1973 headlight wiring question

Drew20

Drew20

Well-Known Member
Site Donor
Messages
465
Reaction score
136
Location
Beaconsfield
Hi, I'm a new owner of a 1973 UK RHD CSL. There is a long list of jobs I want to do on the car and I'm going to be asking lots of questions over the winter lay-up. :)

The first job I'm planning is to get the headlights sorted. The wiring has been mucked about with by a PO and I would like to take all of that out and replace it with a set of 4 Cibie CSR 5 3/4" lights (I happen to have a set to hand) and a new high and low beam relay system.

My question is, is there a wiring diagram that covers my city-pack CSL? Just to see what should be there. I've done a bit of reading on this site and 1973 looks to be a transition year, and the wiring diagrams I found were US cars.

Another question, would my car already have high and low beam relays. On the wiring diagrams I've seen the high beam circuit has a relay, but the low beam does not. I also noted that there is only 1 fuse per circuit, ie if the low beam fuse blows then you lose both low beam headlights.

My "vision" is to bypass any pre-existing relays and add in fuses and double pole relays to both circuits
 
It shouldnt be too difficult. If you are not planning to have aircon or fog lights the existing three relay holders near the main earth point are a good place to start being near to the battery and main earth.
In my car the relays for the air horns and aux fan/aircon are behind the front N/S grille. P1020827.JPG P1020828.JPG
 
Cool thanks, helped me find the hi beam and horn relays

5BWfQZ8.jpg


Just out of interest, what is the metal rectangular "thing" next to the two relays? Marked Bosch on the top...

....and the orange plastic piece?

Cheers
 
Voltage regulator and orange test connection cover. Underneath it is a socket that, back in the day, repair shops could plug into to jump the starter, get rpm, etc. Don't lose the cover, it's unobtanium.
 
Drew20 said:
Cool thanks, helped me find the hi beam and horn relays

5BWfQZ8.jpg


Just out of interest, what is the metal rectangular "thing" next to the two relays? Marked Bosch on the top...

....and the orange plastic piece?

Cheers
Click to expand...
Strange you have the old style Hella round relays.
 
Stevehose said:
Voltage regulator and orange test connection cover. Underneath it is a socket that, back in the day, repair shops could plug into to jump the starter, get rpm, etc. Don't lose the cover, it's unobtanium.
Click to expand...

That would explain why the voltage reg didn't appear to have any connections to it, as my alt clearly is not original, being shiny and new looking. Thanks
 
Simufly said:
Strange you have the old style Hella round relays.
Click to expand...

Would they not be period for a '73 car? Round relays do look fairly ancient, but they do both still work

On looking at this I think I'll leave the hi beam relay alone, and just add a relay for the lo beam. There's even a space for another relay I can use, which I assume is for the aux fan (my car has no aircon, but it does have an aux fan...? another mod I guess)
 
Drew20 said:
Would they not be period for a '73 car? Round relays do look fairly ancient, but they do both still work

On looking at this I think I'll leave the hi beam relay alone, and just add a relay for the lo beam. There's even a space for another relay I can use, which I assume is for the aux fan (my car has no aircon, but it does have an aux fan...? another mod I guess)
Click to expand...
73 cars usually have the square smaller bosch relays.
 
I think they are correct, my '73 I bought from original owner in '84 had them. Your alternator is internally regulated (good) and they kept the old regulator for looks (also good). The third relay slot was for fog lights but I used it for the low beam relay and hid the fog light relay under the headlight access cover.
 
Liking all the engine bay photies, think I need to get my coolant header tank, power steering reservoir and brake servos painted up

Thanks for the help.

No doubt I'll be back soon with more newbie questions...
 
Here's an odd thing. Phase 2 RHD CSi.
Just been wiring in some driving lights (see other Driving lights thread) In the end I decided to piggy back onto the main beams. Well, pulling off the main beam relay revealed only three wires to the relay holder. A red power lead. 4x white main beam and an unidentified single grey or white lead. NO earth so the main beam relay has never worked, and yet the main beams do work albeit a bit dimly! Not that I can recall when I last drove it a night if ever. So all the power for the mains was going through the light switch and the indicator/ dip/main switch. not sure how but definitely NOT GOOD.
Also the red power lead was not to terminal 30 on the relay. Wierd.
Anyway moved the power lead to terminal 30, wired in an earth to 86 and the 4 white leads to 87. Put a temporary lead on to 85 and put it all back together. Ignition on lights on and main beam selected. Yep all four are on but the mains a bit weak though. Temporary lead 85 now to the battery and hey presto relay "click" and main beams now at full battery brightness. Progress.
Under steering column panel removed. Just by the existing fog light press switch there is a small unattatched loom, with three wires. Brown,(earth) a yellow with green trace and a grey/white
Was this the same grey wire as in the engine compartment? A quick continuity test proved that it is.
Ok so now we have the trigger for the main beam relay.
So the white/grey wire was fixed to the 85 terminal on the main beam relay.
Working back to the indicator/main dip beam switch where it is plugged into the main loom, a bit of fiddling with the AVO revealed that the flash and main beam was to pin 3 on the plug. By removing the relevant pin from the plug and making a joining cable to the unused white/grey cable of loom. we now have a trigger to the main beam relay.
Funny old thing it works.
 
Last edited:
Progress to date: I have taken the existing system to pieces and what a bodge I have found. The quad lo beam system has no relay, so than means 4 55w filaments are powered direct through the light switch. That's a lot of amps!

And the light buckets have been assembled in an odd mis-match, not sure why....

I've taken the buckets apart, de-rusted and painted them up and reassembled them as they should be, and the cities CSR lights fit perfectly.

Next step is the wiring, plan is for a dedicated fuse and relay for each lo beam filament, with supply direct from the alt, and cleaned up earths

I was talking to a garage who recommended HID lo beams. I did this mod on an E24 previously and it was so so bad. This was 10 years ago though. Is HID a common mod on this vintage of BMW?
 
HID lights are designed for projector style lights, installing them in a normal reflector light will yield a terrible beam pattern that will make all oncoming Road users instantly hate you.

I'm currently in the process of designing a wiring harness on the computer to use the original main and low beam triggers to run a new independently fused and relayed front light harness capable of running 4x100w bulbs to get rid of 40+ year old wiring that has been hacked countless times. Wiring looms and harnesses cost pennies and they have to be in top condition before trying to upgrade the bulbs.
 
Susquehana Motor Sports has a schematic of how to build a harness that will allow all 6 filaments to be lit on Hi beam. This in conjunction with halogen lights. I did this on my 81 e24 euro as follows..I wired the 2 seperate low beam circuits into one circuit and the same on the hi beams. Early euro E24s originally had a separate circuit for each light. I bought a relay for each circuit from them and wired it all together, from the fuse box on, using 20amp fuses on each circuit, hi and low beam, again all 6 filaments will light on hi beam. In addition for overkill, we wired a 30 amp circuit breaker into the system as well. None of the switches had to be changed. Susquehana is a distributor for Hella products and a great place to do business with. No affiliation with them.
 
Lots of good info there, yes I'd come across the Daniel stern site years ago. Good info on volts lost in the wiring having a big impact on light output. Lighting power proportional to volts squared and all that.

Plan is for two low beam filaments and four hi beam. Hi beam wiring is fine as is with the existing factory relaty set up, but low beam will get one relay per filament, independently fused and powered direct from the alt with 4mm gauge wire

Hi again Bert, we crossed paths on the big coupe site years back. I used to own an M90 engined E24, but sold it 6 years ago. Glad to hear you still have yours, I've regretted selling mine many times since.....
 
You must log in or register to reply here.
Back
Top