E32 Map Light Score & Question

[jhughes]

OK, I went through all the posts I could find on this and I'm still unclear on how to wire the E32 map lights into my 95 E34. These lights came off of an 88 E32- I pulled them myself so I'm positive I'm not missing wires- these are the factory harnesses, factory wires.

There are 3 wires. Red, Red/Brown, Brown. Brown runs through a switch and then to the map light bulb's "-" side. Brown is exclusive to the map light. Red is shared via a bus between both the map light's "+" side and the courtesy light's "+" side. Red/Brown is exclusive to the courtesy light.

So, they both share red, which I'm assuming is a positive feed. They then both have their own ground, brown for switched map, brown/red for courtesy. Assuming brown is ground, of course.

Writeups I've seen talk about a 4th wire for the map light but since the map light shares a bus with the courtesy light I don't see how you could give it it's own "+" wire.

Ideas/thoughts?

BTW I think I saw another set of these at the boneyard if anyone is interested.

http://farm5.static.flickr.com/4113/5192868168_35f17786ce.jpg

[jhughes]

So here's what I'm thinking. Based on the schematics in the Bentley manual there are two completely different circuits for these lights which would indicate 4 wires (as others have mentioned). Since this particular light shares a positive bus between the courtesy and the map light (looks like an "S" of metal in this picture and contacts the + side of the map bulb here) I'm thinking perhaps I just cut that bus in half and soldier on a new + wire for the map light. That way the two bulbs would be on completely separate circuits rather than sharing a ground (or a + in this case). Thoughts?

[Layne]

They are on seperate circuits. Power is on all the time, and they are grounded independantly. The map light is grounded by the switch, and the courtesy light is grounded by the door switch (most likely by way of a module/relay).

[jhughes]

I shall saw the bus in half then, and add that 4th wire.

[dhcomp]

I shall saw the bus in half then, and add that 4th wire.


Wrong. Its been months since i did mine, but IIRC, the 4th wire is there, its just not in the plug. Remove the whole trim panel, and you will find it.

I did NOT have to tie 2 wires together into 1 at any point.

Match up the 3 colors you have, and find the 4th one, i think it was purple.

Hack off stock harness, splice in new light harness, and hookup.

Good luck!

[Layne]

What's the sense in adding a 4th wire? You only need 3 wires to make 2 circuits.

[LouieD]

The early lights are only three wires. Sometime in 1990(IIRC) BMW added the 4th wire. It's in your best interest to source a set of lights with the 4th wire. The extra wire is a key on, so if someone leaves the map light on it will turn off with the key. On 95 cars and all Tourings, BMW used the small 4 wire connector. When you source the 4 wire lights, grab the car side of the wiring and snip off the small 4 wire connector in your car. Splice in the early larger 3wire + 1 and you will have a PnP set up or you can solder/crimp with no plug. Make sure to turn off your front center courtesy lamp prior to cutting wires at the back. You'll avoid blowing the fuse and since you will probably have the doors open for the length of time you are working, the GM will turn them off to avoid battery drain, and them you have to wait for it to reset.

[jhughes]

OK, let's clear this up because I think there's some confusion here.

This 1988 E32 light (actually has a 1987 build date on the tag) has 3 wires to create 2 circuits. This is because both the map and courtesy bulbs share a common "+" bus, as you can see in the detailed picture of the light.

The E34 wiring has 4 wires, offering the map light its own separate + (and it's own -, actually). There would be no place to put a 4th wire on this light since it ONLY has 3 wires BECAUSE both bulbs share a COMMON + wire via a metal bus. In order to adapt this light to the E34 wiring harness I'd like to separate the + side of light by bisecting the metal bus so that each light has it's own + and it's own - just like the factory wiring diagrams tell me its should be fed.

However, if you don't think I need to go this far, I could wire it such that both lights share a common ground and keep it 3 wires.

[sfgearhead]

Having the map light shut off when the car turns off is very nice, my daughter would have killed our battery multiple times as she likes to play with the light when she gets bored.

[cornflakecwl]

Wrong. Its been months since i did mine, but IIRC, the 4th wire is there, its just not in the plug. Remove the whole trim panel, and you will find it.

I did NOT have to tie 2 wires together into 1 at any point.

Match up the 3 colors you have, and find the 4th one, i think it was purple.

Hack off stock harness, splice in new light harness, and hookup.

Good luck!
+1 been almost a year since i did mine, but I didn't have to join any two wires together on either side myself either. The wires are behind the panel as stated.

[LouieD]

No confusion. You have 3 wire lights and a four wire car. Get the correct lights and it's pseudo PnP for your application. You can use the three wire lights, it's just that your map lights may stay on after shutting off the car because both bulbs for the 3 wire lights get their power from a constant source.

[jhughes]

The main point was my grand plan to convert the lights to 4-wire versions by cutting that bus and soldering on the 4th wire. Nobody has commented on that, yet I think it makes perfect sense. It's not like I can run to the store and grab 4-wire versions of the lights. I'll post my results later. There is no way this 3 wire version will work properly without surgery.

[IT Jedi]

I'm about to do this too. Subscribed.

[barry8108]

I have several sets of the light with the 4 wire set up. I put a set in my 540, once u hook it up to a set of plugs it's just plug and play. Takes about 15 min of work and no soldering.

[acssilhoutte]

this is the rear map lights rite? what's the different with the e34 one? mine has this one too in the back.. it came from standards i think..

[attack eagle]

OK, let's clear this up because I think there's some confusion here.

This 1988 E32 light (actually has a 1987 build date on the tag) has 3 wires to create 2 circuits. This is because both the map and courtesy bulbs share a common "+" bus, as you can see in the detailed picture of the light.

The E34 wiring has 4 wires, offering the map light its own separate + (and it's own -, actually). There would be no place to put a 4th wire on this light since it ONLY has 3 wires BECAUSE both bulbs share a COMMON + wire via a metal bus. In order to adapt this light to the E34 wiring harness I'd like to separate the + side of light by bisecting the metal bus so that each light has it's own + and it's own - just like the factory wiring diagrams tell me its should be fed.

However, if you don't think I need to go this far, I could wire it such that both lights share a common ground and keep it 3 wires.

You've got the right Idea

ANd I second the idea to convert them to 4 wire. For exactly the reason stated.

But if you dont want to, just wire the single positive to the constant + on your 4 wire plug, and the grounds as appropriate. ( i think the colors match, but read the DIYs to be sure)

I didn;t even bother with a plug when I did mine. I cut both plugs off & used bare (uninsulated) butt connectors and heat shrink (reduction of failure points). There is more than enough length on the wiring harness to pull them out for service.
And if you need to remove the C Pillar cover later, you just pull them out, turn em lengthwise and feed the light housing right back thru the hole.


this is the rear map lights rite? what's the different with the e34 one? mine has this one too in the back.. it came from standards i think..

later NA spec e34s didnt have the map light. just a big courtesy light

[acssilhoutte]

later NA spec e34s didnt have the map light. just a big courtesy light

owwhh i see.. :)

[jhughes]

Ran to the yard today and pulled a set off of a 94 740, 4-wire. As predicted they are identical to the 3-wire variety except that that strip of metal shared between both bulbs is actually 2 pieces of metal and the the 4th purple wire is attached to it. I guess I have an extra 3-wire gray set available if anyone wants them.