E30 Electrical questions - What are things in this photo?

AlanCobb · Feb 8, 2004

Hi,

I've got a 1985 - 325e. I'm thinking about upgrading to
CIBIE headlights. This might also require adding
additional heavier wiring, relays and fuses.

When looking at the existing wiring, I can see a big +12
volt wire coming from the battery in the trunk up into the engine
compartment. There it attaches to a "terminal" on the left
side of the firewall. I'm trying to identify the details of
that "terminal". Please see the attached photo.

Two questions:

1) Points C and D measure +12 VDC as expected, but why don't
points E and F also? What is their purpose?

2) A is the big +12 wire coming from the battery, but there is also
a smaller wire at B that seems to simply run in parallel to the main
+12 wire. What is the smaller wire? Why run this separate additional
wire right next to the main +12 wire? Why isn't all the current
just pulled through the one big wire?

Thanks,
Alan Cobb

bichmgnt · Feb 10, 2004

Which Cibie lights are you getting? I just put in the CSRs and they're fantastic.

All I know about that power block is that you don't want to mix up the wires that go to it.

I'm assuming you want to have a more direct wiring path to the lights so they're brighter. I wouldn't bother. Your lights are already switched by a relay in the fuse box so your path is relatively short with wiring that should be heavy enough to the lights. Besides, if you rewire the way I think you want to the lights on your status panel will come on every time you switch the lights on.

The real question is are you installing H1/H4 lights that would be similar to your current lights (high beam light has a single filament while the low beam light has two filaments - a low beam, and a high beam filament that complements the high beam light) or something similar to the CSR lights where the low beam has only one filament that stays on when the high beams are on. Which you get determines what wiring changes you have to make. In my case, it was a relatively easy matter to rewire a single wire in the fuse box to make the lights work correctly and retain the functionality of lights on the status panel.

If you really have an issue with low voltage at the lights you can always install a slightly hotter voltage regulator that will boost your voltage a bit.

Steve

AlanCobb · Feb 10, 2004

Upgrading headlights CSR or non-CSR Cibies

Hi Steve,

I hardly ever use my high beams so I was just going
to replace the lows. To save money I'm thinking about
getting the non-CSR Cibies. They still have the better
euro pattern, but aren't quite as good as the CSRs.
Daniel Stern (http://www.danielsternlighting.com)
has the 5.75" round CSRs at $99 and the similar non-CSR
Cibies at $56.

The $56 units have both high and low filaments inside
them, so they can just be plugged in to replace my
wimpy stock sealed low-beam units, with no other
changes required.

Stern's website (and others) seem to make a big deal
out of using fatter wires to minimize the voltage drop,
but I guess I'll skip that first and see if they were
bight enough as-is. Sound reasonable?

Are there any downsides to getting a slightly higher
voltage regulator?

It would be nice if there was a website with "light-tunnel"
pictures comparing the Cibie CSRs and Cibie non-CSRs.
If I could see a big difference I might spend the extra
cash

.

Thanks for your input,
Alan

xLibelle · Feb 10, 2004

E and F are just mounting bolts, they have nothing to do with the circuit as they bolt to the frame, and them touching anything else in the pic would be a bad thing.
If you want a direct connection, just use either of the places you read 12 volts from.

AlanCobb · Feb 11, 2004

Ok, thanks xLibelle. That makes sense about the mounting bolts.

Kirby · Feb 11, 2004

I am not familiar with the specifics of the BMW wiring, but I have seen the Dual hot wire in a number of cars, it's fairly common. In those cars the purpose is to provide isolated power sources - one for the starter, alternator and other high power devices, and another for some or all of the accessory power. Without getting into details that excite only engineers like me, even though they go to the same battery, it reduces electrical noise, voltage drop, etc. Typically those two wires would be connected at the battery but NOT connected together at te power terminal block.

One specific example would be that isolating the radio power circuit from the alternator power circuit will reduce alternator whine on your radio.

