10 replies to this topic

[unburntfuelinthemorning]

I am fitting a dim dip system to my Mini.  I am having trouble identifying which terminals are which on the Lucas relay as the terminals are not marked.

 

Having taken the cover off the relay and inspected the circuitry inside I have worked out the terminals to connect the resistor, and the two dipped headlight (blue/red) wires (from the switch and to the headlights) to, so that's three out of seven. 

 

I have sketched out the circuitry onto paper but it has two transistors with unmarked terminals, two diodes with unmarked polarity and four resistors and I am struggling to understand the current flow in the circuit.

 

So I need to know which terminals to use for earth (black), fused ignition live (green), sidelights (red), and headlights on (blue).

 

If someone still running the system could have a look at theirs and even post a picture of the wiring and terminals that would be greatly appreciated.

[cal844]

Why do you want dim dip? It never became law so I'd not fit it

[unburntfuelinthemorning]

I like it. 

[Ethel]

I like it too, though you could do similar better with modern electronics.

 

Had a look for you. Not a Mini but colours may well be the same.

 

Looking at the pins with the mounting clip lowest:

 

Red - Red/Blue - Empty

Brown/White - Blue - Black

White - Red/Blue - Empty

 

 

Also found this, which might help translate a wiring diagram

[unburntfuelinthemorning]

Thanks Ethel, that diagram with the terminals numbered did the trick.  Wired it up and it works perfectly.  The Mini and Metro Haynes manuals I have don't number the relay terminals in the diagrams but luckily I'd also kept a Haynes manual for the Montego I had and they did number them in that one, knew it'd come in handy one day!

 

How would you do this better with modern electronics?

[Ethel]

Probably the simplest would be to squeeze in some led stop/tail bulbs to replace the sidelights and use the stop part for the dimmed headlights with a crossover relay switched by the ignition.

 

For closer to the original you could use a PWM motor speed controller in place of the ballast resistor. Haven't tried it, but don't see why you couldn't just switch the dip in parallel on top of the dim as there'd be no voltage drop like the ballast resistor creates for dimming.

[Ethel]

Did you work out what's what?

 

From the colours I'll guess:

 

2 & 8 one to the headlight dip beams, the other from the column stalk

 

4 is the supply via the ballast 

 

5 is the supply from light switch and it's basically a cross over relay to connect either 5 or 4 to the headlights

 

1 senses the ignition is on and 7 senses the sidelights, having both live will switch the relay to 4.

 

With whichever of 2 or 8 is from the stalk live the solenoid will default the other back to the normally closed terminal 5.

 

6 is the earth for the switching circuitry.

 

 

So it could be having dim dip saves your stalk from some contact erosion too.  

[unburntfuelinthemorning]

Probably the simplest would be to squeeze in some led stop/tail bulbs to replace the sidelights and use the stop part for the dimmed headlights with a crossover relay switched by the ignition.

 

For closer to the original you could use a PWM motor speed controller in place of the ballast resistor. Haven't tried it, but don't see why you couldn't just switch the dip in parallel on top of the dim as there'd be no voltage drop like the ballast resistor creates for dimming.

Volvo did that on their 240 but a conventional 21/5W bulb for front sidelights and running lights but they used a separate light unit with a dedicated lense to diffuse the light correctly.  I think a 21W bulb or LED equivalent in a 7" headlight could be a little dazzling without the correct diffusion of the light.

 

I had to look up PWM!  Found out it means pulse width modulation.  I thought this would just make the light flicker and reduce the life of the bulb but then found this discussion about just that although not for a car I don't think:  https://forum.allabo...en-bulb.102946/

 

I think the resistor method is nice and simple if a little crude; although the best way would have surely been to have a dedicated dim bulb with a reflector to suit, either within the headlight or separate, which came on when the sidelights and ignition were both on.

[Ethel]

You might be right about it being a dazzle-dip alternative. I'd hope it not being at the focus of the reflector would diffuse the light more, but an LED bulb is really multiple points much brighter than the 21 watts equivalence suggests.

 

Still, you could always add a resistor to dim it down a bit 

[unburntfuelinthemorning]

Did you work out what's what?

 

From the colours I'll guess:

 

2 & 8 one to the headlight dip beams, the other from the column stalk

 

4 is the supply via the ballast 

 

5 is the supply from light switch and it's basically a cross over relay to connect either 5 or 4 to the headlights

 

1 senses the ignition is on and 7 senses the sidelights, having both live will switch the relay to 4.

 

With whichever of 2 or 8 is from the stalk live the solenoid will default the other back to the normally closed terminal 5.

 

6 is the earth for the switching circuitry.

 

 

So it could be having dim dip saves your stalk from some contact erosion too.  

Nearly:

 

8 is from column stalk and 2 is to dipped headlights;

 

5 senses headlights on and not just sidelights and deactivates relay;

 

2 and either 4 or 8 carry the heavy current;

 

1, 5 and 7 are live at various times but the only combination which activates the relay and therefore activates dim headlights is when 1 and 7 are live and 5 is not live; any other combination deactivates the relay.

 

I think the blue wire feed to 5 is used so that when main beam is in use the dim dipped beam is switched off.  (Edit:  And also when full dipped beam is used otherwise the lights would remain dim)

 

It makes no difference to stalk contact erosion as the full current still goes through it - the relay is inserted into the white/red wire between the dip switch and the headlights.

 

I am planning to use another relay or two to take the heavy current away from the interior switches at some point.

Edited by unburntfuelinthemorning, 02 March 2019 - 07:14 PM.

[Ethel]

Makes sense, I'd overlooked  that you'd want to kill all dipped beam when on high beam.