Aaron K limitedslip.net

19Mar/130

Jumpy gauges no more

Much like my e30 m30, the needles on the gauges jumped all around. When running, you could tap on the speedo and the rpms would jump up. The gas guage seemed to only show either full or empty. This is a typical problem with BMW guage clusters from this era. It is usually either a set of batteries leaking and corroding circuit boards, and/or cold solder joints. Kind of an annoyance, but the real bothersome piece was not knowing if the temperature guage could be trusted.

So I yanked the cluster out and completely disassembled it. The batteries were in decent shape, but they were replaced and relocated external to the cluster. Found a whole row of bad solder joints - check out the pictures below.

guage_cluster
Back side of the cluster. The illumination light bulbs (2 at the top) were pretty dim, so they were replaced with slightly brighter units (+2W approx).
Back side of the cluster. The illumination light bulbs (2 at the top) were pretty dim, so they were replaced with slightly brighter units (+2W approx).
Someone covered the service indicator lights with electrical tape.
Someone covered the service indicator lights with electrical tape.
Removed the electrical tape, but it'd been on there so long the residue remains.
Removed the electrical tape, but it'd been on there so long the residue remains.
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1
The new batteries and leads off the circuit board. The batteries didn't appear to be in series, so I ran leads for both.
The new batteries and leads off the circuit board. The batteries didn't appear to be in series, so I ran leads for both.
Unlikely need to change these often, but I did put in a disconnect for that purpose.
Unlikely need to change these often, but I did put in a disconnect for that purpose.
Closeup of the bad solder joints. All joints were reflowed on the board.
Closeup of the bad solder joints. All joints were reflowed on the board.
The service indicator board, if I'm not mistaken, and the batteries that are prone to leaking.
The service indicator board, if I'm not mistaken, and the batteries that are prone to leaking.
 


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