Here's the low-tech, non-electronic fix.  The part you want is a "Negative =
Temperature Coefficient Resistor"  a NTC.  Put these in series with your la=
mps, they are available with a starting resistance of a few ohms to hundred=
s of ohms - for a 12V system pick a range of 20 ohms or less (or they will =
never heat up)

When they do heat up, they go to almost zero.  An added benefit, it will ad=
d life to your lamps.

Randy

> Date: Tue, 17 Feb 2015 00:58:51 -0500
> From: picdude3@narwani.org
> To: piclist@mit.edu
> Subject: [EE] Automotive power surge fix?
>=20
> Recently got and old car roadworthy and it has HID headlights in it. =20
> The bulbs have an interesting behaviour in that when first turned on,=20
> they emit a quick flash of light, then instantly dim, and slowly=20
> brighten back up to operating brightness.  What's not good is that every=
=20
> so often, that initial flash causes enough of a power surge to knock out=
=20
> the ECU (=20
> http://www.wmsracing.com/wmsweb/SDS-WMS-SDS-Digital-Injection-System.html=
 ). =20
> Or perhaps it's knocking out the aftermarket ignition system (=20
> http://www.jegs.com/i/MSD/121/62152/10002/-1 ), as after the surge, the=20
> ECU shows "RPM error".  I'm planning on adding some type of filter to=20
> the ECU or ignition module power lines (no prob with that), but=20
> wondering why I shouldn't try to reduce the surge instead.
>=20
> How would I go about doing this?  The HID lights have the bulbs, a relay=
=20
> module and a couple ballasts.  Would there be a simple way to reduce the=
=20
> surge for bulbs like this?  Or would doing so impede the bulbs operation?
>=20
> Cheers,
> -Neil
>=20
>=20
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