When I bought this car the PO said it wasn't charging or had a drain and needed an alternator. The alt bracket was loose and belt was slipping a bit so I thought that was the culprit. I bought a new battery since the old one was trashed. I had driven it around but only a few miles and everything seemed okay except the battery was low.
When I test drove the car the other day, I noticed the speedo didn't work and the battery light is out so I pulled it and went thru all the traces. Then I remembered...on early models, pre 86, the alternator cannot charge the battery if the cluster battery bulb is out. Turns out the bulb was good but the socket wasn't making good enough contact and actually measured open on the DMM. I reflowed all the joints on the PCB and as well as the solder contacts for the battery bulb this time. Now the battery light illuminates with the key on as it should. I can't drive the car since the front end is in pieces but I'm confident I fixed both the speedo and the charging issue. The ETM shows power that goes through the battery bulb also goes through the speedo. BMW later updated clusters with a resistor in parallel to prevent this problem.
Now that the boring stuff is out of the way...I wired up the 10" JL Sub and Fosgate amp that came with the car. I like sealed enclosures as the bass is tighter and they can be smaller size so you still have plenty of space.
Also forgot to mention, I installed a 2nd trunk light as well. This combined with the light from the parking lights really lights up the trunk at night. Excellent low cost mod.
When I test drove the car the other day, I noticed the speedo didn't work and the battery light is out so I pulled it and went thru all the traces. Then I remembered...on early models, pre 86, the alternator cannot charge the battery if the cluster battery bulb is out. Turns out the bulb was good but the socket wasn't making good enough contact and actually measured open on the DMM. I reflowed all the joints on the PCB and as well as the solder contacts for the battery bulb this time. Now the battery light illuminates with the key on as it should. I can't drive the car since the front end is in pieces but I'm confident I fixed both the speedo and the charging issue. The ETM shows power that goes through the battery bulb also goes through the speedo. BMW later updated clusters with a resistor in parallel to prevent this problem.
Now that the boring stuff is out of the way...I wired up the 10" JL Sub and Fosgate amp that came with the car. I like sealed enclosures as the bass is tighter and they can be smaller size so you still have plenty of space.

Also forgot to mention, I installed a 2nd trunk light as well. This combined with the light from the parking lights really lights up the trunk at night. Excellent low cost mod.
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