e30 battery/alternator light
i have a 1988 325is and have been trying to troubleshoot my battery charging issue for months. the car died on me at a gas station randomly after a 30 mile drive. ive had the car for 3 years and have already noticed some "fixes" from the previous owner that i scratch my head about but previously to leaving me in need of a tow the car was running the best it ever has since ive got my hands on it. New plugs wires and cap, fresh oil n filter change, new air filter, MAF and ICV cleaned. first check when AAA came to the rescue was alternator output and voltage read 10.3 and dropping steadily so first thing i threw at it was new alternator. Upon replacement of the alternator i charged the battery to full 12.7v and fired it up only to find the alternator was not charging the batt just stayed at around 12v. read many posts about the ALT/Batt light on the dash and understood if it does not work the alt wont charge the batt so i went after that, replaced all new bulbs in dash and checked all fuses. Light still does not come on when key is turned to on, car still starts and runs great but only keeps 12v while running. now i started to check grounds all seem to be ok main engine strap, shock tower, valve cover, hood, and battery terminals are good and tight. Had battery cells checked at local parts store and everything seems ok. I'm stumped, any advice is greatly appreciated really want my car back on the road asap!
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You didn't mention it, so, how's your alternator ground cable? -
BMW fixed the battery light in the cluster issue with a resistor in parallel beginning in 1986 but yes it should come on with the key on prior to starting. In case you do have an early cluster in your 88, make sure the battery bulb is good and making good contact on the main board. Early clusters have 3 RED LED's on the service indicator instead of just 1 RED. The alternator on the M20B25 is solid mounted to the block without any rubber bushings to insulate it so there is no ground wire.
Actually, these days so many parts get switched around that we can no longer assume you have the correct engine, cluster, etc. Post some pics of the engine, alternator, cluster etc."I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj
85 323i M TECH 1 S52 - ALPINEWEISS/SCHWARZE
88 M3 - LACHSSILBER/SCHWARZE
89 M3 - ALPINEWEISS II/M TECH CLOTH-ALCANTARA
91 M TECHNIC CABRIO TURBO - MACAOBLAU/M TECH CLOTH-LEATHER
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Have you traced the wiring to make sure that the light is getting signal/power. There could be a break/splice in the wires that has now started causing issues. This is where i would start after doing what you have stated.
1989 325is l 1984 euro 320i l 1970 2002 Racecar
1991 318i 4dr slick top
Euro spec 320i/Alpina B6 3.5 project(the never ending saga)
Vintage race car revival (2002 content)
Mtech 2 turbo restoration
Brilliantrot slick top "build"Comment
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My bet is you have a bad new alternator out of the box... I would have it tested.Comment
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Also, check your grounds behind the kick panel.Comment
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Are u talking about the wire under the 13mm on the back of the alternator? Seemed fine but haven't put my meter on it beside when the car was on and got exactly the same reading at the batter 12.03v. The new alternator does seem to have a threaded post from the alternator body that my old one didn't I'd think it was for grounding but my old one alt body was not grounded.Originally posted by roguetoaster View PostComment
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This is my second one because I had that thought as well and had the first one tested, they said it was good but I asked for a new one anyways. Not sure what grounds under the kick panel I've heard of by the brake pedal but mine doesn't seem to have anything there.Originally posted by EyExR View PostComment
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Not sure how to check power behind the dash with it plugged in my harnesses seem very short barely enough room to get back there and unplug them to remove the cluster. Last night however I did realize the alt light does light up but very dim when the key is pushed slightly pass the on position but not all the way to the cranking the car to start position.Originally posted by ThatOneEuroE30 View Post
Thank you everybody for the help so far, much appreciated. I won't be able to dig into it tonight but I definitely will be getting into it tomorrow and this weekend.Comment
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Under instrument panel and above the brake pedal.Originally posted by Rs624 View Post
Not my pic but you can see the brown wires there:
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