Starter Trigger wire Current Draw?

**takai** · 06-11-2005, 06:09 PM

Alright, just a quick one for the leccies out there. What would the max current draw be for the trigger wire of the starter motor. The starter runs fine with 120A going to it, but the trigger wire will be going through a 16A switch on a 15A fuse... enough?
Opinions?

**oldcorollas** · 06-11-2005, 06:18 PM

what is the resistance of the solenoid??

**takai** · 06-11-2005, 06:22 PM

No idea, anyone for the solenoid resistance for an AE92 smallport 4AGE starter?

**roadsailing** · 06-11-2005, 07:19 PM

you got a multimeter?

i think the current would be fairly high, judging by the sparks i have seen when jumping starters with a screwdriver.

just use a fuse big enough to protect the wire, and use a relay like the standard setup. switches are not reliable/good over a few amps.

**takai** · 06-11-2005, 09:38 PM

15A is quite easily enough to create a fairly large spark, and from what ive seen a lot of setups use a momentary switch based rig which is much more stable under load than a permie.

EDIT: i guess ill just pop a 15A fuse in there and give it a go, if it works all is well, if not it wont be hard to pass it via a 30A relay.

**wagonist** · 06-11-2005, 11:30 PM

No car I know of has the starter trigger circuit going through a normal fuse, & certainly not something that low.
I'd be using a fusible link instead.
I've also had to wire up a few cars (mine & mate's cars) with a relay, because the resistance from the battery, through the ignition switch, & then back to the starter was enough for the solenoid to not work anymore.
But using the trigger wire to operate a relay with power then straight from the battery to the starter. Bingo, starts first go, every time (barring no other problems of course)

Doing it this way also means you can reduce the size of your wiring saving a few grams

**takai** · 06-11-2005, 11:36 PM

Doesnt really save any grams, the relay woudl compensate quite easily.
The 30A wiring would only be an extra 15cm max from where the relay would be located, so that isnt an issue whatsoever.
Ill give 15A fuse a go, if not ill just relay it.

**The Witzl** · 07-11-2005, 08:00 AM

give it a 30A fuse.
the solenoid can draw up to 50A instantaneous current, and the starter motor itself can draw up to 500A instantaneous current...... but typically the continuous draw is around 20A and 150A respectively.