I have a 91 318i here (thread on it to come later) that has nonfunctioning SI LEDs. Everything else on the dash works with the exception of the SI LEDs, occasional speedo outage (tapping cluster does it), and econometer either only sweeps from 0 to 40 or sticks on 40. Tach, temp and fuel gauges fine. The car has had plenty of electrical issues so I'm not ready to blame these 100% on the SI board.
I pulled apart the cluster to replace all of the bulbs and clean it up. There was some mild corrosion on some of the speedo parts but otherwise it was clean. Traces had continuity but will reflow any way. Tested as many traces as I could on the main PCB and they all had continuity.
While in there I pulled the SI board and found the lithium batteries were dead. Otherwise the board looked perfect. No screw damage to PCB. I soldered in new 14250 batteries. Reinstalled the LED board and coding plug for testing.
When the gauge was reassembled for testing, still no SI LEDs. Every other gauge is the same as it was before.
I've checked all fuses and grounds. Not sure what else can be done other than to assume the LEDs or the LED driver on the SI board are toast.
I pulled apart the cluster to replace all of the bulbs and clean it up. There was some mild corrosion on some of the speedo parts but otherwise it was clean. Traces had continuity but will reflow any way. Tested as many traces as I could on the main PCB and they all had continuity.
While in there I pulled the SI board and found the lithium batteries were dead. Otherwise the board looked perfect. No screw damage to PCB. I soldered in new 14250 batteries. Reinstalled the LED board and coding plug for testing.
When the gauge was reassembled for testing, still no SI LEDs. Every other gauge is the same as it was before.
I've checked all fuses and grounds. Not sure what else can be done other than to assume the LEDs or the LED driver on the SI board are toast.