Re-wiring question

[andyborris]

I'm trying to re-wire my Triumph 2000 saloon.

It has six 6 watt bulbs in the sidelight circuit, which I calculate to consume 3 amps in total.

So I've used 0.5mm thinwall cable, (rated at 10 amps) for this circuit.

I've installed this circuit like a “ring main” with spurs to the lights.

All seems good, except I'm getting a voltage drop of about 0.27 Volts over the loom from the switch to the furthest rear sidelight, there are 6 bulbs in total on this section of the sidelight circuit, the front lights aren't connected yet.

All the lights use the bodywork as an earth return.

Is this an acceptable voltage drop? One sidelight seems dimmer than the other, but it's the bulb nearest the switch and 12V feed, so not the one I'd expect to see less voltage?!

I'm sorry if my question is long winded, I'm learning as I re-wire! And I've only connected the wrong light to the wrong wire once......still lots of wiring to do though!

[ferny]

I'm not an auto electrician but as far as I'm concerned that's fine. I get the same drop with my headlights after rewiring them and fitting relays. It's such a small drop you won't notice it. And it's also far better than the 2v drop another car was getting after an engineer for a large car manufacturer fitted relays! Ten minutes with an soldering iron cured that one.

For the dim bulb, have you cleaned the lens and reflector?

[optimusprime]

Be aware of using 'cheap' bulbs as well ......

[andyborris]

Thanks

To be honest and now I've had a look in the dark, it's a very, very small difference and I'm probably overreacting!

Or it may just be down to the bulbs themselves, the voltage drop is without any charge going into the battery, it's just a battery with test leads to check circuits.

What I'm actually finding hard, is working out the best way to route everything, I've decided not to follow Triumph and just use 4 fuses for everything.

I think having every circuit on it's own fuse is safer and makes it easier for me to trace any faults I make!

[SamR380]

0.27 volts doesn't sound too bad. Are you earthing to the body through the light fitting? Just need to make sure there's good contact. The difference could just be in the bulbs, as mentioned.

Sounds like you know what you're doing though. Yes, more fuses is better! It just makes looms more complicated and expensive for the manufacturer.

[benjy_b]

Using this calculator, your voltage drop is pretty much bang on

[andyborris]

Jan 5, 2015 22:56:50 GMT SamR380 said:

Sounds like you know what you're doing though

Kind words, but unfortunately   .....and that link is great. Thanks.

[andyborris]

Just used 100 meters of the cable......and about 2/3 done!

[DavidB]

On my Starion, with heater on full blast, lights on full and engine going, I get a drop of about 1v. Bulbs seem to use a lot of current.

[yoeddynz]

I've found that there certainly can be quite a difference in brightness between different brands of bulbs so try making sure they are all the same .

I love re-wiring cars. So satisfying especially if you have the time to do it neatly. Hannah is about to embark on a full resto of her mk1 triumph wagon and at some point it will need some new wiring.

[andyborris]

Jan 8, 2015 9:19:06 GMT yoeddynz said:

I love re-wiring cars. So satisfying especially if you have the time to do it neatly.

Any tips?

And wish Hannah good luck with her MK1, I'm also doing some re-engineering of mine, boiled the engine in Paris this summer when the rad fan failed to work.

So, I'm fitting a new (to me!) engine, still a 2.5 BMW M52 and I hope to get a radiator built that provides more cooling and allows me to fit a larger “puller” fan.

I've found that aluminium rads don't cool as well as the copper ones, so the BMW one (ally and plastic) will be ditched in favour of one more like the Triumph version.

But because I haven't got the space between the engine and front panel to fit a normal Triumph rad, I'm going to have one that mounts with core going into the nose cone, the reverse of how it is at the moment.

I'll also lose the rad filler and have it made crossflow style, hopefully this will provide plenty of cooling! And hopefully, I'll be able to change the thermostat, pump and fan without removing the rad too.

Luckily the head gasket didn't fail till a few weeks after I provided groom and best man transport for Colin Radford.

[robbert]

Have you wired them in series or parallel?

en.wikipedia.org/wiki/Series_and_parallel_circuits

[Battles]

Obvious question: have you swapped the bulbs over to see if the bulb stays dim at the same side or if the dimmer side changes when you move the bulb?