I also agree with XLibelle that those are mounting bolts. For lights, you want to most definitely connect to power from the larger cable.

bichmgnt · Feb 11, 2004

I don't know how much difference there is between the CSR and non-CSR lights. I got the CSRs from Stern Lighting when they were a little cheaper and he told me they were going up so I got them right away. You might find that the old high beams look dingy compared to the new low beams.

I do like the CSRs and having the full set I see way farther down the road than I used to. With high beams on it seems almost unlimited. I haven't felt it necessary to upgrade to higher intensity bulbs in any case.

XLibelle - I love that quote. Is that for real? When/where did Bush say that?

Steve

mjbst111 · Feb 12, 2004

if he really said that i'm sure he was kidding.

AZRobert · Feb 12, 2004

I don't know. Have you ever seen this site

http://slate.msn.com/id/76886/ [hah]

mjbst111 · Feb 12, 2004

but they also quote him on this one like its a redicules thing to say:

"More and more of our imports come from overseas"

Its a pretty legit thing to say isn't it?

There can be reasons to say certain things that i'm sure they don't take into account. But just looking at the quote it is pretty funny.

Pretty good site!

AlanCobb · Feb 12, 2004

More on "mystery" wires

Hi Kirby,

Yes, there would not seem to be a reason to run
two wires in parallel if they both connect to the
same points at each end.

Actually I'm not really sure they _are_ connected in
parallel. I don't know where that smaller wire at B
goes, nor where the similar small "parallel" wire
coming out of the battery goes. Both wires quickly
go into the inards and can't be traced. Maybe they
aren't connected. (Yes, I could disconnect one end
and use another long wire with my ohm meter to test
that hypothesis).

I was just hoping they were "well known wires" that
somebody could easily identify

.

Alan

AlanCobb · Feb 12, 2004

Dual parallel feed wires from battery

Hi Kirby,

You were right. I disassembled the terminal block a bit
more. See new 60KB JPG photo at link:
http://home.jps.net/~alancobb/BMW_E30_BatteryCable_Firewall_Detail2-640x480-60KB.jpg

To verify that In-1 like In-2 is coming from the
battery in the trunk I disconnected In-1 from Out-1 and
used an ohm meter to measure the resistance between the
disconnected In-1 and In-2. It measures 0 ohms which
means that In-1 and In-2 must come in parallel all the
way from the battery in the trunk.

At the terminal block on the firewall In-1 and Out-1
are connected to each other, but electrically isolated
from everything else on the terminal block. The huge
In-2 cable feeds Out-2A (starter apparently) and Out-2B.

Out of curiosity:
I wonder where Out-1 goes in the wiring harness?

I still don't understand why it's necessary to run
the two wires in parallel from the battery. Wouldn't
the huge main wire (In-2) have such a low impedance
(basically resistance) that its firewall end would always
be at "almost" an identical voltage to the end at the
battery? Maybe it doesn't take much impedance to make
a difference? (I started out as an engineer before I
got into software [:D]

).

Alan

bichmgnt · Feb 12, 2004

mjbst111 said:

The reason it's ridiculous is because ALL of our imports (except Mexico and Canada) come from overseas. Always. No matter how much or how little. He might as well have said all our imports come from outside our country.

George W. Bush - Master of the Obvious.

My favorites are when he talks about education:

"[T]he illiteracy level of our children are appalling."—Washington, D.C., Jan. 23, 2004

I sometimes wonder how are his illiteracy level.

But I dont think he said the ham sandwich thing. That was a joke Conan O'Brien used on his talk show.

Steve

Kirby · Feb 13, 2004

Re: Dual parallel feed wires from battery

AlanCobb said:

The smaller wire most likely feeds the fuse block.

They design goal is to keep noise and voltage drop caused by the starter, etc. away from sensitive electronics. The starter can draw 50 - 125 Amps when first cranked. With that current load, there will be a voltage drop even with a heavy cable. I haven't tried it, but you probably might see only 10 - 11 volts at the starter when cranking it, partially due to voltage drop on the cable.

