Grounds connection for front headlight assy

(David Jauch) #41

And it was before. I like this though: ideally one would fuse right at the headlight switch, with a big fuse for ‘1’ and ‘4’ and another one at the relay, brown?
The headlight switch brown should probably not be fused because at least the sidelights should stay on for safety in case the big lights blow.
I don’t have spark noise for the dip stalk?

(Aristides Balanos) #42

That’s a good idea, one fuse before the headlight switch will actually protect the entire primary circuit.
5A will be OK as it will only feed the relay coils.
The secondary circuit will be protected either by the headlights fuses, or in your case by the relays built in fuses.

(tony) #43

hmm…hadnt even thought of the stalk switch…if the wiring and circuitry is separate,
a relay would be the only option under my regime, as “rare switch” protection is the name of the game on older vehicles…try getting a 420G stalk assembly…(or light switch), when you need one!

I think I can place the relays so they are not terribly visible, on the LH radiator closing panel, with a bunch of other relays. No need to run wire that is greatly thicker than needed.

probably run 15A fuses for highbeam

(Jochen Glöckner) #44

Wow, Aristides,

this is a lot more sophisticated than usual relay wiring patterns - I downloaded and saved it on the spot! Kudos! But seriously - even though my car is a generation older than yours and original in that respect (except for the light units), I can’t see any shortcomings with light output nor have I ever experienced sparks from the light or stalk switch.

Once I had a Ford with a 6 V power system. With a decent battery there should have been around 7.2 V at the lights - I measured 4.8 V instead and the light output - “Like a candle in the wind” - corresponded with that. Whenever I’m tempted to install relays today I first check voltage, and as long as there is full voltage at a testing light at the terminal, I’m happy to tell myself that a relay won’t bring much improvement.

The main switch is said to carry the load and in fact there are hardly any reports on this site of failed light switches. The stalk switches are different maybe, but still it doesn’t look like they get eaten up …



75 XJ6L 4.2 auto (UK spec)

(Jochen Glöckner) #45


so where did you put the fuses for the power circuits to the headlights? Still to the fuse box bracket?



75 XJ6L 4.2 auto (UK spec)

(David Jauch) #46

No, Jochen,

what I got was relays with integrated spade fuses. They look like regular relays, but have spade fuses on top. It’s all where the fuse box used to be on the SIII. Tight fit - If you want, I can take a picture of the whole installation tomorrow and you can tell me about your thoughts regarding my (coming up) TÜV inspection including historical plates. :slightly_smiling_face:

Best, David

I liked that!

This is the article. no affiliation, etc.

(Jochen Glöckner) #47

This is smart. I doubt that TÜV will complain about that - usually they say that historic plates are not affected by changes contributing to safety or eco-friendliness. Have you put the wires into a sleeve? I’d use 8 mm diameter and strap it cleanly - I bet no one will complain.

Good luck anyway


(Frank Andersen) #48

I forgot that the SI did not have the lights relay, Tony - so your concern is very relevant. Even though the light switch is dimensioned to take it…:slight_smile:

My concern was voltage loss, and additional relays, close to the headlights, will shorten the wires and reduce resistance. The light relay was introduced to ease the load on the light switch - which is fair enough. Then, some have added extra relays to reduce load on the light relay, which is sort of overkill.

Relays’ control current is very low - but the primary function of fuse is to protect the wiring, not the components. Only components that may cause excessive current if they fail, should be fused’. Which makes fuses necessary only for the ‘output’ connections on a relay…

I like belt and braces - but there is a limit, or it is ‘turtles all the way down’…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

(Doug Dwyer) #49

Yes, the headlight switch (unlike most of the other manually operated switches) is apparently quite robust. And it does carry the load, at least on the Series III cars.

It’s hard to argue with success. Adding the relays has been popular for years and everyone reports good results.

But, there’s more than one way to skin a cat. If someone is experiencing sub-par headlight performance it’s virtually assured to be a voltage drop situation and would be a simple matter to check voltage in a few spots along the path to see where the drop is occurring. Dirty bullet connectors would be very high on my suspect list…although I have to wonder about degraded contacts inside the switch, even if the switch hasn’t outright failed.

My concern would be adding higher-powered headlamps. I’d think that adding relays would be a must-do in that scenario…as the original wiring gauge appears to be ‘just enough’ to carry the load of standard lamps.


(David Jauch) #50

Compared to the e36 my lighting is phenomenal and nothing but phenomenal. It is okay compared to most cars, and adding relays has improved on that slightly, just by eliminating the three metres of wiring to the switch and back.
If contacts degrade then because of usage. What might help is putting in “brighter, bluer, whiter” lamps of the same wattage; they will probably get as bright as normal lamps with stronger wiring?

(Carl Hutchins, Jr. ) #51

Some points from one that barely navigates electrics.

  1. My SIII has two means of lighting the headlamps. The rotary switch on the fascial. That path includes the “famed” Hella relay box. But, the other is the stalk for selecting upper and lower beams or flashing… As indicated here, more delicate than the rotary.
    But, does it switch the full load or trigger the Hella? I could go out in the shop and look at the S57. naah, it’s cold and wet out there!!!

