How do you fix the taillight problems with the Saab 900?

Which 900? The Classic 900 (1979-93) or the NG 900 (1993-97)?
There is a known problem with the taillight ground on the C900 4-doors and convertibles. The solution is to add a ground wire from the taillight circuit board's ground to the body. See www.saabnet.com for the fix.