Instrument cluster repair

[jht3]

i think i've diagnosed some faulty joints in my instrument cluster ('88 m3)

my left turn indicator doesn't light up (exterior lights work)
right illumination bulb doesn't light up (tach and engine temp)
obc illumination dies when i turn the headlights on

i've checked the bulbs, all are fine. i've also consulted the wiring diagrams and it can't be a wiring problem or fuse issue

so that leads me to believe i have some cracked solder joints or something on the circuit board. has anyone repaired their clusters in a similar fashion?

i'm going to "borrow" a friends cluster to see if the lights do work. then i'll go down the road of either resoldering the board, or cannibalizing his cluster to keep my odometer reading (his will be turned into a j-stock car so he doesn't need that crap thats broken on mine.

i haven't taken a cluster apart, so is it even possible to swap tachs or circuit boards? how difficult is it to reflow cold joints?

[James Crivellone]

All the parts from any 04/86 and up cluster will work (ones with the front coding plug)

Obviously you would have to swap gauge faces if your tach is bad, but that is far from difficult.

The only M3 Specific parts on teh cluster is the oil temp gauge (which is seperate from the tach and does not even connect to the internal PCB of the cluster), the M Bezel in the front, ,the rear casing (which has a cutout of the oil temp connector) and the Speedo, which is simply tuned a bit differently.

In terms of reflowing the joints, if you have another PCB available to you, then you can simply swap it.. reflowing joints is not that hard, and the solder joints on the board are fairly far apart so reflowing is simple.

[jht3]

so reflowing the board isn't to hard huh? good to know. i soldered on my playstation years ago and that was quite tough as the connectors were tiny and my soldering skill sucked. i've gotten better, so it shouldn't be too challenging

as for swapping parts, i may go that route. it sounds like i could just swap the whole PCB, or just the tach/odometer. i want to retain my 70k clock, not the 180k my buddy has in his m. i guess i'll find out what's in store when i connect up his entire cluster to test the wiring in my car and disassemble my cluster

god i hate electrical gremlins :twisted:

[jht3]

UPDATE

this past weekend down at VIR my previously non-working lights decided to work one morning. apparently it looks like the OBC lights are tied into the right side cluster light. later that night the lights didn't come on and haven't since. argh. banging at various parts of the dash didn't do the trick either

[Drew325is]

Dude...I just spent a weekend chasing faults in the cluster too. My left indicator light stopped working as yours did. What I found was a hair-line crack in one of the copper rails that leads to the indicator light on the main circuit board . The crack itself was located adjacent to the second screw hole to the left of the centre of the cluster. You'll probably notice the board is showing signs of stress around that area. I had to removed some of the coating off the rail to see the crack, and then solder it up. It might be worth invesitgating this kind of fault as the cause of your other problems. I noticed other parts of my board showing similar signs of stress as I already mentioned, so there could be cracks there too.

Also, my brake lining light had been playing up, but I found both solder joints at the end of a resistor had broken big time. Soldered them back, and all is sweet again!

A few other things that'll be useful to know is 1) get a multimeter, 2) try using wire to jump possible cracks to find their location, 3) becareful when re-flowing solder joints in crowded locations that you don't get soldr were it shouldn't be, 4) you can plug the main board into the car whilst it's apart to test a lot of repairs without going to the trouble of fully reassembling the cluster....in particular the dash illumination.

Hope this helps.