Starter Relay Current

Does anyone know of a source to find out actual relay interrupt current for different vehicles?

I am looking to use an alternative to the large Bosch relay.

What are the real currents in the starter switch circuits?

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digs

digs] wrote:

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Does anyone know of a source to find out actual relay interrupt current for different vehicles?

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Only a Helms manual or similar, will tell you what each make, model and model year vehicle will draw for current.

digs] wrote:

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I am looking to use an alternative to the large Bosch relay.

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A standard mechanical relay does not get any smaller for a automotive use. Unless you want to spend twice the amount of money for a smaller *mini* relay.

But why would you??

digs]W wrote:

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at are the real currents in the starter switch circuits?

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A 40 amp SPDT relay will handle anything you are looking into inturrupting for a standard automotive vehicle. If your intent is to inhibit a industrial vehicle such as a Mac Truck, then you can also use any 60-80 amp relay.


Regards

EVIL Teken . . .

If you're thinking about trying some of those "Pilot" type relays to save money, don't you're just throwing your money away.

1. Cut your starter wire.
2. Set your meter for DC amps.
3. Put it inline with the starter wire.
4. Start car.
5. Read the current on the meter during cranking

Will be more accurate than any book could ever tell you..Most meters can take up to 10 amps current. If yours starts smoking, the starter circuit needs more than 10 amps, and you need a new meter. If your meter fuse blows a short piece of door lock actuator rod fits pretty well.

DISCLAIMER: I would NOT recommend this test or procedure to anyone on a starter circuit as you will more than likely fry your meter.


Seriously though what you could do is cut the starter wire and put a fuse inline. Start with a 40 amp fuse..Start the car and see if the fuse blows. Go down to a 30 amp fuse..Start the car and see if the fuse blows. 25a, 20a, 15a, etc..At some point your fuse will blow and will give you a pretty good idea on how much current it takes.

Also to mirror the other posts I would stick with the common relays others have mentioned. Good luck,

Mike

I wouldn't think a starter wire would draw an incredible amount of current- it basically activates a big relay- the starter solenoid.

Yeah, it activates a large relay, a hell of alot larger than 40amps, which switches over to what.... 4 gauge wire with 400amps behind it? to supply a motor with enough power to tear your fingers off your hand? In all seriousness, the standard automotive SPDT relay is cheap as hell these days, will handle nearly anything you toss at it.... what more coulod you ask for? 1$ extra to properly power anything from a snow plow pump, to an amplifier, to a DVD player to a set of neon lights.... 1$... hell even if you go radio shack your looking at 6$ a pop.... big deal... its done right!!

So really, if you wanted to test it out... go invest 300-500 in an inductive DC amperage meter and test it all day long... regardless... your going to use a 30-40amp spdt automotive relay

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real world amperage to activate a starter solenoid would be 10 amps i would have to guestimate - one way to find your particular amperage would be to use a standard automotive battery charger with an amp meter on it, and use the battery charger to activate the solenoid - pay attention to the meter on the charger at the moment of contact, as you'll likely draw (my guess) a 5 or more amp surge higher than the actual "on" circuit use.  however, these guys have it right - the regular bosch relay is an automotive relay, and would be considered "standard" for that kind of use.  it's really not an overkill for that use, and in fact, if anything - the higher rating will mean extend point contact life in the relay versus using a relay closer in rating to the job.  as far as being able to drive the entire starter - forget it.  you couldn't start a motorcycle with a bosch relay standing in for the solenoid.  like mikeshonda750 said, 400A (give or take) for a larger engine, a lot more if it's extra cold, or hot.   figure that if your engine was warmed up and took as little as possible to start it, you're going to pull a minimum of 100+ amps.  if you're wanting to have some momentary contactor with that kind of current rating, i would suggest using a ford starter solenoid - the type mounted to the firewall.