Re: QTC: Starter issues

[dan_masi@MENTORG.COM (Dan Masi)]

On Jul 9, 12:42pm, Gary G. Erickson wrote:
>  I took a Bosch 30A relay (the variety that Audi already used
> 12 of in the design of the car) and wired into the starting circut
> as you described.  I know that there is considerably more juice
> there than 30A, but unless you're in the habit of cranking you're
> car for minutes at a time you should be just fine.  (Once as a
> test I disconnected the coil and cranked the car for 45 seconds
> and checked the relay . . . didn't even feel warm!)

I'm jumping in here not having read the original description
of the wiring, but I want to add a general statement here.

A relay which is rated at 30 amps means that the relays *contacts*
can switch 30 amps.  Has nothing to do with the coil, and one
wouldn't expect the coil to feel particularly warm just because the
relay is switching more than its rated current.

You run the risk of heating at the contacts, though.  They will
eventually get dark and corroded, and will exhibit finite
resistance.  With a larger-than-rated current flowing through
them, this in turn translates to heat, possibly a lot of it.
Besides simple reliability issues, there's the chance of electrical
fire when using components for greater-than-rated currents.
I'd be leary...

Dan Masi