Wiring identification

[Figoulu]

Hello all😄

I was about to reconnect my new horns while I discovered 2 original wires, badly cut and left like that…

I assume it could be a separate circuit for each horn as I figured out my original connection was  possibly wrong

Then I went back to the original wiring diagram to finally identify that my original wiring was correct, while I still couldn’t identify the use of the 2 remaining cables, despite looking at the same wiring diagram.

I read my ohmmeter while trying to play with the knobs, lights and everything I could test, but nothing came up…

So to sum up the whole story I have 2 wires that comes along with the horn cable. If somebody could tell 👍👍

I attached the pics with the colour codes of the said set of cables. Picture doesn’t tell all so…
One is black/ yellow, the other one is black/pink/yellow…

[lpeterssen]

Dear Figoulu

Horn cables are :

1. Black / yellow for positive signal coming directly from fuse box
2. black/yellow/rose coming from steering wheel switch carrying a negative signal.

You should have 4 wires in total since they make a lace up on the first horn to the left side.  Which mean they are connected in pararel

Best regards
Lp

[Figoulu]

Thanks but…

I guessed it could be like this… and so I have tested those wires whith the Horn circle switch and nothing happened on my ohmmeter while the other 2 originally connected to the 2 horns gave some positive results showing a good connectivity

Referring to the wiring diagrams… it seems that the connection is a serial one… at least on my document

Where is the truth ? 🤷‍♂️

[BobH]

Hello, as Leo says, the horns are connected in parallel, +12ve from the fuse and a negative (ground) from the horn switch to the first horn, and then paralleled from horn 1 to horn 2.  Not sure where you would test for continuity, better to test for power at each horn, when the horn switch is operated

[Figoulu]

Hello, as Leo says, the horns are connected in parallel, +12ve from the fuse and a negative (ground) from the horn switch to the first horn, and then paralleled from horn 1 to horn 2.  Not sure where you would test for continuity, better to test for power at each horn, when the horn switch is operated

Unless I misunderstood but what you described is serial circuit, not parallel, as you mentioned from horn 1 to horn 2..
The battery is disconnected but the ohmmeters tests are enough to state good or bad 😅

[BobH]

Definitely parallel, a series circuit only requires three wires, a +ve to one component, horn, lamp etc, then a single wire to the second component, and then a negative back to the ground via the switch.  If one component lamp or horn fails, then the other one will also stop working

Here's a simple diagram showing both circuits

https://byjus.com/physics/difference-between-series-and-parallel-circuits/#:~:text=Difference%20Between%20Series%20and%20Parallel%20Circuits%20%20,if%20o%20...%20%202%20more%20rows%20

[rwmastel]

I'm no electrician, but I'll vote SERIAL.  Because, in the wiring diagrams provided by figoulu, the power flows from the first horn to the second horn.  There is no way to bypass horn 1 and get power to horn 2.  In the educational link provided by BobH, the SERIAL example shows power flowing directly from light 1 to light 2.

Please, help the novice electricians understand how this is parallel in the M-B wiring diagram.  Once we all agree, then maybe we can move forward with the original problem of these rogue wires and figuring out what they are for.  Without knowing anything else about figoulu's car, I would wonder if they were from some old security system a PO installed.

[lpeterssen]

Dear Friends.

Bobh is right. THIS IS A PARALLEL CIRCUIT. 

The diagram shows so, as well.

A different thing is that the cables go first to HORN 1 On the left side of the car, and from there to HORN 2 On the right side.

FIGOLOU you will notice that on the cables coming on the main loom, for each color scheme you have one which is thicker than the other.  The thick one comes first and is connected in parallel to the next horn which is fed by the cable that is thinner.

So….

At the HORN on the left side….. for a LHD car)

2x cables in black/yellow. The thick one come directly from fuse box

2x cables in black/yellow/rose . The thick one comes directly from the HORN RING carrying a NEGATIVE signal.  The thin cable in parallel goes to second horn.

Best regards
LP

[lpeterssen]

A SERIES circuit will be IF:

1. First horn is fed on one side by positive black /yellow.
2. First horn second terminal that was not connected has a cable connecting it to any terminal on the second horn
3. Second horn receives on one side the cable coming from horn 1.
4. Second horn receive on the other terminal the cable coming from the HORN RING carrying a negative (-j signal

Best regards
Lp

[Figoulu]

A SERIES circuit will be IF:

1. First horn is fed on one side by positive black /yellow.
2. First horn second terminal that was not connected has a cable connecting it to any terminal on the second horn
3. Second horn receives on one side the cable coming from horn 1.
4. Second horn receive on the other terminal the cable coming from the HORN RING carrying a negative (-j signal

Best regards
Lp

Thanks Leo

This scheme is more explicit 😅😅

Thanks to all 👍👍👍

[lpeterssen]

Your welcome Figoulu…..

Your friend finally bought the new wiring harness?  Are you going to receive the used one as a gift?

Best regards
L.Peterssen

[Figoulu]

Your welcome Figoulu…..

Your friend finally bought the new wiring harness?  Are you going to receive the used one as a gift?

Best regards
L.Peterssen

I have it but he wants it back...
Anyway it was useful today... as I needed to double check what goes where...

[Figoulu]

Well...

I was happy to get back to my pagoda and thanks to your contribution, solve my issue...

I started by rewiring everything, and extend the lenght that was cut during the life of the car.
My technic was to replace the missing part by new wires with the right section, and put at the end the original wire with the correct color code, so it could stay consistent with the wiring diagram. Red for +, and black for neg. for keeping a sort of standard for the extensions...

