Headlight dip switch

[englishmaninwales]

Auto-electrics generally makes me feel anxious, especially in a 50+ year old plastic Lotus. But over the last few days I’ve learnt a bit, following my encounter with a smoldering headlight beam dip switch.
So what did I learn?
My early 1966 Elan S3 Coupe has S2 wiring, with bits added on (eg electric windows).
The S2 headlight wiring design is horrid, with the beam dip switch downstream of the (single) headlight relay, so the switch carries the full headlight (dipped or full) amperage. This would explain the ‘cooked’ appearance and smell of the switch, innards and contacts.
I was pleased to see the later S3 wiring diragram shows separate main and dipped relays, with the dip switch upstream of the relays.
The Triumph sourced headlight dip switch has the redundant third position blocked off by a piece of wood. Please tell me this was a standard Lotus factory modification, I love it. Practical, effective and cheap, if somewhat Heath Robinson!

Malcolm

[1owner69Elan]

The Triumph sourced headlight dip switch has the redundant third position blocked off by a piece of wood. Please tell me this was a standard Lotus factory modification, I love it. Practical, effective and cheap, if somewhat Heath Robinson!

Malcolm

The piece of wood in the switch was as delivered from the factory on my 1969 S4. I too was amused to find this.

[Verve]

I don`t know about the piece of wood ... but I concur that the early S3 Wiring Loom is an absolute Hazard !

I have communicated at length with Autosparks to make their replacement S3 Looms as per the later S3 " Workshop Manual " safer version ... but they seem reluctant to do so unless somebody gives them a loom to copy !

Fortunately , I removed the "singed" single Headlight Relay (under the dash ) in my Elan S3`s new loom (fitted by a PO ) just in time .... then I put a new main feed to new Headlamp Relays in the nose , whilst utilising the existing Dip Switch supplies out to just "switch" the new relays & not directly carry full current to the lamps as before !

A relatively easy fix , after a lot of "head scratching" as to why do the S3 looms not match the Workshop Manual !

I would highly recommend all S3 owners to check their looms a.s.a.p. ... particularly that single relay & wiring under the dash feeding the headlamp dip switch !

Paul .

[Mazzini]

The Triumph sourced headlight dip switch has the redundant third position blocked off by a piece of wood. Please tell me this was a standard Lotus factory modification, I love it. Practical, effective and cheap, if somewhat Heath Robinson!

Malcolm

The piece of wood in the switch was as delivered from the factory on my 1969 S4. I too was amused to find this.

The wood was also present on my S3.

[englishmaninwales]

I don`t know about the piece of wood ... but I concur that the early S3 Wiring Loom is an absolute Hazard !

I have communicated at length with Autosparks to make their replacement S3 Looms as per the later S3 " Workshop Manual " safer version ... but they seem reluctant to do so unless somebody gives them a loom to copy !

Fortunately , I removed the "singed" single Headlight Relay (under the dash ) in my Elan S3`s new loom (fitted by a PO ) just in time .... then I put a new main feed to new Headlamp Relays in the nose , whilst utilising the existing Dip Switch supplies out to just "switch" the new relays & not directly carry full current to the lamps as before !

A relatively easy fix , after a lot of "head scratching" as to why do the S3 looms not match the Workshop Manual !

I would highly recommend all S3 owners to check their looms a.s.a.p. ... particularly that single relay & wiring under the dash feeding the headlamp dip switch !

Paul .

Thanks for the advice and confirming my reservations about the S2/early S3 wiring design, Paul. Unfortunately that sort of electrical work is beyond my competence.

The headlight wiring and single relay appear all appear in good condition, it is the dip switch itself that has failed. There is evidence of previous repairs to the switch and arcing at the contacts, along with signs of excessive heat to the plastic switch core.

Maybe I’ll fit a replacement switch for now, keeping a close eye on the switch and headlamp wiring condition and performance.

I’ll look into finding an auto electrician who would do the conversion you describe to the later S3 headlamp wiring with twin relays.

Anybody got any recommendations for the N Wales/Shropshire/Cheshire/Wirral areas?

Malcolm

[TBG]

Just a thought. To reduce the current going through switches and so on fit LED bulbs..................D

[englishmaninwales]

Any idea on the current draw through the dip switch on original full beam v. LEDs?

[TBG]

Nope!!

Just googled.................How many Amps does a 100 watt LED light bulb draw?
A 100 Watts bulb draws 0.90 Amps.

Each 55-watt bulb run at 12 volts and draws 4.58 amps. These bulbs typically provide about 4,000 candela -- a measurement of light intensity. So 9.16 amps.

[Donels]

There are recent threads on converting to LED dipped/mains and its not straight forwards and a potential MOT failure.

[TBG]

It is actually very straight forward. D

[andyelan]

Hi
I think what Donels is eluding to is the fact that you're not allowed to fit a LED or HID in a headlamp assembly designed for filament bulbs.
Andy

[HCA]

Nope!!

Just googled.................How many Amps does a 100 watt LED light bulb draw?
A 100 Watts bulb draws 0.90 Amps.

Each 55-watt bulb run at 12 volts and draws 4.58 amps. These bulbs typically provide about 4,000 candela -- a measurement of light intensity. So 9.16 amps.

Again, Google is wrong, a 100W device on 12V draws 100/12 = 8.3A. What they might be trying to say is that an LED equivalent to a traditional 100W bulb is maybe 10W. A 10W device (eg LED bulb) on 12V draws 0.83A.

[englishmaninwales]

Ok, so a LED bulb conversion would be an improved, safe option for longevity of the dip switch and associated wiring in an S2/early S3 wiring loom, but is a non starter as this is not compatible with UK MOT:

“Existing halogen headlamp units on vehicles first used on or after 1 April 1986 must not be converted to be used with high intensity discharge (HID) or light emitting diode (LED) bulbs. If such a conversion has been done, you must fail the headlamp for light source and lamp not compatible.”

[ericbushby]

I thought it was OK to convert to LED Headlamps if the car was built before April 1st 1986. That ruling appears to apply only to later cars. Does anybody know the correct ruling. The LED suppliers seem quite confident in their products.
Also it may be that it only applies if replacing a halogen lamp, not a tungsten filament type like ours.
Eric in Burnley
1967 S3SE DHC

[Andy8421]

Nope!!

Each 55-watt bulb run at 12 volts and draws 4.58 amps. These bulbs typically provide about 4,000 candela -- a measurement of light intensity. So 9.16 amps.

A car battery with the engine running will float at 13.6V. I believe that car bulbs produce their rated output at 13.6V - even if the packet says 12V. So in your example, at 13.6V each bulb would only need 4 amps for 55W.

I have never seen a definitive source to confirm this though.