[RICK LAKE]

mercoupe50 If this is at idle, you have too much of a load on the charging system. What is the ampage of the ALT? Make sure the battery terminals are clean and tight, Make sure you have a good ground between the motor and the frame of the car. You said a 460 race motor, are you running MSD or other ignition hi output? These suck alot of amps from the charging system. If you are running under drive pulleys, the ALT is not spinning enough to charge the system. Raise Idle to 1,000 rpm is the problem gone? If yes idle or pulleys driving the Alt too slow, If not regulator is going bad. There is no 100% way to check the regulators and Alt's, except under heavy loads for long periods of time. Start with the main connections at Battery and Alt. wiggle them, make sure there is no movement then goto what's listed above with the rpm's. What other loads are on the electrical system when this happens? Lights, Coolant Fans, Heater Fans, Radio, AC system? you get the idea. Come back with what you find. Good Luck Rick L.