Alternator question..

[Sr20Tz3]

Hey guys bmw z3 in aus preparing for track use
Just wanted to run a few questions regarding alternator cut off disconect. How do you guys have your alternator wired up ? Ive heard you shouldnt run the alternator straight off the kill switch as it can damage the diodes?? Should i run the main power cable to energize through a relay?
Also the 2 other cables i think from memory one goes to ignition and the other is for the charging indicator?
Btw car is running aftermater ecu and race pak dash and no bmw modules All the original wiring has been removed.
Regards James

[CoMZ302]

James, when running an alternator (some don't) you'll need a kill switch that has two separate circuits (4 poles). Without those separate circuits, your alternator will continue to power your aftermarket ECU and the car won't turn off.

Here's a good diagram, that includes a resistor/shunt for the alternator:

https://www.pegasusautoracing.com/do...ocID=TECH00109

And if you don't have a 4-pole cutoff switch, I'd recommend: https://www.pegasusautoracing.com/pr...asp?RecID=1464

[darbyfam]

Concur with everything said above.

On the 4-pole cutoff switches, be careful as there are some inferior ones out there. Pay attention to the note Pegasus has on their switch:
Question: How do I know if I'm looking at the genuine article and not a lower quality clone?

Answer: The terminals of the genuine highest-quality switches are plated with a tin-alloy and are therefore silver colored. Lower quality clones have unplated brass terminals. In addition, genuine switches are shipped with half-height nuts while clones are usually furnished with full height nuts.

[Sr20Tz3]

Thanks guy good read. And the two other wires on the alternator just connect to hot on run and start?

[jimmypet]

After having two of the major "brand name" racey house 4 pole kill switches fail and one kill an alternator I did some searching and came up with a high current Cole Hersee 4 pole switch which has worked flawlessly since install.

Part number 75912BX

http://colehersee.com.au/product/dua...master-switch/

[exvitermini2]

My car is wired with a 2 pole switch. Main wire goes from battery to starter, jumper wire from starter to alternator, and a jumper wire off the starter into the cabin to the switch. Switch controls power to all electronics.

My battery is in the place of the stock ecu though, so there is no cable running front to rear.

[Sr20Tz3]

My car is wired with a 2 pole switch. Main wire goes from battery to starter, jumper wire from starter to alternator, and a jumper wire off the starter into the cabin to the switch. Switch controls power to all electronics.

My battery is in the place of the stock ecu though, so there is no cable running front to rear.

So essentially u have a live wire in the engine bay that you cant isolate incase of an emergency.

- - - Updated - - -

Thanks jimmy ill look into it .

[exvitermini2]

So essentially u have a live wire in the engine bay that you cant isolate incase of an emergency.

.

Correct, I prefer that over a live wire the full length of the car.

[Sr20Tz3]

Fair enough