.

A little searching surfaces a few threads here and on M5 board with owners reporting similar troubles: difficulty or inability to reset trip or cycle check control/OBC display, odometer permanently illuminated. The most useful thread was on M5Board, including some pictures showing the corrosion: https://www.m5board.com/threads/odom.../#post-2250645

Time to crack open the cluster and make the repair. Here's the procedure, with more-complete photographic steps:

1. Remove the cluster. There is a plastic flange at the top of the cluster acrylic with two small philips head screws into the dash. This is the entire cluster retention mechanism.

Attachment 702218

The cluster tilts and pulls forward. You may be able to sneak it out from behind your wheel, especially if you have a telescoping wheel. However, if you have a fixed wheel you will have to drop the steering wheel. Remove the wood trims on the knee panel to access the retaining screws: the right side just lifts out, the left side lifts on the left edge and then slides left to release a spring clip. These trims are held in place by threaded studs that push into metal-edged retaining clips. It's possible that you will break the clips, I did the first time I had these apart. Minimum order quantity on the clips was like 10, so I have extras if you break yours and need a replacement. PM me.

Remove the screws at the top edge, two under the radio trim (the vertical black plastic trim piece just lifts away/off, it has a good clip design that it unlikely to break), two or three along the bottom edge of the panel, and single screw on the left/door side under the door vent pass-through. They're assorted sizes, so keep track of them. Mine were definitely scrambled by a previous monkey before I got the car, so I've had to do a best guess for which ones go where.

Now you can remove the knee crash pad. You can access the two steering column bolts without doing this, but it's a tight fit and they're impossible to get back in. These two bolts are large self-tapping units, with a tapered end that is very difficult to align. So do yourself a favor and remove the knee crash pad now. Its retention screws will be obvious.

Now you can remove the two steering column retention bolts and press the wheel down and away to access the back side of the cluster. There are four connectors, remove them by lifting on the black retention levers.

2. Open the cluster. There are two black knobs on either side, with labeled arrows indicating direction to open and close. They're half turn latches. The cluster is a clamshell design, and the main board is attached to the back shell. There are two extremely fragile hinges at the top of the cluster. There's also a paper seal, which may have already fallen off.


There's at least 50-50 odds that you break one or more of the hinge clips if you try to separate the cluster shells. Opening the back panel should be safe if you're very gentle. If your car has lived outside and/or in a hot climate, the heat of the sun on the dash makes the plastic extremely brittle. I managed not to break the clips on my first cluster, but did on a second spare one that I opened for comparison purposes. Even re-gluing them didn't work: superglue holds really well, but the plastic next to it broke in the same way. I did that three times before giving up on that cluster. The problem appears to be a slight wide spot caused by the injection moulding seam, so my next attempt will involve smoothing that and narrowing the hinge "pin" with sandpaper.

You may wish to apply a little lubricant to the hinges before opening. The display board and main board are connected by very large conductive studs in clamp contacts, and there's another board-edge type connector in the middle. Gentle but firmly lift the cluster back housing from the bottom to separate.

3. Assess corrosion. Here's an image of the inside of the clamshell, showing the main board. The OBC/check control and trip reset switches are circled in red.

Attachment 702220

Here's a closeup of one of the switches. Note the white buildup: this is some sort of oxidation, and the cause of our problems.

Attachment 702219

The oxidation appears to start inside the switch, interfering with the switch function, but can expand outside the switch housing. The ultimate "problem" is caused by conductive oxidation bridging the switch contacts.

Attachment 702221

Here's the backside of the switch. Note that the corrosion is creeping out.

--- snip for photo limit ---

[dschneider]

4. (Optional) Remove the main board from the clamshell. You can get inside the switches from the exposed side to clean them, but additional corrosion can be found outside of the switches. I removed the main board to make an assessment, and to de-solder the switches in order to clean them completely.

Attachment 702229

The board is retained by ten (10) heat- or sonic-peened alignment studs. In order to remove the board, I used a dirty old cone-shaped soldering iron tip to gentle heat the plastic. While pulling up on the board, the plastic re-formed to fit through the stud hole. You could also simply drill the tops off carefully. In order to reattach the board, I used a bunch of small bolts with nylon washers, but you could re-peen the plastic (this might be fragile, not recommended) or just dab a drop of hot glue into each hole. The holes in the plastic alignment posts are almost perfectly sized for M3x0.5. I got a tiny tap and a set of 12mm long bolts with nylon washers to retain. For extra certainty, I also dropped a dab of superglue onto the threads from the back side of the hole during reassembly.

5. (Optional) De-solder the switch housing to clean it.

After seeing the amount of corrosion present, I decided to de-solder the switches entirely to clean them. I wanted to be certain to eliminate any corrosion between the contacts that might be hiding under/behind the switch housing. This was a good excuse for an upgrade, so I bought a new HAKKO digital soldering station.

I carefully heated the legs and de-soldered the switch from the back. Here's what the switch looks like when disassembled:

Attachment 702231

6. Clean the switch thoroughly. I used De-Ox-Ide, but another similar antioxidant switch/contact cleaner would work. That wasn't entirely adequate in my case, so I disassembled the switch and soaked all components in rubbing alcohol and scrubbed gently with a toothbrush until all residue was removed. I then rinsed and reassembled. Picture shows two switches disassembled.

Attachment 702230

The switch is composed of four pieces (excluding the contactor): 1) injection moulded plastic body, consisting of a guide tube for the contactor arm and a base containing the contacts, 2) 2x stamped and bent metal contacts, with legs to through-mount on the PCB and a contact bridge surface, 3) a back/insert that barely clips into the main body to hold the contacts in place, also featuring two alignment studs.

Attachment 702234

The retention insert has two tiny snap catches on the sides, and simply pulls out from the main body. Be gentle and don't break the alignment pins. We'll use a little glue during reassembly to be sure it stays together.

Attachment 702235

Nice and clean!

[dschneider]

7. Clean the board thoroughly. As you can see, there was corrosion present under and behind the switch body that I couldn't access. Again I used rubbing alcohol and a toothbrush, and tried thoroughly with compressed air.

Attachment 702236

Also clean the contactors. There are plastic rods sticking through from the front housing of the cluster, and the contactor that bridges the switch is actually a conductive rubber donut. It slides off the stem and is retained by a little bump, so you can remove to clean it thoroughly.

Attachment 702237Attachment 702238

8. Re-solder switches, if applicable. This is simple through-hole soldering. Don't toast the PCB and you should be alright.

9. (Optional) Apply conformal coating to back side of switches. You can use acrylic clear nail polish. This will help prevent moisture-accelerated corrosion from occurring in the same way.

10. Re-assemble main board into housing, if applicable. As noted before, I used M3 12mm bolts with nylon washers to screw directly into the hollow alignment studs. Originally sonic or heat-peened, mine were damaged too much during disassembly, I didn't trust them to hold the board in place. I also didn't want to use hot glue, although that would be a totally suitable solution as well. You'll need 10x of them, and to clean up the stud tops to pass through the board easily.

11. Replace any dead cluster bulbs while you're in there, then close the clamshell. Reassemble everything into the car in the reverse of disassembly. Note that the bolts holding the steering column bracket are very difficult to re-thread if misaligned, and since they're self-tapping with an aggressive taper they're easy to cross-thread. Be careful not to cross thread them.

I am happy to answer clarifying questions, and have a spare cluster disassembled on my bench right now if you want additional pictures of any component.