Thought I'd post this here for anyone with similar issues. My 87 235es came with some wiring/electrical problems. The PO had put a stereo in and it wouldn't turn on, also the cluster tach and econometer were acting erratic. I changed the Cluster SI Board and sorted out the tach issue but I was getting a weird Voltage at the radio, 10.5-11V when the Battery was 12.5. This was causing the radio to not power on. Power at the fuse box was 12.5V both sides of the fuse so I figured the problem had to be in the harness somewhere.
I Looked up the wiring in the ETM and there are several splices in the harness where it runs down the Drivers kick panel and along the rockers, one of which is where everything is spliced for the Red/Grn fuse 21. This includes parts of circuits for the Radio, Econometer, Check Panel, Interior Lights, ECU, Tach, etc. I had to unwrap the harness along the rocker and found that these splices are only crimps wrapped in friction tape, and not water tight...
I worked my way back towards the kick panel and found about 7 splices including the fuse 21 one, all of them were corroded to some extent, some worse than others. Fuse 21 was totally rotten, and all the wires totally fell apart when I unwrapped the tape. Note all the Green Copper Oxide, formerly wire strands.
I guess over the years water from leaks into the car and junk from peoples feet soak into the harness through the carpet and eat the splices. If your car is acting weird electrically, and you have wet carpets from time to time or a lot of water in your footwells, I suggest checking these splices for corrosion. I redid all the splices and put glue heat shrink over them, should last the life of the car!
Once I fixed them all the voltages were back to normal, radio turns on! I'm not sure what else wasn't working right, just got the car, but the car is running a lot better too so maybe there were other systems not getting the correct voltage.
I Looked up the wiring in the ETM and there are several splices in the harness where it runs down the Drivers kick panel and along the rockers, one of which is where everything is spliced for the Red/Grn fuse 21. This includes parts of circuits for the Radio, Econometer, Check Panel, Interior Lights, ECU, Tach, etc. I had to unwrap the harness along the rocker and found that these splices are only crimps wrapped in friction tape, and not water tight...
I worked my way back towards the kick panel and found about 7 splices including the fuse 21 one, all of them were corroded to some extent, some worse than others. Fuse 21 was totally rotten, and all the wires totally fell apart when I unwrapped the tape. Note all the Green Copper Oxide, formerly wire strands.
I guess over the years water from leaks into the car and junk from peoples feet soak into the harness through the carpet and eat the splices. If your car is acting weird electrically, and you have wet carpets from time to time or a lot of water in your footwells, I suggest checking these splices for corrosion. I redid all the splices and put glue heat shrink over them, should last the life of the car!
Once I fixed them all the voltages were back to normal, radio turns on! I'm not sure what else wasn't working right, just got the car, but the car is running a lot better too so maybe there were other systems not getting the correct voltage.
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