Electrical Issue in main power cable of SpecE30- ideas?

[redrocket328]

The description is wrong. That is a three pole switch (six connections). The Bimmerworld description of the same switch (called a four pole) is also wrong. One pole is one contact in the switch which means one pair of contacts.

At the risk of being redundant, that is a bad location for the kill switch (see my earlier post and I have the pictures of the result to prove it).

Jim, thanks for the input. I do see the reasoning you have behind a better location that you have recommended. A lot of the car will be stripped down to go into paint and I will likely move everything then putting it back on. Thanks again.

[jlevie]

The description is wrong. That is a three pole switch (six connections). The Bimmerworld description of the same switch (called a four pole) is also wrong. One pole is one contact in the switch which means one pair of contacts.

At the risk of being redundant, that is a bad location for the kill switch (see my earlier post and I have the pictures of the result to prove it).

[redrocket328]

Can you post a link to your kill switch? I have never seen a proper battery disconnect that was 6 pole.

are you looking for a link to where I bought it or an actual picture of it installed?

http://www.turnermotorsport.com/p-1614-sparcoomp-battery-cut-off-switch-kill-switch.aspx

I picked up the sparco one from turner. Great product. I installed it in the 3rd hole for the windshield wipers that would be used for right side drivers cars.

[redrocket328]

After spending time with the car today, it came out to be a bad ground cable to the engine. I put a jumper from the battery(+) to the distributor block and still didnt start. Put a jumper from the battery (-) to the engine block and fired right up. At that point the only thing it could be was the ground strap on the engine. Replaced with one I had laying around from a parts car I had a while back. Starts up and runs great.

Jlevie, thanks for clarifying, but yes you are correct. My brain was fried at work when I posted originally. And yes it is used to properly ground the alternator and isolate the battery when the switch is used. I have seen other people use a standard 2 pole switch and run the alternator wire into the switch and just have the one main power cable running back to the battery. I dont know why they would do that since it doesnt properly ground the alternator and can cause some serious issues when used.

Thanks for the help guys.

[jlevie]

Jim, is that SpecE30 rules? PRO3 uses an old school battery kill, just a 600A single pole mounted on the back of the car.

The multi-pole kill switch is to satisfy general competition rules. A kill switch must be able to stop the engine as well as isolate the battery.

A single pole kill switch that simply disconnects the battery isn't guaranteed to stop the engine. Even though the battery is disconnected, the alternator can (and usually will) keep the DME operating and thus run the engine. You need at least a two pole switch to stop the engine with one of the poles interrupting power to the ignition coil or DME.

The third NC pole is just for protection of the car's electronics. When you disconnect the battery on a running engine the alternator can spike. With no battery to absorb the spike there is the possibility of damage to the electronics. The NC contacts connect to a resistor going to ground to absorb that spike.

[StereoInstaller1]

Jim, is that SpecE30 rules? PRO3 uses an old school battery kill, just a 600A single pole mounted on the back of the car.

[jlevie]

I think the OP means a kill switch with six connections (a three pole switch)

Any car with electronic fuel injection needs a 3 pole kill switch. That switch will have one pair of NO contacts for the main battery cable, one pair of NO contacts for DME power, and one pair of NC contacts for an alternator bleed to ground.

[StereoInstaller1]

Can you post a link to your kill switch? I have never seen a proper battery disconnect that was 6 pole.

[spdracrm3]

yes a voltage drop test will tell you exactly where there is above normal resistance in a circuit (ie bad connection,internally corroded wires). nice thing is you can go to every junction in the circuit and narrow it down to the exact location rather than guessing .

if you look a a diagram for example and a circuit has a connection at either end ie load (headlight) power source on other end (ie fuse ) and a switch in the middle you should not have over .3v drop in entire circuit (measuring between headlight and fuse ),no more than .1volt drop for every connection in a circuit is normal with circuit on(loaded) .so if in that circuit you had 4v on voltmeter you have a problem so you go between each junction till you find the one over .1v and theres your offending connection and you can now look closely at that part for problem

[redrocket328]

do you have a voltmeter ,if so load the system (ie a draw like all lights on)and voltage drop test the entire circuit (page 7 of every BMW ETM manual shows you how) downloadable here http://www.wedophones.com/BMWManualsLead.htm and it will tell you exactly where the problem is ,your right in thinking you have a corrosion/connection/resistance problem somewhere in the circuit so just need to know how to test for it and voltage drop test is it..... if your going to be racing and maintaining the car no time like the present to learn this diagnostic test as you will use it again and again

Thanks. I do have a volt meter. Usually just use to to check simple voltage inputs but im sure i can figure that out. My question is, what exactly would that test tell me? Would it just confirm that I have a resistance issue?

[jlevie]

What might cause this? the connections? Corrosion in the cable or connectors?

Solutions? Replace the entire cable? or replace the connections?

I am thinking that I am going to get a new O-ring connector and a universal battery terminal connector to throw in the ends up the cable without replacing the cable. Its always a possibility but im really doubting the actaully cable is bad. Or am I wrong?

To connect the cable to the kill switch you had to have terminated the cable in a ring terminal. That connection needs to be a solder joint, not a crimp. Unless the cable has been damaged, the battery connector (if clean and tight) shouldn't be a problem. But there could be a poor connection on the ground cable from the battery.

I realize that placing the kill switch on the cowl is popular because it is the easiest solution. But that is a bad location. A good hit on the right front corner can result in a short and fire. Also it doesn't take much damage to render the kill switch inaccessible. The best place to mount the kill switch is where the harness bar meets the main hoop. An alternative that is just as good is to mount the switch on the inside of the right front down tube. In either case that places the switch inside the cage and in easy reach of emergency personnel. That also means that the hot side of the switch is located entirely within the cage area and thus protected from damage.

In a like manner, it is best to move the battery to the trunk floor between the shock towers. In it's normal location it is in the crush zone and is at risk in an incident.

[AndrewBird]

Could be as simple as a bad ground at the battery. I would double check the connections at the battery before anything else.

[spdracrm3]

do you have a voltmeter ,if so load the system (ie a draw like all lights on)and voltage drop test the entire circuit (page 7 of every BMW ETM manual shows you how) downloadable here http://www.wedophones.com/BMWManualsLead.htm and it will tell you exactly where the problem is ,your right in thinking you have a corrosion/connection/resistance problem somewhere in the circuit so just need to know how to test for it and voltage drop test is it..... if your going to be racing and maintaining the car no time like the present to learn this diagnostic test as you will use it again and again

[redrocket328]

I see two possibilities. One would be a high resistance in the cable from the kill switch to the battery and the other would be a high resistance in the ground cable from the battery to the frame.

What might cause this? the connections? Corrosion in the cable or connectors?

Solutions? Replace the entire cable? or replace the connections?

I am thinking that I am going to get a new O-ring connector and a universal battery terminal connector to throw in the ends up the cable without replacing the cable. Its always a possibility but im really doubting the actaully cable is bad. Or am I wrong?

[jlevie]

I see two possibilities. One would be a high resistance in the cable from the kill switch to the battery and the other would be a high resistance in the ground cable from the battery to the frame.