An interesting test would be to crank the engine and measure the voltage between the smaller wire and the larger wire. That would indicate the loss in the large cable.

mjbst111 · Feb 13, 2004

(except Mexico and Canada)....

bichmgnt · Feb 13, 2004

mjbst111 said:

Here's the whole quote:

"It is clear our nation is reliant upon big foreign oil. More and more of our imports come from overseas." Beaverton, Ore., Sep. 25, 2000

Neither Canada nor Mexico are big exporters of oil to us. It's clear he's talking about the Middle East and Europe. He is definitely not saying we are getting less Mexican oil and more overseas oil. He's trying to say we are importing more and more oil from overseas which is different than what he said. But he doesn't know how to put sentences together that make sense. He's not too bad when he has a speech in front of him. But when he's talking extemporaneously he makes up words (embetterment), he mispronounces others (nucular instead of nuclear), and generally puts his mouth on autopilot while hoping something good comes out. He's good at talking he's just not good at making sense.

Steve

mjbst111 · Feb 13, 2004

interesting, thanks for the whole quote.

now that i know what he was talking about instead of inports in general i can see the messup.

AlanCobb · Feb 15, 2004

Re: Dual parallel feed wires from battery

Kirby,

The conductor in the big cable from the battery looks to be
about 12mm in diameter. According to this wire table
http://ohm.bu.edu/edf_info/info/wire-resistance.html
that means it should have a resistance of about 0.062 ohms
per 1000 feet. The cable is about 11 feet long so that's
about 0.0007 ohms. 125 amps through that would drop only
about 0.09 volts. That's < 1% of 12 volts. (Hopefully
my data and math above are right).

I did the test you suggested and for a cold start the
voltage from the end of the little cable to the big cable
seemed to peak at about 0.2 volts just for an instant.

So it's still not clear to me what having the little
wire in parallel achieves.

Alan

Kirby · Feb 16, 2004

Check the article below, with particular attention to the bold sentences. From the viewpoint of the article, using a single wire would be a 'bus'.

===============
Alternator whine can also be caused by poor electrical connections, especially at the battery. Normally, the low impedance of the battery keeps the electrical circuits at a DC potential. (Impedence is simply resistance to an AC current.) Any AC ripple voltage is absorbed by the battery. Thus, the battery acts as a big ripple absorber.

If the battery provided zero impedence (i.e., a short-circuit for AC current), alternator noise could not occur. In the real world, there will always be some impedance. But the lower it is, the less ripple voltage there will be.

Let's assume that the battery positive terminal is corroded. Although DC resistance as measured with an ohmmeter may still be low, the high-frequency resistance (i.e., impedence) may be very high. The higher this impedence, the greater the ripple voltage on the bus and the more whine you hear in your radios.

Circuit impedance can be lowered by making sure the battery posts are clean and making good contact. DC resistance should be less than 0.01 ohm...virtually zero. Also check the alternator ground connections, including the engine grounding strap. DC resistance between the alternator and the negative post of the battery terminal should be as low as possible.

The ideal low-noise circuit would have the alternator power output going directly to the battery's positive terminal. This dumps ripple voltage into the battery, where it is absorbed. The radio power lead would also go directly to a pure DC source, the battery.

If the alternator power lead and the radio power lead connects to a bus, then voltage ripple can go from the alternator to the radio power lead. The amount of voltage ripple at the bus depends upon the impedance between the bus and the battery. This impedance is higher than at the battery.

AlanCobb · Feb 16, 2004

Kirby,

Thanks for providing the addition details.

That makes sense about ripple coming from the alternator.
Now I'm curious where that smaller "parallel" wire is
actually going... But probably not curious enough to try
to find out. It sounds like the radio might be the main
place it goes.

I'll just be happy if my new Cibie headlights are good and
bright when they get here

.

Thanks again,
Alan

E30 Electrical questions - What are things in this photo?

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