Headlight switch, missing wire or broken internal?

[flagoworld]

I am debugging my buggered dash lights. They've never worked for me. The rheostat appears to work fine, measuring it with a multimeter. I traced some of the wires around and here's what I'm getting:

 

The spade circled in blue is the output voltage to the dash lights

The spade circled in green is the ground from the rheostat

The spade circled in red is the power for the rheostat. It appears to make a connection to the rheostat when the switch is pulled out (on).

 

But if you look at the plug, there is no wire going to the spade I would expect to power the rheostat. Am I missing something? Or should that connection be made internally?

 

(note i am seeing connectivity to the light bulbs and variable resistance through the rheostat, but no voltage is being switched to the rheostat)

 

 

Edited October 23, 2018 by flagoworld

[AustrianVespaGuy]

I don't think the terminal you have circled in red should have any wires or do anything, no.  My guess is it's just 'extra' on the available switch BMW chose to use, so don't worry about that one.  The supply voltage SHOULD be coming from the red wire (terminal 30) with the car switched off, AND from the green wire (terminal 15) when the ignition is switched on. You are also correct that the grey/blue wire (terminal 58b) goes from the adjustable rheostat to the dash bulbs. The grey/white wire (terminal 58s) I think should go back to the rear to power the tail and/or license plate lights or something like that, but afaik should be separate from the dash cluster lights.

Hope this helps!

[flagoworld]

Are you sure? I’m seeing 8 wires in that diagram and I have only 7 wires going to spades. The 8th spade is disconnected.

 

I opened up the switch and check it out. The wiper for the rheostat spade definitely is not connected internally and looks like it should have a wire going to it.

 

Not seeing any loose wires under the dash ?

[flagoworld]

If someone with a newer style switch could pop out their gauge cluster really quick and take a peek at that switch connector that would help I think.

[AustrianVespaGuy]

Sorry, you're right in that there should be 8 wires! What terminal number is that labeled as, is it 58S? Can't quite tell in the pic, but I think that's 58S which should have that grey/white wire going to the rear lights. Can you compare your wire colors to the diagram and determine which one is missing? And what year precisely, so that I can double check we're looking at the right schematic?

Edited October 23, 2018 by AustrianVespaGuy

[flagoworld]

Yeah the red circle is 58S and the blue circle is 58b.

 

58S is wire 129 in your diagram. Where do you see where that's supposed to come from?

[flagoworld]

Also, I found this one picture of someone else's connector when searching and it looks like there's no wire there. I'm really confused how this could be. You can see very clearly from the internal workings of the switch that there should be a connector here.

 

[AustrianVespaGuy]

Sonofabitch! Sorry you were right all along! Looked closer at your opened up switch and the diagram and yes, there's break, terminal 30 does NOT directly supply the rheostat.  Instead, +12V from terminal 30 (red wire) goes out on the grey/green (58R) to fuse #8, and then the grey/white comes BACK from fuse 8 to terminal 58S which is the +12V for the rheostat/dash lights.  I guess this makes sure the dash lights are all fused, but jeez BMW, that one's a bit weird!

Anyway, do your RH parking lights work? If so, then everything else from fuse 8 is still OK, and you just need the wire from the fuse to the switch and then your dash lights will work again.  Looks like it should come from that junction 62 which is probably under the dash on the drivers side.  In a pinch (or as a test), you can always just jumper from either terminal 58L or 58R to the missing 58S and everything will work, albeit now the dash light circuit will no longer be fused, so do mind that.

73 2002 color wiring diagram.pdf

[flagoworld]

Very telling! My right rear parking light (that's basically the running light, right?) has always been out too. Never bothered to try to figure it out. The hazards and brake lights work, but the red running light in the right rear does not!! Looks like this may be connected!

 

Thank you! This diagram is also much better than any of the ones I have. Awesome.

 

Now I just have to figure out where the hell that wire went, because I see no such wire under the dash. ? 

Edited October 23, 2018 by flagoworld

[AustrianVespaGuy]

So finally had a chance to run down and look under the dash on my car for you, and interestingly, my '75 is different from BOTH the '73 (diagram that I normally use and sent you) and the '76 which is the same, and in fact has ONLY 7 wires!!!  So exact year does matter greatly! Dug up the exact schematic from the tii registry and has the grey/white wire coming from fuse 8 goes in at terminal 58K instead of 58S.  From you picture, it looks like yours is the same way! Fortunately, both the grey/white and grey/blue wires are easily located at the three terminal connector just above the pedals, posting a shot of mine below for you.

 

 

['76mintgrün'02]

I am not sure whether this will be of any help, but the three prong connector that you recently plugged your fuel pump into (I believe) has two other connections that are headlight related.  The one you used is keyed power, the one in the middle comes on with the lights and the one on the left is dimmed lights. 

 

(I used the left one to light my new gauge)

 

I have no clue how all of this is tied into the light switch, but it is part of the equation.

Tom

 

EDIT... gotta be quick around here!

Edited October 23, 2018 by '76mintgrün'02

[flagoworld]

My 3-prong connector has nothing except the fuel pump connected to it. According to the diagram you linked, that seems correct? I'm not automatic so there's no "selector level gate".

 

I see you guys both have other wires in there though...?

 

**clarification: I see all the wires coming together on the female end of the connector, but the only other male end plugging in is the fuel pump I installed. The connector itself looks the same as your guys', just without the red/white/black wires plugged in.

Edited October 23, 2018 by flagoworld

[Mike Self]

While it doesn't have anything to do with the dash light function, the difference between the 73 and 75 headlight switch wiring may be that on US & Euro 73s, with the ignition off, selecting a right or left turn with the turn signal lever  will light the left or right parking and tail light.  That means that the current supplying those lights have to be separate on the light switch. 

 

US squarelights don't have that feature so current flow to left and right side lights don't have to be separated.

mike

[AustrianVespaGuy]

Right, look closely at the B/W schematic I posted. GN/WS was originally for the tii fuel pump (unused on normal 02s), and the other two I think were always 'empty' from the factory.  But they're great points for additional accessories (perhaps the original intention?) but coincidentally, they use just the two wires that you care about for your problem!  The GR/WS is the +12 supply (from fuse #8 ) for the RH parking lights and dash lights, and the GR/BL is the dimmed output from the rheostat that goes to the dash lights! So put your VOM on the center GR/WS and see if has +12V.  If it does, then just run a new wire from the empty terminal there to 58K on the light switch.  If it doesn't, then check/replace fuse 8 and that'll probably put you back in business.  If neither of these work, report back and we'll still get it!

Edit: to answer your other question, we both have other 'stuff' plugged in there because that's things we've added and used those convenient unused connectors under the dash to supply power to our additional gauges, O2 sensors, stereos, etc.

Edited October 23, 2018 by AustrianVespaGuy

['76mintgrün'02]

Yup.  That is where my AFR is taking power... and yours can too!

 

Tangents:

FWIW the LED in my gauge does not tolerate dimming and might as well be using the  middle plug.

Otherwise, if I want to dim the dash lights, the LED will go off completely.

 

(fwiw the gauge comes with two lighting options, white and amber.

I will be trying the amber light soon.  The white is bright, compared to the cluster).
Tom