Fitting a Battery Master Switch

[Jathro]

I'm just fitting a Battery Master Switch using the kit from CC.

 

I've disconnected the 2 Brown cables (+ 1 thin brown cable for the imobiliser(?)) from the +ve battery terminal and need to connect these to the very much thinner brown cable included in the kit.

 

Firstly, is it OK to use this much thinner cable to extend the 2 original cables to the switch, using the 1/2 inch ring terminal to connect to the switch, which seems more suitable for larger diameter cable??

 

If so, what is the best way to connect these all together - solder??

 

cheers

[Paul Deslandes]

How much thinner is the new cable? Older cars (mine's '95) had pretty heavy duty cables between the alternator, battery and ignition which were probably overkill. The new cable needs to be able to carry at least 30 Amps as it feeds all the electrics including the lights, battery charging etc.

 

The third, thin wire is almost certainly the alternator 'battery sense' cable which measures the battery voltage, originally at the battery, and feeds this back to the alternator regulator 'sense' terminal so it compensates for voltage drops along the cables. Ideally this wire needs to be connected to the master switch terminal although in practice it may not matter if you just bunch up the three wires, together with the new thinner brown one to the switch.

 

So long as the wire can carry the current without excessive voltage drop and doesn't get hot with everything on, it should be fine.

 

Edited to add that crimp and solder would be the best way to join them. ALternatively, if they all have ring terminals, you could put a nut and bolt through the lot with several layers of heat-shrink insulation over the top.

 

Edited by - Paul Deslandes on 21 Feb 2011 12:16:03

[Jathro]

Mine is a 95 also. The 2 original cables are both 5mm overall diameter (inc insulation). The supplied cable to extend to the switch is 3mm overall. It justn't seem right to me to extend these 2 with the single unless the originals were considerable overkill as you say.

 

ta

 

 

[Paul Deslandes]

Modern vehicle cable has much thinner insulation than of old. That's why its called 'thinwall' 😬 Its the cross sectional area of the copper that matters. Unless you want to get theoretical and measure the number of conductors and their csa to calculate the current carrying capacity, I should hope that CC will have rated the cable correctly and just use it. If it gets hot or the insulation melts, give 'em hell!

 

 

[Jathro]

Hopefully finishing it off tonight.

 

On the bright side, if the wire does get hot, I could remove the heater....

 

cheers

[Paul Deslandes]

true

[Jathro]

All finished apart from the tidying:

 

Did have a slight hiccup though, following the 7faq wiring, the switch has Z and W terminals:

7faq

The switch now has 1 and 2 terminals as below:

here

I assumed* that Z would equate to 1 as I followed the template also in the faq. You can tell when this is wrong as the car will turn over but not start, the smoke from the resistor is also a bit of a give away that something is amiss . Swapped these as per the second link and all OK.

Was I just being daft or would an adjustment to the faq be an option??

 

ta

 

*I know, never assume etc etc...