relay and switch ?????

**Aaron Ham** · 12-27-2005, 08:17 PM

i have a GM car. In the fuse panel there is a starter feed fuse, If i take the fuse out the car does not crank. So what i did was trace the wire under the dash cut it in half and put a switch in line with that wire, so i could have a starter kill.

i was told that i should use a relay with the switch because the switch can't handle the current/amps and may soon fail.

My question is how would i wire the relay with the switch so the relay could take all the current/amps.

**binary.h4x** · 12-27-2005, 08:19 PM

what is the rating on the fuse you pulled? and what is the rating of the switch you put in?

here is a whole list of starter interrupts that you could do:

http://www.the12volt.com/relays/page2.asp

**Aaron Ham** · 12-27-2005, 09:22 PM

the fuse is 5 amps the switch is a magnetic reed switch don't remember the amp rating.my alarm remote start has a built in starter kill. Say if i'm sitting in my car listening to cd/dvd etc., and some one try to jack me i can maybe take out the thing that as the magnet in it out and run. I get away and they can't start the car. HaaaaaHHHaaaHaha hahhhahh ahha

**Aaron Ham** · 12-28-2005, 07:05 PM

help me please

**binary.h4x** · 12-28-2005, 07:28 PM

there ya go, hooking that to your starter will only stop a theif from starting the car (unless they have time to find your wiring)

If you want total control over the car, I would suggest a switch on the fuel pump. That way if you get jacked with the car running, just flip the switch and run.

I think in most cars the fuel pump is already equipped with a relay, which means you just gotta cut the wire and put in a switch.

**mushin** · 12-28-2005, 07:33 PM

Originally Posted by Aaron Ham

help me please

Bah, alright

I think the reason no one's really come forward is that your question is so trivial (and I don't mean you any offence, we're all neophites at some point, but if you look up basic relay operations on google or whatever, you should be able to figure it out.)

So you want to switch the starter line using a reed switch? Quite likely it can't handle 5A, so the advice to use a relay is good. You need to get a relay that is rated at least 5A @ 12V (most automotive relays will do.) Now wire the reed switch to power the relay coil. Then wire the starter line through the relay - when the reed switch closes, the coil will get power and close the relay, which will engage the starter line.

edit: looks like binary beat me with a much more useful diagram. I'm leaving now :P

**binary.h4x** · 12-28-2005, 07:42 PM

Originally Posted by mushin

Bah, alright

edit: looks like binary beat me with a much more useful diagram. I'm leaving now :P

what? No more debating over physics?

**Aaron Ham** · 12-29-2005, 01:25 AM

is this correct

**PatO** · 12-30-2005, 01:12 AM

Do you want the relay NO or NC? I'd say NC (pin 85a) - so that when the relay has no power, the car runs (like normal). When you close the switch, the relay is charged and breaks the starter(or fuel) circuit. Relays aren't meant to be charged 24x7 for years on end (I've had Bosch relays overheat during meets and boy is it embarassing!)

If the theif gets smart, he'll disconnect the battery - thus enabling the starter(or fuel pump)! But then the starter won't turn... <doh!>

My point is - if you're going to use this thing during a jacking, cool - go for it. But if you want to use this on a daily basis, get some sort of a "latching" relay. Search on that word for more info.

**lez** · 12-30-2005, 03:34 AM

Originally Posted by PatO

Relays aren't meant to be charged 24x7 for years on end (I've had Bosch relays overheat during meets and boy is it embarassing!)

Some are on all the time the car is running, IE fuel pump relay, power window relay...

possibly some are made for longer duty times, like some are made for higher ampage.