Hi Guys

I've always had a good operating Cruise Control on my 760 Turbo Diesel. I don't use it often because most of my driving is local. I recently took a trip to Pa. When I went to engauge cruise, NOTHING.

I started to do some troubleshooting when I got home. Vacuum Pump, Module, Brake Pedal switch, Wiring all good, So what gives? I'm a pretty good Electrician but this has me stumped!

Then I remember an old post on this board. Stating that if the brake lights are out, the cruise won't work. Ah ha! About 6 months ago I replaced the brake light bulbs with these new fangled LED Units. And since then I haven't used cruise.

Well here's the catch. The Cruise Control Module is using the Brake Light filaments as a path to ground. Through the switch on the Brake pedal. The original lamps are very low resistance devices, so the module sees ground. The LED bulbs are much higher resistance devices so the module never sees ground and thinks the brake pedal is depressed, so no cruise.

Thank god for that old post on the Brickboard. The wiring diagram confired it. I'm writing this so no one else will waste half a Saturday, chasing their tail on this. Stay away from the LED bulbs, if you want Cruise Control!!!