Electrical problems in my 3.0CS

[Drew Gregg]

During the first week of November, I drove 500 miles to Hilton Head/LOTA East/Octoberfest. The car ran fine until I had a voltage surge that had numerous things all happen at once to the electrical system. The wipers started going 100 MPH without being turned on. The tach bounced all over the place. The car backfired and then went dead on the side of a 2 lane road. The car was towed to a BMW/Mercedes shop owned by a guy who has worked on these cars for over 25 years. He found the 12 month old red-top AGM Optima battery had an internal failure that caused the voltage surge. He replaced it with a World brand AGM battery he uses in small airplanes. The car started right up and I drove it for several days in the pouring rain and then 500 miles back home. The surge blew out my fog light switch indicator bulb and both 20 watt city lights I use as daytime running lights in my Hella headlights with H4 bulbs. I also lost my quartz restored clock.

I knew I had to check the alternator and voltage regulator. The Bosche alternator is putting out 14 volts at the terminals. My voltage regulator was giving me 12-17 volts at the trunk-mounted battery and I suspect that is what caused the Omni battery to fail.The mechanic back in South Carolina told me the Optima battery is designed for modern cars with 95 amp output and is not a good application for our 45 amp alternators. I bought a new voltage regulator and a plug-in voltmeter-Equus3721 diagnostic tool. This $20 device plugs into your cigar lighter and gives you real time voltage and charging status while driving. I bought it on EBay and now know the charging system is working correctly.

About 3 weeks ago,I start up the car and turn on the headlights. The instrument lights are on until I slam the door shut. The instrument lights go out and #2 fuse is blown. The label says #2 fuse is only for the license plate and instrument lights. I then disconnect the license lights after inspecting the wires for a short. Now that there is no load on the license lights/wiring, the new fuse blows out the instant the light switch is turned on. That means the short is somewhere in the dash.
Has anyone had a similar problem and can tell me where to look for a short?

Today I started the car and turned on the headlights. My H4 bulb on low beam on the passenger side is now a dull yellow. I pulled the headlight and measured only 4.5 volts in the terminal.
Has anyone had this electrical problem? Please note this is a USA car that had the traditional sealed beam headlights and the H4 Hella's have been working for over a year w/o problems.

The first pic is the new Behru regulator. The 2nd pic is the 20 watt halogen "city lights" that were custom wired to be used as daytime running lights operated by the green fog light switch under the steering wheel. The headlight buckets had to be cut to allow the extra city light to fit into the bucket.

 

[Stevehose]

sounds like you need an exorcist

 

[rsporsche]

1st question - have you put a relay on your low beams?
2nd question - have you considered rewiring your headlights directly to the battery and use the existing wiring just to turn the lights on / off? right now, all of the voltage runs through the headlight switch to power the lights.

i would check the headlight switch and the wires around it for an issue. remember the license plate lights are powered by the headlight switch.

 

[Drew Gregg]

1st question - have you put a fuse on your low beams?
2nd question - have you considered rewiring your headlights directly to the battery and use the existing wiring just to turn the lights on / off? right now, all of the voltage runs through the headlight switch to power the lights.

i would check the headlight switch and the wires around it for an issue. remember the license plate lights are powered by the headlight switch.

Scott- good Ideas. I had used relays on my Marchal Ampilux headlights in the 2002. Getting wires to the battery in the trunk will be a project. Thanks for the suggestions.--Drew

 

[Arde]

Strange things can be caused by problems on the 12V path of a given circuit, or the ground path.

If the problems started with the overvoltage condition, I do not think that can trigger ground path problems, I think it would be 12V issues. I had intermittently blown fuses due to a loose unused wire that moved around when driving at speed...
In your case it could be an insulation that got melted during the initial overvoltage.

There could be active components that were damaged in the event and now misbehave. The solid state blinker? Some relay? Carbon deposits in switches like the headlight switch that, as mentioned, carries the full load for low lights?

The root cause process probably requires isolating circuits, then isolating components, and possibly running without the alternator wired so it operates just on the battery without voltage rectification and regulation at work.

