Installing a kill switch on an E36 - questions

**jamanta** · 11-25-2016, 07:59 PM

Hello,

I have a 92 325is (M50) that I'm building to race in Chump Car and Lucky Dog Racing in the Pacific Northwest. A kill switch is needed as part of the rules and in tech the car is revved up to about 2k and the switch needs to cut all power. The whole car needs to be shutoff, meaning that even the DME needs to have the power cut.

I have bought a 2 pole switch and I have seen in some posts that either a 4 or 6 poles are needed. I have searched all over and haven't really found a definite answer. Looking for your help here. Here's what I'm thinking, please correct me if I'm not right.

What I see:
- There are two cables running from the battery all the way through the car, firewall and into the jump start "hub". From there, the wires go everywhere in the engine bay.
- Looking at the alternator, there is a red wire coming out of it and runs to the starter. It is bridged there and another wire goes back to the jump start "hub".

What I'm thinking:
- Run the thick battery cable only to the switch on the dashboard.
- From the switch on, run both the thick and the thin cables.
- Instead of bridging the wire from the alternator to the starter, I would splice that wire and connect all the way back to the battery so that the alternator has a place to send its power after I hit the kill switch

Again, I haven't seen a definite answer on this. Looking for your guys' input. Thanks!

**jamanta** · 11-27-2016, 03:21 PM

Bump. Anyone?

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**darbyfam** · 11-27-2016, 06:29 PM

I honestly don't know the direct answer on how to use the two pole. I know the six pole I use basically grounds the power to prevent alternator damage.

**cemmett** · 11-28-2016, 01:46 PM

I would use a cutoff solenoid kit (They can be spendy though; $120 +) to do it the correct way. Otherwise, you could use the two-pole as in the diagram here and just splice it into the middle of the cable running through the cabin, with a pull-down resistor to the negative terminal.

http://www.darren-criss.org/bmw-z3-w...076126c9f.html

**hoki06** · 11-28-2016, 10:01 PM

Here's my write up

http://www.bimmerforums.com/forum/sh...1#post29113971

**jamanta** · 11-28-2016, 10:23 PM

Originally Posted by hoki06

Here's my write up

http://www.bimmerforums.com/forum/sh...1#post29113971

Thanks! Looks like a 6 pole is needed. Your write up makes sense but I have a few questions.

- Did your setup completely cutoff the whole car? I can't have any power past the switch.

- Where did you attach your ground? Did you use one of the ground nuts either underneath the dash or the footwell?

- Is the resistor spliced somewhere along the the ground wire?

- Lastly, I want to save some $ so I will not buy the kit from Hard. What is the spec on the resistor?

Thanks a lot!

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**cemmett** · 11-29-2016, 12:44 AM

Originally Posted by jamanta

Thanks! Looks like a 6 pole is needed. Your write up makes sense but I have a few questions.

- Did your setup completely cutoff the whole car? I can't have any power past the switch.

- Where did you attach your ground? Did you use one of the ground nuts either underneath the dash or the footwell?

- Is the resistor spliced somewhere along the the ground wire?

- Lastly, I want to save some $ so I will not buy the kit from Hard. What is the spec on the resistor?

Thanks a lot!

Sent from my iPhone using Tapatalk

Agreed, the 6 pole is the correct and best method. I can probably answer a few of these questions.

1. Setup will completely cut off the entire car.
2. For grounds, use the ground nuts under the dash. I used those for my ignition switches.
3. Resistor should be spliced inline and heatshrunk, but you could get away with this: http://www.dimecitycycles.com/10-wat...onnectors.html
4. Resistor is 3 watt 11 ohm

**hoki06** · 11-29-2016, 07:17 AM

Originally Posted by jamanta

Thanks! Looks like a 6 pole is needed. Your write up makes sense but I have a few questions.

- Did your setup completely cutoff the whole car? I can't have any power past the switch.

- Where did you attach your ground? Did you use one of the ground nuts either underneath the dash or the footwell?

- Is the resistor spliced somewhere along the the ground wire?

- Lastly, I want to save some $ so I will not buy the kit from Hard. What is the spec on the resistor?

Thanks a lot!

Sent from my iPhone using Tapatalk

1. Yes, it killed the car every time. The true test is to rev the car to 1500-2000 and then kill it.
2. Pick any of the major body grounds. There are a several all over the car, pick the closest.
3. Yes, the resistor is spliced and heat shrunk in the ground wire.
4. Resistor spec comes from the 6 pole kill switch instructions (3 ohm 11 watt) http://www.ogracing.com/images/sparc...stallation.jpg

**jamanta** · 11-29-2016, 11:44 AM

Thank you guys!

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**Franky goes** · 12-18-2016, 05:28 PM

Here is my setup.
Been running well for the last 5 years.
http://www.bimmerforums.com/forum/sh...ghlight=switch

**Zxc4** · 07-25-2017, 05:43 PM

Can you guys clarify how the resistor is spliced inline? Are you separating the ground wire and using a butt clamp on the resister legs or soldering straight to the ground wire? Seems like the resistor legs are a harder metal and the butt clamp may not be effective. A picture here would be much appreciated.

Also, per Hoki's write-up/picture, is the power loop and ground wires (green in pic) a smaller gauge than the 10ga wire that comes from the battery (smaller red)?

**gavronm** · 08-01-2017, 01:42 PM

I soldered mine in and yes the power loop and ground wires can be smaller. I think I ended up with 12 or 14ga. Go with 12 if you're worried about it.

**frank9** · 08-09-2021, 03:14 PM

I have 2012 BMW 528i Xdrive for my son to take to the college, think about install a fuel pump kill switch, I just installed one for my other son, his 2013 Hyundai sonata got stolen, recovered with $6500 damage, I am assume the ideal is the same, the fuel pump are all at back seat close to the gasoline trunk, my question to you is did you installed on your bmw? did you cut one wire with what color? is that green with what color wire?

Thanks

Frank

Originally Posted by jamanta

Hello,

I have a 92 325is (M50) that I'm building to race in Chump Car and Lucky Dog Racing in the Pacific Northwest. A kill switch is needed as part of the rules and in tech the car is revved up to about 2k and the switch needs to cut all power. The whole car needs to be shutoff, meaning that even the DME needs to have the power cut.

I have bought a 2 pole switch and I have seen in some posts that either a 4 or 6 poles are needed. I have searched all over and haven't really found a definite answer. Looking for your help here. Here's what I'm thinking, please correct me if I'm not right.

What I see:
- There are two cables running from the battery all the way through the car, firewall and into the jump start "hub". From there, the wires go everywhere in the engine bay.
- Looking at the alternator, there is a red wire coming out of it and runs to the starter. It is bridged there and another wire goes back to the jump start "hub".

What I'm thinking:
- Run the thick battery cable only to the switch on the dashboard.
- From the switch on, run both the thick and the thin cables.
- Instead of bridging the wire from the alternator to the starter, I would splice that wire and connect all the way back to the battery so that the alternator has a place to send its power after I hit the kill switch

Again, I haven't seen a definite answer on this. Looking for your guys' input. Thanks!