car kill toggle switch

linux44 · Sep 29, 2011

Hi Guys,
I am planning to install a kill switch on my car on the starter however I am not very good with electronics and ... , I have done an extensive research and here is where i am at :

1. I understand that my starter motor probably would want a high amper such as 70amp or so.
2. the starter can not be directky wired as if this was to happen a huge and think wire should have been wired form the starter barrel to the starter thus a thinner, smaller size cable is wired to a relay . the relay is then directly connectd to the starter using a high current cable. when i start the car the relay is switched on by the thin cable and thus current flows through the starter thick cable and hence engine start.

3.if i am to install a switch , i can do it by cutting the wire on the ignition barrel and connect each side of it to one side of the key and then the key will disconnect or connect them. My understanding is that i do not need a relay in here again as the amp should be low and acceptable,

4. my problem now is to find the right cable for my case for which i need to find the amp or the current that goes through the cable. from my understanding one way of doing this is by disconnecting the ignition wire on the barrel and then connect each side of it to my multimeter and then turn the starter key whereby i should see the amp flowing throught it . my understanding is that the positive lead should be on the output wire .
I have also heared that if the current is more than my multimeter amp power, i can fry my multimeter. mine has a rating of 10 A, does that mean i can do the test?

5. do u think i need a fuse or ... ?
I appreciate any answers from all memebers

MarkieSparkie · Oct 1, 2011

Hi Linux, Take a look at the following website, it may help.
Electrical System

MarkieSparkie · Oct 1, 2011

Hi Linux, Thought you may find this useful:

Vehicle Cable Ratings and Uses.

Notes:-
1) Wiring carrying an electrical "load" will experience a small rise in temperature. For this reason, wiring is often rated in amps using the phrase "for continuous use."
2) The first number in the wire grade column refers to the number of strands of wire. The second number refers to the thickness of each strand in thousandths of an inch. The following table gives some metric equivalents.
3) Use these sums to work out current and power:-
Current (I) = Volts (E) / Resistance (R)
Power (W) = Current (A) x Volts (E)
Current (A) = Power (W) / Volts (V)
For example, a 55 watt headlamp will draw 55/12 = 4.59 amps. (Remember, you will have 2 headlamps in the circuit!) Fitting a 75 watt headlamp would increase the current drawn to 75/12 = 6.25 amps

Wire diameter	Wire cross-section	Continuous Current Rating / Uses

9 / 0.30 mm	0.65 sq mm	5.75 amps - Side lamps, tail lamps, reversing lamps, horns, etc
14 / 0.30 mm	1 sq mm	8.75 amps - Side lamps, tail lamps, reversing lamps, horns, general wiring.
28 / 0.30 mm	2 sq mm	17.5 amps - Headlamps, fog/driving lamps, windscreen wiper motor etc.
44 / 0.30 mm	3 sq mm	27.5 amps - Charging cable, battery feed, etc
65 / 0.30 mm	4.5 sq mm	35 amps -Charging cable for alternator, dynamo, etc
84 / 0.30 mm	6 sq mm	42 amps - Charging cable for alternator, dynamo, etc
97 / 0.30 mm	7 sq mm	50 amps - Heavy duty alternator, etc.
120 / 0.30 mm	8.5 sq mm	60 amps - Heavy duty alternator, etc.
80 / 0.40 mm	10 sq mm	70 amps - Heavy duty alternator, etc.

37 / 0.71 mm	15 sq mm	105 amps - Starter/ Battery cable
37 / 0.90 mm	25 sq mm	170 amps - Starter/ Battery cable
61 / 0.90 mm	40 sq mm	300 amps - Starter/ Battery cable