86 Truck Brake & Fuel Lights On

[amarts]

I have a 86 half year modle hardbody truck with a V6 engine. It has been extremely dependable with over 250K miles and only minor repairs. A few days ago my Brake & Fuel lights came on at the same time. My mechanic I have had work on the truck in the past doesn't know what those lights on together mean. The first day they came on, they turned on and off at the same time several times. After that day, they come on when the engine is started and never go off. Fuel level is fine and I don't believe the brake has a problem. Engine runs fine, just those lights on. Does anyone know what the Brake & Fuel lights being on at the same time means?