Headlight Upgrade for 86 XJ6 III

Certainly Frank,

I was assuming that there are 13.6+ V at the dynamo. Then a loss of more than 1V will affect light output at the headlights significantly.

Best

Jochen

75 XJ6L 4.2 auto (UK spec)

TO ALL … When I started this request for help I had no idea of the wealth of knowledge you guys had to offer ! Never have I been left in the dark (pun intended) as to how to replace the side marker lamps. All this stuff about headlamps is fantastic additional knowledge … I now know how to upgrade them !
Seriously, Many Thanks.
Cheers

Robert,
Would a relay with a higher amp rating help any? Or maybe just replacing your 30 year old relay with a new one?? Does Hella make a relay with a higher amp rating that would plug in?

No, and I doubt the relay is a weak spot voltage wise.

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Yes. But it’s not as simple as that. The Hella relay has a “memory.” This is so it can convert the momentary contact of what was originally just a “flash” contact on the steering column" to an alternating high-low-high-low etc. action when the flash contact is hit multiple times. This was to avoid putting an actual switch on the column to replace the floor switch used on earlier XJs. Within the Hella, a little plastic wheel rotates, like a ratchet and pawl, to alternately switch between high and low as each flasher pulse comes in. The relay contact controlled by this is marginal–the plastic wheel can melt. Upgraded (higher current) lights make it worse. Just enter “Hella Relay” into the XJ archives to see what I’m talking about.

If one “unloads” the Hella by letting it switch relays (which in turn switch the headlights) instead of lights it is more reliable, and there is less voltage drop. Plus, the Hella isn’t cheap–another important reason to preserve it. The simple relays needed are very cheap, and quite reliable. IMHO.

edit: to be clear…you don’t replace the Hella, you let it drive two additional relays downstream.

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And to add to Robert’s very correct remarks, adding a 1.8Ω 2W resistance to the Hella relay will preserve the stalk switch and reduce the arcing every time you switch from high to low beams.
I actually opted to drive it with an extra relay that eliminated the arcing completely.

Bellow is the schematic of my installation.
I used one 30A relay for both Low beams, but for the High beams I used two as I wanted to have all four headlights on. They are mounted at the fuse box bracket.

IMG_0095

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It is very important to have one fuse per side, so if one blows there’s still some light. The second picture didn’t load, nice installation!

Has anyone tried the lights from Daniel Stern? Pricey, but any brighter??
https://www.danielsternlighting.com/products/products.html

It’s the lightbulbs, and the Volts they get, that determines the brightness Roger.
The mirror reflects and the glass creates the pattern.
They might be of very quality but how good, or bad, can a bucket and a piece of glass be?

Aristides, et al,
I wasn’t aware the ‘Hella relay’ was more than just a relay.
I’ll just stick to using better bulbs and will plan on adding relays. Speaking of which, I had always thought a capacitor was needed to prevent arcing. After a little search it seems an RC network is best. Found this article which seems to explain it pretty well.
tinyurl.com/3ydat3s2

Not that I am about to do that. that idea was percolating in my brain. neat, that folks more skilled in electrickery see it as viable.

Relays have intrigued me for decades.

A few years ago, the FP relay in my lumpf fell from the rack on to the hot EGR pipe!!! It melted a hole in the case. The engine quit as well Came home, a really short distance on a flatbed!!! Easy diagnosis and fix.

Intriguing was the peek inside, the teeny coil and arm!!! .

Did not past lister Alex Carnara tout this piggy back relay concept.?

Carl

Good memory, Carl. He even published a schematic diagram. Problem with his design was that the extra relay was in parallel with the Hella. That doesn’t work at all. You can’t share the load between relays or switches–which ever closes or opens first gets the brunt of the current or arc. You have to let the Hella supply the coil of the extra relay, then let that relay supply the load. A “daisy chain.”

Aha!! That may well be why I did not get it!! Now, with your explanation, I do!

Thanks.

Carl

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Indeed, Robert - but the relay providing lamp power will still arc; the more power the in the arc. Which does burn the contacts as it does on the mechanical contact breaker system - where the capacitor has a double function.

The breaker points operates 1300 times a minute at cruising speed (twice that on the V12) - the light relay…hm…less. Admittedly, the Hella carries much higher current, but is also dimensioned accordingly - but burnt contacts is not a coomon Hella malfunction. The main loss to the lights is the resistance of the rather thin wires originally used, and bad connections. Doubling the wires is just as effective, and simpler, as relays to eliminate this loss - but the arguments continue…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

Absolutely correct - the main failure mode of the hella is melting. Voltage loss, not so much.

… and the stalk switch contacts getting fried.

Aristides,
What gauge wire should be used?

The thicker the better really, less resistance. That’s where the idea of one fat wire to the relays in front comes from.

After my fuse box got too unreliable I did what Aristides did, just without the fuse box (I did away with it and the fan got an inline fuse - there was no way I could repair the fuse box).

I used relays with integral blade fuses.

**
The stalk switch (awfully thin wires) only grounds the relay coil, Aristides - so little current is passing it, unless the relay coil is shorted?

Frank
xj6 85 Sov Europe (UK/NZ)