 

[adawil2002]

I had a similar problem with fuses blowing after I hit a big bump in the road. Kept blowing fuse 2. Took me close to a week to track the problem down to a loose City Light holder on the driver side was grounding & blowing the fuse when I turned the lights on.

@Arde has good advice.

 

[Ohmess]

Strange things can be caused by problems on the 12V path of a given circuit, or the ground path.

If the problems started with the overvoltage condition, I do not think that can trigger ground path problems, I think it would be 12V issues. I had intermittently blown fuses due to a loose unused wire that moved around when driving at speed...
In your case it could be an insulation that got melted during the initial overvoltage.

There could be active components that were damaged in the event and now misbehave. The solid state blinker? Some relay? Carbon deposits in switches like the headlight switch that, as mentioned, carries the full load for low lights?

The root cause process probably requires isolating circuits, then isolating components, and possibly running without the alternator wired so it operates just on the battery without voltage rectification and regulation at work.

Good advice here. I agree that the problem is more likely on the 12v side, which means isolate and go through circuit by circuit.

I'm probably going to sound like a broken record here, but this is massively frustrating if you don't take it into account. I wasted hours and hours on this. Recall that our cars have power distribution built into the fuse blocks. On earlier model cars, fuses 4 and 5 distribute unswitched power, while fuses 6 & 7 distribute switched power. When testing upstream of these fuses, you need to test all of the upstream circuits as a single unit because they are connected at the back of the fuse block.

Another comment based on the massive amounts of time I spent chasing burnt wiring in my car: check the continuity on the wire from the alternator to the back of the idiot light in the dash. This wire not only causes the dash light to light up when the alternator is not fully charging the battery, it is the signal to the voltage regulator to send more voltage into the system. When the battery is supplying voltage to the vehicle, this light is illuminated by the difference between the battery voltage and the alternator output voltage. This is why the light illuminates when our cars are started until the engine spins and the voltage output from the alternator equalizes the circuit. Once that happens the light goes out. Similarly, when the alternator falters and is not putting out sufficient voltage, the voltage draw from the battery illuminates the dash light in proportion to the draw. If the alternator fails slowly, the light is faint. As the alternator gets worse, the light gets brighter as more of the car's voltage comes from the battery. And if there is no alternator output, such as when your fan belt breaks, the light shines brightly.

Someone had done a poorly soldered splice in my car into that wire. The splice was decaying over time which increased the resistance of the wire. That increased resistance meant that the signal to the voltage regulator was actually less than the voltage being used by the car. So the voltage regulator did its job and increased the alternator output to match the voltage it was seeing. Output went over 19v before I found the problem. I replaced the entire wire.

 

[Arde]

...

Another comment based on the massive amounts of time I spent chasing burnt wiring in my car: check the continuity on the wire from the alternator to the back of the idiot light in the dash. This wire not only causes the dash light to light up when the alternator is not fully charging the battery, it is the signal to the voltage regulator to send more voltage into the system..

Agreed. Here is a writeup I did for a guy chasing these problems on a Fulvia and they liked it. Credits to SFDon for content.

In general the alternator rotor is excited by the current going from the battery through the charge bulb in the dash just to get some magnetic field before the alternator is producing any. The rotor is also excited by the output of the alternator itself so once it starts it self-sustains without pushing too much current through the bulb.

When the alternator voltage is above the battery voltage both sides of the bulb are at equal voltage because all involved diodes are conducting. The light should be OFF. If the light is OFF all the time it may be that the bulb is burned or that the rotor coil is open. The bulb wire by convention should be the only BLUE wire in the engine bay, so one can disconnect the blue wire (on the side that is not the alternator) and connect it to the battery. The alternator rotor is now excited even with a burned bulb and one can drive the car. If the rotor coil is open this will not help. An open rotor can be diagnosed by grounding the alternator side of the blue wire by observing the bulb does come on.