  2. Past lister, Alex Carnarra created a circuit to “aid the Hella”. I almost understood it.

  3. A couple of years ago, I replaced the original seal beams in my car. Fresh units with halogen a lot better. My son was concerned that I used more “powerful” lamps that would draw more and tax the old wires.
    Valid, I agreed. but no more Watts. Just fresh units.

  4. Tales from the past.

A. Circa 1950, school chum Roy decided to recreate his high school ride. A much refined 28 Fords coupe turned roaster. A cheap car lot denizen that was badly abused to a slick “A”. We found a similar one. Sixth bucks. Tattered and torn, but ran fairly well.
We did the prelim. chopped off the top and ditched the fenders. then went rabbit hunting at night in it. Ooops. got stuck in the sand. Roy gunned the engine, the after market sealed beams got very bright, then went dark!!! We got out and navigated home by flash light. The necropsy!! SOG, the PO used the hot post on the cut out for the generator as the source of 6v for the lights.
Seemingly Ok if rpm’s kept low!! but, not so, sans the battery as a dampener. Minor fix? Naah, Roy not pleased. A total rebuild followed.

B. Sort version of an adventure at a similar time. John and I decided to go in to a Christmas tree venture. Added high sides to our trailer. Hooked it to my venerable 37 Ford
off to the mountains or rural New Mexico. Made a questionable deal to cut trees. Worked hard all day, trailer loaded. Dark. Homeward bound. used 1st and 2nd, a lot. Not only for the hills but to get the R’s up and volts to the lamps to see by, OK, but, using far too much gas… No service stations in the back country…

Hw we got home, another tale for another day…


(David Jauch) #52

1: pulling the stalk grounds the hella and powers all six filaments (!) via the brown power to relay. This will fry it over time.
All light goes to the relay via blue from the switch, except for, when the rear fogs are selected, my car bypasses the relay and turns on low beam (which, together with some tape, saved me not that long ago when the blue to hella lost power). Bottom line: relays, yes. I recall, but don’t like the Cannara solution.

(tony) #53

with regard to the high beam flick switch, circled in blue

in regard to the above circuit

my thoughts are that a fused relay for each headlight,
placed at each junction circled in yellow, will protect the flick switch from supplying high current?

I could technically get away with 2 relays

am I missing something ?

the situation is fuses 1 & 2, circled in red, are in the dash fusebox, and the (short looking in the diagram) wire to the yellow junction is actually about 8ft long!

there is a short (18") twisted pair joined by bullets at each headlight

(David Jauch) #54

Tony, you can theoretically get away with a relay just after the blue flick switch if you want to protect only that.
For the full operation, yes, you can easily get away with two relays. I’d like to improve this circuit and at least put in two relays for the low beams. That will not only complicate troubleshooting but help you with driving home should a relay or its fuse fail.
The yellow connection is perfect to (maybe in a way that won’t need wires cut) splice in the relays and give the improvement in lighting. In that case four relays sounds very good.
That is, use the bullet connectors if you can and simply regard the relay as if it were the lamp (all you want is the relay ‘switched on’ for now. And then just add the power wire and route it to the lamp).

(Aristides Balanos) #55

No it will not, because once you put the relay its fuse will only protect the secondary circuit.
The primary circuit (relay coil and flick switch) will have no protection.
Caveat: I am assuming that the fuse in the relay is for the secondary circuit. if not then it’s the other way around.

Yes, but if you want all four headlights on high beam it’s a bit of a stretch, you will have +25 Amps.

The SIII has four fuses, one for each headlight in the engine compartment.
A more fail safe configuration.
As John says, the more you separate them, the less possible will be to find your self with out any lights at all.


(David Jauch) #56

I was thinking that the objective is to reduce current through the switchgear. Which will be achieved by making them only power the relays.
It is true (is it?) that there will be no fusing for the primary circuit, but also almost no load. Were there a short… we have fuses 1 and 2, no?
But in eliminating the voltage drop of the wiring and the high current through all switches we have all the improvement!
The SIII setup is also somehow complicated and I feel right at home with my four relays - left, right, outer high, inner high. Which is what I‘d do here, limiting current through switches, limiting voltage drop, adding the safety via more fuses and now what he should also do is change out the fuse in the panel to a small one that protects the switch.

So. Insert 4 relays that have a fuse each for the high power circuit. Insert them where the bullets connect. Change the existing fuses in the now low power circuit for 5A ones (or so). Done.
Maybe a big fuse for the main power to the relays, but i.e. the SIII is unfused in that regard and I just put a protective tube around the wire.

(Aristides Balanos) #57

You have two different circuits.
Where there a short you need to protect both.


(David Jauch) #58

The red fuses should protect the switch, and the yellow fuses will protect the lamp circuit or am I wrong here?

(Aristides Balanos) #59

They would indeed if they were fuses but from what I understand they are just junctions…

(David Jauch) #60

Red fuses 1&2 protect the switches, and the future relays at the junctions (yellow) will have a fuse each for the load circuit.