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hey guys,

Having a rough couple days with the E12. Seeing if anyone here could lead me in the right direction. I have a 1975 530i. Yesterday night while i was driving home my car randomly died on me. It would crank but would not turn over. I pushed the car off to the side and start to see if the fuel pump had took a dump on me. Luckly it still runs and sprays a good amount of fuel out. ( took off the cold start valve fuel hose and watched it spray fuel as i cranked it). Yes i know not exactly the smartest idea to spray fuel but i had a bottle on hand and pointed the fuel line into it. Next i checked spark. luckly my friend came, helped me cranked the car and found out that the primary coil wire was grounding onto the air box. Wrapped the wire up with electrical tape and PRESTO the car runs again!!! As I got into the car to drive home, I reved it a couple times just to make sure there was no abnormal missing and the car ran perfectly smooth. well.. up until i turn on my headlights and everything went dead in the car. And when i mean everything i mean EVERYTHING. Clock, hazard, headlight switch, ignition switch, everything wouldn't work. I jiggled around with the ignition switch and noticed that right before i get into position one i do get power back, but once i go passed it everything would die again. I went to check the fuse box and nothing was burned out. I also tried switching the low beam relay with the high beam relay to no avail. I next gave the fuse box a couple knocks on the side with my knuckles and power came back!! (weird right? O_o) so i thought, maybe there was a loose wire inside? Weird because last time my dad took it apart was back in the early 80s LOL. seems weird that problems would be happening now right? o wells. got back in the car, car starts right up, but again, once i pull the headlight switch to turn on the headlights it will kill everything. parking lights is fine. just when turning on the headlights itll kill everything. sometimes itll come back on its own. sometimes i have to wait. I drove the car back home with the lights off and the car ran perfectly fine. smooth all the way home. cept i couldnt see which it was dangerous. luckly the car died like 1 mile away so i just taped a flashlight to the hood and thought itll get me home. (such a top gear moment rite? lol).


anyways i checked inside the fuse box. all fuses are good and underneath there where no shorted wires. everything looks very clean inside. anyone have any ideas on where to look next?

I'd also look at the Voltage Regulator on the back of the alternator. It may be worn down to far.

Perhaps your ignition control module or main/fuel pump relay may be starting to fail if it's not the voltage regulator.

Eddie in TO wrote:I'd also look at the Voltage Regulator on the back of the alternator. It may be worn down to far.

Perhaps your ignition control module or main/fuel pump relay may be starting to fail if it's not the voltage regulator.

thank you for your reply eddie!

The voltage regulator on the car is actually an external regulator. I recently have changed the brushes not too long ago but seeing how the alternator light would not turn on once the car was running, that means the alternator is charging correct?

Curious as to where i should locate the ignition control module for the car? Also not sure where the fuel pump relay is located at. The fuse box only has 4 relays in it. one high beam, one low beam, one horn, and other is relief relay (or something along that line. i know it doesnt say fuel pump relay).

Yes your right, the alternator light would not be lit if it's being charged correctly.

The ignition control module may be mounted on the RH side beside the windshield washer bottle.
I say 'may' because this is where it's located on an '80 model but I can't imagine BMW relocating these very far from these locations during the E12 life span.

On a 1980 528i, the fuel pump relay is combined with the main relay which is mounted off the LH strut tower directly behind the coolant expansion tank. It's the black box with a mounting tab on the top center shown in this image.


Sadly, I'm not familiar with electrical gremlins in these cars but hope the above may be of some assistance.

Everything died when you turned on the headlights and stayed that way when you turned them off? That's easy, it's the connections at the battery. Remove, clean both sides and both terminals, and reinstall. I don't care if they look ok, do it. Get it down to shinny metal. That'll fix it.

Eddie in TO wrote:Yes your right, the alternator light would not be lit if it's being charged correctly.

The ignition control module may be mounted on the RH side beside the windshield washer bottle.
I say 'may' because this is where it's located on an '80 model but I can't imagine BMW relocating these very far from these locations during the E12 life span.

On a 1980 528i, the fuel pump relay is combined with the main relay which is mounted off the LH strut tower directly behind the coolant expansion tank. It's the black box with a mounting tab on the top center shown in this image.


Sadly, I'm not familiar with electrical gremlins in these cars but hope the above may be of some assistance.

thank you very much i would defiantly take a look at that.

Mike W. wrote:Everything died when you turned on the headlights and stayed that way when you turned them off? That's easy, it's the connections at the battery. Remove, clean both sides and both terminals, and reinstall. I don't care if they look ok, do it. Get it down to shinny metal. That'll fix it.

