Headlights and voltage drop

[Mike R]

Dear all,

I've always thought my headlights were a little dim, but always thought it was just a Triumph thing!

I've considered for sometime whether to go for the halogen upgrade you can get and finally bit the bullet and purchased a pair of headlamp units with standard wattage halogen bulbs.

 

Whilst doing this job thought I'd rewire through fused relays to reduce the fire risk - and yes I did once have a dash fire where the wiring shorted - not a good experience.

 

Thought i'd measure what voltage drop I currently had and was stunned at the result.

 

The wire goes ...

Battery to solenoid to dash switch to column switch to headlight.

 

I dropped the headlight out of its position to get to the connector on the back, switched it on and measured the voltage going in.

The result was 0.9V with 12.3V at the battery.

I.e. around 11v drop over the wiring and switches.

So, to test I ran a wire direct from battery to headlamp. The brightness increased markedly and the voltage was over 11V proving the voltage drop issue.

 

So, the questions ....

 

Is such a drop "normal" for triumph (GT6 mk3)?

Also, i followed the earth back into the loom, but difficult to tell where it goes from the point where the 2 headlamps wiring joins. Does anyone know where the earth runs? I noticed there are 4 earths connected to an earthing point on the right of the battery tray - I guess this may be it, but wondered if anyone knew?

[rogerguzzi]

Dear all,

I've always thought my headlights were a little dim, but always thought it was just a Triumph thing!

I've considered for sometime whether to go for the halogen upgrade you can get and finally bit the bullet and purchased a pair of headlamp units with standard wattage halogen bulbs.

 

Whilst doing this job thought I'd rewire through fused relays to reduce the fire risk - and yes I did once have a dash fire where the wiring shorted - not a good experience.

 

Thought i'd measure what voltage drop I currently had and was stunned at the result.

 

The wire goes ...

Battery to solenoid to dash switch to column switch to headlight.

 

I dropped the headlight out of its position to get to the connector on the back, switched it on and measured the voltage going in.

The result was 0.9V with 12.3V at the battery.

I.e. around 11v drop over the wiring and switches.

So, to test I ran a wire direct from battery to headlamp. The brightness increased markedly and the voltage was over 11V proving the voltage drop issue.

 

So, the questions ....

 

Is such a drop "normal" for triumph (GT6 mk3)?

Also, i followed the earth back into the loom, but difficult to tell where it goes from the point where the 2 headlamps wiring joins. Does anyone know where the earth runs? I noticed there are 4 earths connected to an earthing point on the right of the battery tray - I guess this may be it, but wondered if anyone knew?

Hello

        The best thing to do is fit a pair of relays and heavier gauge cable.

Then you get brighter light an less strain on the light switch and dip switch

There are lots of circuit drawings on hear and esle where.

Roger

ps and a pair of Osram night breakers improve things even more

[dougbgt6]

Yes a voltage is drop not uncommon although yours is impressive! The culprit is quite often the dashboard switch, it carries ALL the current for the headlights, unfused!  Because of this it gets corroded and resistive and hot and sometimes catches fire.

 

Relays are the answer, I bought this wiring loom from China, ridiculously cheap, I was suspicious but I thought, worth a punt. In the event it's robust and works.

 

http://www.ebay.co.uk/itm/H4-H4-Headlight-Headlamp-Black-Booster-Wire-Harness-Cable-SAYG-AI3G-/152016433561?hash=item2364e2b199

 

 It does need modification, battery supply wire extended and headlamp connectors taken off and put back once the cables are inside the headlamp cowls. The earths screw directly to the chassis.

[Mike R]

Much appreciated - yes bigger cables plus relays and fuses is the way forward for me ... But of course the same current goes through the earth wire, hence the question where does the earth terminate?

 

Anyone know?

[dougbgt6]

Before and after the relay upgrade my headlamp earths screw to the chassis near the headlamp cowl. The battery negative clamps to the body tub near the battery and the body tub is bolted to the chassis. My car is a late 73 so it may be different on yours?

[Pete Lewis]

on the  the old Vit6 we encountered the 10v glow worms many years back,  I have always said getting 12-14 v at the pointed end makes the old filiament work wonders,  adding relays is the only way forward , adding halogen or nightbreaker is another step forward

I have just changed the 2000 Mk2 to crystal lense lamps  ,  and wow  they also look pretty mean

  still have the relays to fit but the suns out , and mowers in the shed 

Pete

[mishmosh]

would someone post a simplistic diagram of how to fit relays  please. 

[AidanT]

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjRw-Wx1MzMAhXGOxQKHaPLDXcQjRwIBw&url=http%3A%2F%2Fwilliamcolumbine.blogspot.com%2F2010%2F09%2Fheadlight-relays.html&psig=AFQjCNHgv1OdnjWINLbqrahEtcRClbE7AQ&ust=1462871011997648

 

 

This is the simplest I can find and will be using it for my conversion with Crystal Halogen units in the next month

 

I will refer to the manual wiring diagram for the switch side wires

 

Aidan

[AidanT]

BTW, anyone any thoughts on Xenon vs Halogen?

 

Thx

 

Aidan

[s.leah]

If you are earthing to the bonnet, it may be worth checking continuity between the bonnet and the chassis/battery -ve.

For a belt'n'braces approach, you could run a hefty earth cable from the earth point on the bonnet back to the central earth point on the car chassis, or even direct to the battery.

[Pete Lewis]

with all the rusty body tub connections we earth bonded all three body sections together and to the chassis then  back to the battery .

 

so yes belt and braces works

 

Pete 

[mishmosh]

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjRw-Wx1MzMAhXGOxQKHaPLDXcQjRwIBw&url=http%3A%2F%2Fwilliamcolumbine.blogspot.com%2F2010%2F09%2Fheadlight-relays.html&psig=AFQjCNHgv1OdnjWINLbqrahEtcRClbE7AQ&ust=1462871011997648

 

 

This is the simplest I can find and will be using it for my conversion with Crystal Halogen units in the next month

 

I will refer to the manual wiring diagram for the switch side wires

 

Aidan

so you leave the live feeds to the switch in place  But add a live feed direct from the battery feed ? 

[AidanT]

Hi

Yes leave the switch wiring in place and use it to energise the solenoid switch. A thick cable from the power source (fused) from the battery (I'm taking mine direct from the alternator) to the solenoid then wire the the switched side to the lights

 

 

Aidan