hi Steve.
I had the same problem. bulb and fuse OK. I checked the bulb socket I had +4v with reverse selected and deselected and ign on. 0v with ign off. I removed the plug from the gearbox switch and jumped the two wires and hey presto the bulb lit.
So it's the gearbox switch in my case..
I've had horn problems in the past due to driving through floods. The reverse light switch is co located and lower down so I suspect driving through deep water has caused the problem. I'm going to put an illuminated switch on the dash rather than replace the gearbox switch since I use fords (water crossings) a lot.
Hope this is helpful.
Paul
Paul, December 2007
