UKSaabs

My mention of a mod to my car to change the backlight colours on the foglight switches (red for rear, white for front) got some interest in the Projects sub-forum.

As that forum is not for tutorials, I hope this post may be of use

When I converted my lights I used a stock of 3mm LEDs with internal resistors which can be powered directly from 12v. The types I used are relatively expensive and no longer seemingly available. This HowTo uses standard parts available off the shelf at Maplin



Acceptable resistor range is about 850 ohm minimum - brightest - to about 1500 ohm max (dim). In theory at 12v you can go as low as 680 ohms with a modern LED but at 14v peak this is pushing your luck





Would be slightly brighter than the Saab standard filament bulb and use a fraction of the power, and last a lot longer, But nobody would ever know you'd gone to the effort of this conversion if you use green.

























Important note. The two bottom pins only power the light when the switch is switched off. If it doesnt light first time, press the switch!

the Green and Amber test images are actually using a 5mm LED. It will - JUST - fit in through the gap, but I dont recommend it. Using an external resistor is pushing the limits of the space inside a Saab switch

If you want to do this you should put the LED in the bulb holder without a series resistor and cut into the loom negative lead to the lighting pins on the plug and put the resistor in series there. Dont put it on the positive feed as the light switches to a different, higher-voltage positive feed as the switch is turned on!" thats why they get brighter then.