Rating?

Post by **Peetee** » Mon Sep 10, 2007 7:00 pm

I want to order some wiring for Albert but I need to know what rating is appropriate for the headlights and indicators? The thing is the classic wiring company i have just looked at has a limited supply of colour codes for 17A cable and far more for 8.75A.

Post by **MoggyTech** » Mon Sep 10, 2007 7:30 pm

8.75 amp will be fine for the indicators and headlights.
Current (A) = Watts (W)/Volts (V)

Example 2x21W Indicator bulbs totals 42Watts/12V = 3.5 Amps
2X 55W Headlights = 120W Total / 12V = 10 Amps

Post by **Peetee** » Mon Sep 10, 2007 8:12 pm

Cheers matey!

Post by **jtd.75** » Mon Sep 10, 2007 8:31 pm

ohms law I hear you say and no not sherlock

Post by **bmcecosse** » Mon Sep 10, 2007 9:19 pm

So - from that example above - the 8.5 amp cable is NOT suitable for supplying the headlamps, where the single wire supply normally runs down to the front of the car and then splits to each lamp. You MUST use the heavier 17 amp cable at least up to the split point. Too small cable causes voltage drop (= dim lights) and can of course overheat and eventually perhaps catch fire!

Post by **MoggyTech** » Tue Sep 11, 2007 12:38 am

Ooops, yes indeed. For the main headlight feed before it splits to individual lamps, use 17 amp cable. Sorry folks my bad.

Post by **Peetee** » Tue Sep 11, 2007 6:25 am

It's OK BMC, I only need to make up the individual looms that go from the engine bay to each lamp.

Post by **Alec** » Tue Sep 11, 2007 7:54 am

Hello all,

better to have too large a cable than too small, but ensure that the connectors used are also suited to the cable size.

Jtd75, slight correction, that is not ohm's law (V=I x R) but the basic formula for D.C. power.

Alec

Post by **Peetee** » Tue Sep 11, 2007 4:45 pm

better to have too large a cable than too small

But that's the problem you see. I can't find the correct colour wire in the larger size so I was checking the smaller was up to the job.

Post by **Alec** » Tue Sep 11, 2007 5:40 pm

Hello Peetee,

you could try:- http://www.vehicle-wiring-products.eu/V ... mepage.php

they have the blue\white and blue\red in 17.5 amp size.
Of course you can run two wires of a smaller size together and connect them in a common terminal, untidy, but perfectly sound practice.

Alec

Post by **Peetee** » Tue Sep 11, 2007 8:20 pm

those were the people I tried and it was the green/red and the blue/white I couldn't find.

Post by **Alec** » Tue Sep 11, 2007 8:40 pm

Hello Peetee,

you need to look at the thin wall cable for blue\white, but you shouldn't need 17.5 amp for green\red which, if my memory is correct is an indicator feed?

Alec

Post by **jtd.75** » Tue Sep 11, 2007 11:38 pm

Hi Alec I know its not true but you and I know what he means

I was just trying to point out about the various formulars. Its not as easy as just plugging something in and hope it works

Post by **forbesg** » Wed Sep 12, 2007 1:52 am

Peetee wrote:
better to have too large a cable than too small
But that's the problem you see. I can't find the correct colour wire in the larger size so I was checking the smaller was up to the job.

If originality isn't an issue you could try doubling up on smaller wiring, just make sure you have the same amount of wire cross section.

-GRant F.