Brake lights

[jan lauwers]

Hi guys,

I am trying to repair the brake lights, and I am facing a little mystery. I thought that I had found the root cause since there was a poor connection in the female connector that is sitting on the brake pedal switch. As a test, I bypassed the brake pedal switch by connecting the 2 wires in that female connector, and I still don't have brake lights. (contact ON, and bulb is OK). I don't understand that. Moreover, when I look at the elec scheme (here attached) I should see 2 wires that are red-black in the female connector. #23 is the pedal switch. In my car, however, I see a red-black and a brown-black wire.
When I remove fuse 5, and contact on, I still have current on the red-black wire, which again, I don't understand. With fuse 5 removed, there should not be any current, no?  I have taken the pedal switch out and it works OK. 

Any thoughts on this, please?

Then, one more general naive question. When you remove a fuse and measure the resistance between the 2 ends of the fuse holder, I thought that it should always be infinite, since the fuse should be the only connection. I am finding out that this is not always the case. In my car, most empty fuse holders show a connection between their 2 ends. Again, I don't understand that.

Sorry for my ignorance, guys, but I'd like to know what I'm doing wrong.

Thanks for your help,

Jan

[EeVeeWee]

When you remove fuse #5, then there must be (around) 12 Volt at the plus-side of the fuse holder and the other side 0 Volt. If there is still some voltage at the other side, I guess there must be a problem with earth connection(s).
That may also cause the problem with the brake lights.

[jan lauwers]

yes I have 12V on the 2 socket ends with fuse 5 removed.

[BobH]

Hello Jan

The only brown black and red black wires i see on a schematic are on the kickdown switch, so maybe something has been crossed in the past, have a closer look at both switches, particularly if you still have power when fuse 5 is removed

With regard to measuring across a fuse, this won't actually achieve anything, unless your meter is on "Amps" and then you'll measure the current drawn.  A circuit is effectively a loop, containing a switch, a fuse, and the appliance.  When you remove the fuse and replace it with a meter set to ohms, you're simply completing the circuit, not actually measuring anything. 

See how you get on

[Pawel66]

Jan, I am not a mechanic and I am sure there are more knowledgeable Members here, but a couple of points from me:

1. I think we should not be posting this wiring diagrams, they are proprietary, we all know them and there is no need to post them. Better remove it.

2. Has this arrangement you have worked before and it just went bad?

3. I would probably start from sorting the wires. On the plug that goes to switch you should have
- black/red/violet wire that is powered you should have continuity between the female connector in the plug and fuse 5 outgoing side
- black/red that is not powered - this is the one that goes to lamps. You should have continuity between the female connector in the plug and the bulb + socket.
- is there a ground on bulbs sockets?

4. Since you have some other colored wire, try perhaps to track where it goes.

5. If you have voltage on red/black wire with fuse 5 removed, it takes voltage from somewhere (if it is connected as per wiring diagram). Is it with ignition on or off? This may lead you to where the voltage is coming from. Anyway, if the other wire is going to fuse 5 and this red/black wire gets voltage from somewhere, lights should work if ground in the lamp is ok, back to continuity check in point 3.

6. Depending on voltage present with ignition on or off, there may be various suspects of where this voltage is coming from. My suspects would be 12 pin connector or lamp.

7. The other way to look for where is the unwanted voltage coming from could be to remove other fuses one by one and see when it disappears.

I would start from sorting the wires.

[BobH]

Apologies all, senior moment, my brain read "reverse lights", not "brake lights"!  i've removed most of my post as it will only confuse

[Pawel66]

BobH, I think you brought a very good point with the wires mixed between switches. I was looking for it myself, did not find anything, but then - I did not look at the separate diagram for automatic.

I think it is very likely that someone mixed wires on these two switches (even though one is in the cabin, one is under the floor).

[Cees Klumper]

Did your brake lights ever work but go out one day?

To check fuse connections, I always measure the voltage on them: multimeter ground to some known good ground, and the positive probe to the ends of the fuse holders. With fuse in place, obviously we want to see battery voltage (not much less, or you have an indication of voltage loss and so resistance somewhere between the battery and the fuse) on both ends. With fuse removed, only one side should have battery voltage.

[lpeterssen]

Dear friends

I agree with all previous comments regarding that a female two prong connector with a red/black wire with another brown and black definitely belongs to a kickdown switch.  If that is the case it should be energized on the red/black wire only while the fuse no.3 is in place.

That sub branch comes out of one that connects to the foot operated high/low beam switch. I mean go on same route.

It is right that the brake light switch is fed by fuse 5 and derivates from main harness branch just after the ignition switch connector.  That branch should have one black/red/violet wire (input) and one black/red wire which later goes to the 12 pin connector that interconnects main harness to rear harness at driver side footwell.

My guess is that this particular car may have been in the past an automatic car.  And now it is a manual transmission and therefore the 4 wires that go to automatic transmission have been chopped since are no longer needed.

That is the only logic explanation that comes to my mind that the connector with terminals for a kickdown are now attached to a brake light switch.

Nevertheless more clues are needed to solve the puzzle.

Best regards
Leonardo Peterssen
Www.Wiredoktor.com

[jan lauwers]

Thanks, Leonardo,

You are absolutely correct, my car has been transferred from Automatic to 6 manual gearbox. You're my hero. Now at least I know that the elec scheme that I was looking at is not applicable to my situation.

I am away for holidays now, but as soon as I return home will continue my search. It is also correct that the black-red wire that I see in the female connector gets current from fuse 3 not 5.
So, does that mean that I should now be looking for another female connector somewhere hidden in the mess of wires under the dash? Did my mechanic simply swap the 2 female connectors?

Anyway, thanks a lot for your help everybody, I will report back about my progress.

Jan

[lpeterssen]

Dear Jan

Yes you are correct. In the mess of cables of your main harness should be another two prong connector which is misplaced that carries the correct signals to drive your brake light switch.  It is a branch near the one that goes to main ignition switch.

Look for one with the following color coding:

1. Hot by fuse 5, line BLACK main color with red and violet stripes
2. Output cable, line black main color with red stripe that should have continuity to one line in the 12 prong connector at driver footwell

Also you should have trouble with the reverse light switch as the position on automatic cars and manual transmission ones is in quite different places.

You have also to check if some lines which are used on an automatic cars were properly disconnected at fuse box.

Write me directly if you need further advise.

Best regards
Leonardo Peterssen
Www.wiredoktor.com

[jan lauwers]

The problem is now resolved. The 2 female connectors, the one for brake lights and the one for AT kick down, had been accidentally swapped. Thanks for all your help, gentlemen.

Jan