8 replies to this topic

[Geofff]

I'm planning to fit new headlights into our 93 Sprite but I am getting hung up by cable sizing.

I have read all the posts by KernowCooper but I'm still unsure.

As far as I can tell the original headlights were 45/40 watts. I plan to fit 60/55 watt H4.

The blue/white cable to the main beam measures 2.5mm over the insulation.

KernowCooper rates the Amp draw on the new lights at just under 10 amps.

The question is should I rewire the headlights back to source with new cable as 2.0mm2 is recommended for headlights..or 1.0mm2..or will the wiring already in the car be sufficient amp rating?

I much prefer nuts and bolts to volts and amps.

thanks

 

[KTS]

as long as the existing wiring is serviceable, it should be adequate

 

a relatively straightforward improvement to the headlight wiring, that doesn't require completely rewiring the whole circuit, is to use the existing main and dipped beam feeds (blue/white and blue/red respectively) as triggers to relays that provide the power direct to the headlights from the main battery feed

 

you can buy pre-built harnesses to allow you to do this with relative ease - Wired by Wilson is one supplier  

[Geofff]

Now that is very useful. Many thanks for the reply.

I like the idea of going via a relay. I will contact Wired by Wilson.

Again many thanks

[andyapanel]

I second that recommendation for Wired By Wilson. Top notch work.

[cal844]

Third here for Wired by Wilson, I've had a radio head unit power lead fitted for 8 years, been faultless

[smurfomatic]

Wired by Wilson is great, produced a modified loom for me and was a great help throughout the process.

[Spider]

You'll find it very worthwhile replacing the wiring with something a little bigger than what they factory provide and adding relays.

The problem with the factory stuff is while it can - just - handle the load OK, there's a lot of losses along the way because it's smaller wire (put in more technical terms, the smaller wire has a higher resistance) and to further compound this, the total length of wire, from the solenoid (where it picks up the power from), through to the Headlight Switch and then up the column to the Dipper Switch, before heading out to the Headlights is quite a few metres of cable, adding more losses (resistance) along the way. These losses cause there for to be less voltage to the lamp. just a drop of 5% in voltage reduces the lamp brightness by more than 15% and a 10% drop in voltage reduces light output by 33% - 1/3 !  It's easy to see how much you loose by switching on the headlights, measuring the voltage at the starter solenoid and then again at the headlight terminals - I think you'd be surprised.

Fitting the next size up cable and relays in the engine bay, you'd be surprised how much brighter the standard headlights would be, but all the same, I wouldn't discourage you from upgrading to H4s.

[IronmanG]

Another positive vote for David at W by W

[Geofff]

Thank you for all the comments.

I'm going for the larger cable and a relay by W W. Wired by Wilson have solved another consideration and that is wiring in 2 spot lights.

Spot lights are a must have.

I have noticed that W by W do a harness that incorporates both headlights and spot lights.

Issue solved so very many thanks to you all.