Check code: Battery Voltage/DME Main Relay...HELP

[Mystikal]

My check engine light has been flashing randomly, and I just looked up the code using the table on http://www.unofficialbmw.com/repair_faqs/motronic.html. The Bentley swears my car has a 1.1, but the 1.3 method worked. :roll:

Anyways, it's telling me 1231, which is "Battery Voltage/DME Main Relay." This makes sense, as my lights are pulsing to no end and it's blowing through low beams in 10 minute intervals. Someone explain to me what needs fixing.

[Mystikal]

As the mind twirls, I'm thinking alternator. There is no other check code for it, and the problem is not enough voltage getting around the car. It's also still original at 264k kms.

[Charlie]

Voltage regulator.

You got a bosch or a valeo alternator? The VR is cheap, and usually the case as opposed to an alternator.

-Charlie

[Mystikal]

Thanks Charlie, as I read more into the Bentley and search on the net, I'm finding more and more fingers pointing at the regulator. There is a test to see if it's the alternator itself or the regulator, but you need another hand for throttle pushing. When my dad is free I'm going to get on it.

[Mystikal]

The voltage across the battery is way out of whack, it is definately the regulator. $13.82 at BMA for a Bosch, nice.

[Erick]

So I am definately stuck on the side of the road on a dead battery... CEL code 1231 flashing.

Any other causes than just the regulator? I'm not electrically inclined so can someone give me an idiots guide to e30 troubleshooting? :p

Oh and ps: battery/alternator light never came on

[jlevie]

Does the batter/alternator light com on when you switch the ignition on and go off when the engine starts? If not the bulb is bad and on early cars that will cause the alternator not to charge. If the battery goes dead while driving the car, the alternator isn't producing enough to keep the battery charged.

[Liam]

The diode bridge is bad in the alternator allowing AC current into your cars DC electrical system.

Replace the alternator also have your battery tested (a bad battery can toast an alternator).

[Erick]

Does the batter/alternator light com on when you switch the ignition on and go off when the engine starts? If not the bulb is bad and on early cars that will cause the alternator not to charge. If the battery goes dead while driving the car, the alternator isn't producing enough to keep the battery charged.

Light came on, yes.

Jonny Cash came to the rescue and we took a trip to the storage to pick up a spare alternator. We swapped the voltage regulators on the side of the road and less than 2 hours from my post I was back on the road.

Massive props to that guy for hooking it up.

- Erick

PS: In Liam's response.... it's a brand new Optima Red Top battery on the 318iS... about 1000 miles on it. So far it all seems fine. I cruised home on the highway in 4th gear to help charge the battery a bit quicker on higher revs. 75mph....4k rpms (4.10 LSD)........................25mpg! <3 M42.