Hello Mike,

Believe it or not that was actually the first thing i did when i tried to diagnose the problem. I remember reading up on no start issues before and I remember you saying that and hence that was the first thing I did. unfortunately it didn't solve the problem.


I do have a theory though, Since the it only kills the engine when the headlights are turned on, would it be because the headlight switch and or the ignition switch is going bad? Could it be possible that either one would cause a short? Reason why i say that is because since the car is ok when i have pulled the headlight switch all the way when the ignition key is off. but once i put the ignition switch to position two, everything would cut out. Maybe ignition switch is going bad?

I also think that the problem is not related to voltage regulator, alternator, etc, since you write you observe faulty behavior also with the engine stopped.

I would start by cleaning the contacts in the fuse box by removing all the fuses, relays, and clean them with some contact cleaner or even WD40. Check if the fuses are clean and of correct value. If relays are identical between them, try to swap them, maybe one of them is faulty. My high-beam relay went bad one day, turning on high beam on acceleration , so they do break.

Also, if you are handy, check out the electrical schematics of the car and try to understand the relation between headlights and ignition switch power supply.

The main consideration is based upon you've said:
"Everything died when turning the headlights on and came back, when turning them off"
1. You have "bad connection" problem.
2. As I understand, when you turn only the ignition switch, without the headlights - the starter turns vigorously and engine starts - so the connections at the battery are OK. The engine ground cable is OK, the starter cable is OK. So, everything with the ignition, voltage regulator, the double relay, the fuel pump, the ECU and etc. is OK.
The problem appears, when the headlights are ON - so, you have to find the bad connection (ground or live 12V) which is common and joint to the both - the beams and the dashboard for example. The lights in the dashboard and powering the ECU, ignition and the pump have lower consumption compared to the headlights. Because of the bad connection and great current losses at that point - the voltage dropped under the working limit.
Maybe this point is in the fusebox - everything seems OK, but the contact is bad. I think - you haven't short anything, because all fuses are OK.
The headlights switches are only switching the relays in the fusebox - the real current is there. Finally - check the ground and live 12V connections around and in the fusebox. Make some voltage measurements with a voltmeter in both cases (with and w/o the headlights) - it is convenient to measure on the both sides of the fuse holders (these fuse holders are bad link also). In this way you can meassure the voltage drop and make a research, moving through the cables toward the battery - I believe then you'll find the bad connection.

Good post, Alexander

Thank you Bart (Falkenberg). I see - we wrote our posts almost at the same time...
You were a bit faster than me, but the main idea is similar (Mike was the fastest... ).

DEMIURGE wrote:The main consideration is based upon you've said:
"Everything died when turning the headlights on and came back, when turning them off"
1. You have "bad connection" problem.
2. As I understand, when you turn only the ignition switch, without the headlights - the starter turns vigorously and engine starts - so the connections at the battery are OK. The engine ground cable is OK, the starter cable is OK. So, everything with the ignition, voltage regulator, the double relay, the fuel pump, the ECU and etc. is OK.
The problem appears, when the headlights are ON - so, you have to find the bad connection (ground or live 12V) which is common and joint to the both - the beams and the dashboard for example. The lights in the dashboard and powering the ECU, ignition and the pump have lower consumption compared to the headlights. Because of the bad connection and great current losses at that point - the voltage dropped under the working limit.
Maybe this point is in the fusebox - everything seems OK, but the contact is bad. I think - you haven't short anything, because all fuses are OK.
The headlights switches are only switching the relays in the fusebox - the real current is there. Finally - check the ground and live 12V connections around and in the fusebox. Make some voltage measurements with a voltmeter in both cases (with and w/o the headlights) - it is convenient to measure on the both sides of the fuse holders (these fuse holders are bad link also). In this way you can meassure the voltage drop and make a research, moving through the cables toward the battery - I believe then you'll find the bad connection.

thank you for the post! i would defiantly check everything out with a voltmeter to find any inconsistency.

one thing i mentioned was that the power doesn't instantly come back on with headlights turned back off. Sometimes it takes couple mins before power comes back. Seeing how its not instant and also not consistent, would there be something else that could be causing the problem?

I remember you've said:
"I next gave the fuse box a couple knocks on the side with my knuckles and power came back!!"
This is another reason to check the fuse box, the fuses and the springs of the fuse holders. Examine the cables and connections underneath also.
And yes - it is strange, that the power returns, but not instantly and it is possible if we presume that this is a simple coincidence.
I believe - the power return is sudden, possibly a bit sparky (because of a bad contact), but not gradual and flowing... - that would be a really strange issue (speaking "electronic" - like charging a big capacitor with limited current or recovery of a shorten or overload battery).