The voltage regulator is always a suspect when things do not work right, that is because it can interrupt the rotor current on its own, that is how it regulates (by modulating the average rotor current). I think one can briefly bypass the voltage regulator at low revs to diagnose things, namely to confirm a new one is needed.

I disagree with the notion that the battery provides the current in steady state to avoid the alternator being a mechanical load on the engine. I think the battery is used just for starting the engine and from then on it is the alternator providing the current, but maybe there are some subtleties there I miss.

My (Fulvia) alternator bulb does flicker at idle and I read that is pretty normal. That means that the regulated alternator voltage oscillates between being slightly below the battery voltage to slightly above at idle speeds.

Now, a bulb that stays on solid while the engine is running could be explained if some of the diodes are shot open (as in not conducting). I guess a bad VR could also cause that if it operated erratically (sometimes charging the battery and sometimes regulating well below).

 

[Ohmess]

Yes. Arde raises another point to be diagnosed. Check to see that the idiot light bulb is intact. Because of the voltage regulation element of this circuit, a burnt out bulb can cause voltage regulation problems.

 

[Drew Gregg]

My electrical problems were solved this morning by David Masi. Dave worked for The Werke Shop in Illinois for several years taking apart and assembling the coupes brought into their shop for repairs and restorations. He has his own business now in the South Florida area working on classic Bimmers. He has fixed several items on my car that were botched by the restoration shop that had the car for almost 2 years. I had removed all of the trunk elephant skin to inspect the wiring and removed the lamps that were not working to try to isolate the short. It looked like the problem was in the headlight switch and I knew he would have the tool to correctly remove the switch from the dash.
Dave took everything apart including the pin block that plugs into the switch terminals. He used special BMW branded tools to remove the terminals. Then he powered up each circuit behind the fuse block. All of the lights that were off went on independent of the headlight switch. Then the switch was tested and blown clean. There must have been some dirt inside the switch that caused the short/blown fuse #2.
After all was put together,I stood behind the car while he put on all of the lights and blinkers. All worked. Then he put the car in reverse and asked if the 2 clear lights came on. And they didn't. What??? They worked back when I first got the car. He crawled under the car and found the wires were missing at the transmission terminals. Then he found the wire wedged next to the coolant expansion tank. The wires were connected and the reverse lights now work. This is another example of a shop that brags about their million-dollar award-winning restorations that knows nothing about BMW CS.
BTW--The passenger H4 headlight now works at full voltage.
Thanks to Chris, Arde, Andrew & Scott for your help.

The pics show the wiring tangle with the extra wires for the city lights now used as DRL powered by the green foglight switch. There are also cut wires from back when the car had an auto Trans. The wire on the red fender cover goes to the reversing switch in the 5-speed.

 

[rsporsche]

so happy you got this sorted Drew ... its so great to have that kind of person as a resource nearby.

 

[stphers]

Glad that you got it solved but I would pick up another headlight switch. These fail both on the E9's and the 2002's If it acted up once, it will probably act up again

Thanks, Rick

 

[tferrer]

Great resource you have there. Let me know if you need another switch. I got one from Don but the plug on mine was completly different (euro 72) so perhaps the one I got from Don may be the one you need.

 

[adawil2002]

Glad it’s all sorted out, Drew. Dave knows definitely knows coupes.

 

[Stevehose]

If you're keeping the headlight switch I would disassemble and clean/regrease it. It's not difficult. I have a thread on this:

DIY - Rebuilding the headlight switch

Ok friends, here's another edition of kitchen table restorations, except tonight my wife has kicked me out of the kitchen so I will be cluttering up the back deck table while enjoying some vino. Anyway, these expensive switches can be rebuilt quite easily. This is my friend's switch, I noticed...

e9coupe.com

 

[Drew Gregg]