[Figoulu]

I even could find the piece of loom that was cut off / prolonged with yellow cable...
Everything was removed cleaned / replaced...

[Figoulu]

From this point everything was clear...
After rewiring, I checked the continuity with my ohmmeter and pushed the horn ring. Everything was ok... but...

I put the battery back in the car and tested the pair of horns...
Something very weird happened as... nothing happened... without the key, with the key, and in various positions...

I then wired directly the + to the fuse #2... My suprise was that I heard the gas pump running, as it's normally wired to fuse #3 as far as I understood...

Pushing the horn ring was successful, once... twice but afterwards the horns were even running continuously without pushing the ring...

I tried many combinations with and without any reflexion (just to see if it works... ), double checked every contact, wires... even removed the horns from their bracket in case it was running permanently the negative pole... but nothing good at the end of the day. I couldn't make it run properly

I rechecked again and again... without the battery everything works perfectly with my ohmmeter. Since I put a source of power, nothing happens as normally I guess the horns are running without the ignition key turned. When I connect the + to the fuse #2, then I can push once or twice the ring, the horns runs ok, but then for some reason keeps running without touching the ring...

So I'm puzzled and very disapointed, cause I thought I could solve my issue easily...

Another "funny" stuff is that when I turn the key as if I wanted to crank the engine, the horns briefly runs...

I'm not enough an expert to solve it by myself... I guess it's a small stuff, at least I hope...

[lpeterssen]

Call Ghostbusters…..


That is why you need an expert like me to solve all the wiring harness issues…..

1. Pump running at which condition?   There is a known failure if you have the door open and your brake fluid sensor is bad, that causes to run the fuel pump in crazy occasions….,

2. Horn sounding all the time the problem should be on the horn pad switch….

Best regards
L.Peterssen

[lpeterssen]

Do not feel overwhelmed….

Work systematically ….

Isolate the problem……

The horn….

First disconnect the 12 pin terminal that goes to your steering wheel…. If that stops the horn from sounding the you know your culprit is from that point on….

Remember the horns are fed with 12v all the time the ignition is on, that mean will have energy + all the time the T15 circuits on the main fuse box are alive.


The switch to turn on or off the horn is on the steering wheel horn pad.  That supplies the NEGATIVE needed to complete the 12v DC circuit….

Enjoy you Sherlock Holmes activities…

Best regards
L.Peterssen

[Figoulu]

I will look  at that but…what I don’t understand is why it doesn’t work when I supply current and why it seems ok on my ohmmeter ? Additionally it was working before…
I have suspected a malfunctioning around the horn ring but my ohmmeter shows a correct continuity…

Btw my test with ohmmeter is when the key is at 0, meaning it might be a hot on the horn. Do you agree ?

[lpeterssen]

Exactly if the ohm meter shows a perfect continuity on the horn ring is because is bad.  ( I mean if you do not press it there should be no continuity)

The horn ring is a switch.  You should have continuity among both cables connected to it only when it is depressed.  When the horn pad is not depressed, there should be NO continuity among its two terminals.

The other question placed after the “btw”. Answer NONONO.

The horn ring FEEDS only THE NEGATIVE SIGNAL to the horns on the engine Bay Area.  Therefore it will supply the negative signal independent of the position of the ignition switch POSITION, since ignition switch only cuts POSITIVE feed to the main fuse box.

So…. The horns need two things to work, …..

1. Positive feed 12v that is available only when the ignition switch on the RUN position (therefore all circuits of the main fuse box energized

And

2. A NEGATIVE signal that comes from the HORN RING.  that negative signal is not interrupted by any way by the ignition switch, since GROUND on cars is available all the time as long as there is a battery connected on the engine bay.

Schlafe gut my friend

Lp

[Figoulu]

Misunderstandings again 😁…

1/ talking about continuity regarding the horn ring, was meaning that when I press it, my ohmmeter shows full continuity. In other words… it works, and independently from the key position

2/ this demonstration is made without power supply connected as when i connect the battery something wrong happens.
After a night of thinkings I believe that when I connect the battery and make the shortcut to fuse #2, it makes the mess. It might happen that the current flows by somewhere else as fuse #2 is connected with fuse #3 to #6…. So this might explain why my gas pump is activated and maybe other stuffs

I will remove fuse #2 and connect the battery to the lower pole of the same fuse #2 and see what happens

Another thing, the car is not 100% ready and « finished »so there are couple of other cables disconnected, that could also explain the mess

If it’s not clear I will make a video hoping it’s more understandable at this point

Thanks again for your very well appreciated help 👍👍👍

[lpeterssen]

Ohhhhh that is a different story…….

Not clear the part “when I make shortcut on fuse no.2”

Fuses 2,3,4,5,6 are all fed through the screw terminal attached to the hot side of fuse no.2. Hot side is where the dc current enters the circuit, I mean the supply …


All those circuits mentioned before are referred as T15 circuits, live when ignition is on.

Then current flows through each of the fuses to the particular circuit they supply.

So if fuse is installed on 2, current passes and brings power to whatever cables are attached to the output side of that circuit.

Same story for circuit 3, 4, 5, 6.

But this circuits are independent.

Best regards
L.peterssen

[lpeterssen]

Top screws on the fuse box are where each individual circuits are attached.  Lower screws is the supply part, before the fuses.

[Figoulu]

Thanks for your feedback
I'll try again coming week end, after all there's no reason it shouldn't work