three miles down the road gen light comes on WTF?
took the alt off took it to thw different places both said its fine bought a new voltage regulator still not charging took alt back off bought a new one charging fine but the IDIOT light still on whats that all about? is there a DR. in the house??????

Make sure your battery cables are tight. Loose negative will discharge.

Double check all connections and check all GROUNDS. A bad ground at the instrument cluster will cause idiot lights to come on...ask me how I know

Did you check that your battery is fully charged and in good condition and the terminals are tight? If your battery is not charged of in poor shape, replace it or charge it with a battery charger not your alternator. Are you getting 14 volts at the battery when the engine is running? Does the light come on when you turn on the ignition switch with engine not running? When you start the engine does the light go out then come back on a few miles down the road?

The idiot light is ignition switch controled and voltage operated. When you turn on the ignition switch the circuit from the voltage source at the ignition switch, through the idiot light to #4 pin at the regulator out the F [field] pin to the alternator is closed. As the engine is not running and the alternator is not generating, the voltage at the ignition side of the idiot light is higher than the voltage at the regulator side of the light and the light illuminates. When you start the engine and the alternator starts to generate, the voltage at both sides of the idiot light are the same and the light goes out. If the voltage at the regulator side of the light is higher than the ignition side the light will once again illuminate. It will only illuminate if one side has a higher voltage than the other, if the alternator is puting out more than the ignition voltage it lights and if the ignition switch voltage is higher than the alternator voltage it lights.

The ignition switch gets its voltage from the bus [junction] near the horn relay through the firewall junction block. Any bad or corroded conections [there are lots]in the charging ciruit anywhere from the battery to the switch and back to the battery may create a lower than output voltage resulting in the gen light illuminating.

As you have replaced your alternator and voltage regulator and you say it's charging the battery I would think you have a voltage drop somewhere in the system due to a bad connection, bad ground or faulty component such as the ignition switch.

Try checking the voltage at the Batt terminal of the alternator when engine running, should be 14+volts, then check the battery voltage should also be 14+V. Check the voltage at the fuse box and the ignition switch and if you can the voltage at the juction to the instrument panel, there should be very little voltage drop. Check all fuses and conections.

With engine off and ignition switch on, try removing the regulator plug and checking the voltage at # 4 pin it should be 12 volts if not the problem is in that circuit. [I just went through the same problem, mine was a faulty lamp connection.].

Dr. drivability was right on the head bad ground on the cluster f'n light went right off!!!!!!!!!!! thanks brotha!!!!!!!

No, problem...9 times out of 10 electrical problems on these old systems can be traced back to a bad ground...glad you found it!

One thing have noticed is a lot of people do not have the small neg battery lead from the neg post to the RH fender. This will help better ground your lights etc. because not all the ground straps from the engine to frame are always there and may not be clean.

i have a 69 firebird... new bat and alt... been tested a few times and both are good... battery is still draining. My question is would a bad horn relay cause a charging issue? (i hit the horn button and all it does is make a clicking noise)

Absolutely, Same problem, changed it out with another one I had off another car ,problem solved

ok ill change it out and see how it goes. my buddy (who builds race cars) told me to just run a wire from the hot post in the alternator to the battery... will this be a temporary fix?

Tell your buddy you'd rather your car not have an engine fire, thank you.

lol yea true, i took it to a shop my company sends all our cars to, to see if they can give a dianostic on what actually is going on and if there are other issues too