My electrical problems were solved this morning by David Masi. Dave worked for The Werke Shop in Illinois for several years taking apart and assembling the coupes brought into their shop for repairs and restorations. He has his own business now in the South Florida area working on classic Bimmers. He has fixed several items on my car that were botched by the restoration shop that had the car for almost 2 years. I had removed all of the trunk elephant skin to inspect the wiring and removed the lamps that were not working to try to isolate the short. It looked like the problem was in the headlight switch and I knew he would have the tool to correctly remove the switch from the dash.
Dave took everything apart including the pin block that plugs into the switch terminals. He used special BMW branded tools to remove the terminals. Then he powered up each circuit behind the fuse block. All of the lights that were off went on independent of the headlight switch. Then the switch was tested and blown clean. There must have been some dirt inside the switch that caused the short/blown fuse #2.
After all was put together,I stood behind the car while he put on all of the lights and blinkers. All worked. Then he put the car in reverse and asked if the 2 clear lights came on. And they didn't. What??? They worke

Great resource you have there. Let me know if you need another switch. I got one from Don but the plug on mine was completly different (euro 72) so perhaps the one I got from Don may be the one you need.

David just inspected the switch and dusted it off. He really didn't do his typical disassemble everything procedure. I would like to get the spare switch from you and source the special tool used to remove it from the dash. Here's a pic of the tool. Thanks for the offer! Drew

 

[tferrer]

My electrical problems were solved this morning by David Masi. Dave worked for The Werke Shop in Illinois for several years taking apart and assembling the coupes brought into their shop for repairs and restorations. He has his own business now in the South Florida area working on classic Bimmers. He has fixed several items on my car that were botched by the restoration shop that had the car for almost 2 years. I had removed all of the trunk elephant skin to inspect the wiring and removed the lamps that were not working to try to isolate the short. It looked like the problem was in the headlight switch and I knew he would have the tool to correctly remove the switch from the dash.
Dave took everything apart including the pin block that plugs into the switch terminals. He used special BMW branded tools to remove the terminals. Then he powered up each circuit behind the fuse block. All of the lights that were off went on independent of the headlight switch. Then the switch was tested and blown clean. There must have been some dirt inside the switch that caused the short/blown fuse #2.
After all was put together,I stood behind the car while he put on all of the lights and blinkers. All worked. Then he put the car in reverse and asked if the 2 clear lights came on. And they didn't. What??? They worke

David just inspected the switch and dusted it off. He really didn't do his typical disassemble everything procedure. I would like to get the spare switch from you and source the special tool used to remove it from the dash. Here's a pic of the tool. Thanks for the offer! Drew

Sounds good. To be sure we have a match, take a look at this thread of pictures of the spare I have from Don and the one I needed. There appears to be at least 2 types of these switches so lets not make the same mistake I did!

WTB: Euro CSi/CSL Headlight switch

Hi everyone - I'm looking for the correct headlight switch for my 72 CSL (Nov 72 build date). I bought what @sfdon and I thought would be the correct one but alas it's not. The switch on the LEFT (circled in GREEN ) is the one in the car and what I'm looking to buy. The one on the right is...

e9coupe.com

 

[mulberryworks]

I would like to get the spare switch from you and source the special tool used to remove it from the dash. Here's a pic of the tool. Thanks for the offer! Drew

It looks like the same tool that similar age VWs used for their light switches. I used to have one, decades ago with my VWs. It shouldn't be too hard to find.
Ah, here's one.

https://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=111941000

 

[Drew Gregg]

Sounds good. To be sure we have a match, take a look at this thread of pictures of the spare I have from Don and the one I needed. There appears to be at least 2 types of these switches so lets not make the same mistake I did!

WTB: Euro CSi/CSL Headlight switch

Hi everyone - I'm looking for the correct headlight switch for my 72 CSL (Nov 72 build date). I bought what @sfdon and I thought would be the correct one but alas it's not. The switch on the LEFT (circled in GREEN ) is the one in the car and what I'm looking to buy. The one on the right is...

e9coupe.com

We will pull my switch again to confirm the right switch in your pic is the correct configuration.

 

[eriknetherlands]

You can also unscrew them with a correct size Snap ring plier. If so, push hard so not to have it jump out and make scratches.



If you happen to have one already, it saves you buying a tool that you need only once..