I have a 1967 Oldsmobile Cutlass sedan that the previous owner installed a 350 in and a 3 speed automatic. Whenever the car is off, the GEN light is on and I'm able to use the radio, AC, and lights. This killed my battery when I went on leave. I charged the battery but the light is still on even if everything is off. When I start the motor, the GEN light turns off. Any ideas on the problem?

 

With the engine not running, disconnect the regulator. If the light goes out, it's probably a shorted diode in the alternator. If it doesn't, it's probably a short in the regulator harness.

 

Is the light on dim or full brightness?

If it's dim, and you can use all that electrical equipment, either your ignition switch is bad or you've turned it to ACC position. Lighting isn't affected by the ignition switch though- it feeds straight off the battery at the junction block underhood.

If it's on full bright with ignition switch in positive OFF position, you have a bad alternator diode as Ozzie says.

Tell us more about this 350/350 swap. Is it an Olds or Chevy engine, and how much wiring modification did the PO do during the swap? I tend to be leery of engine swaps unless I know who did it or did it myself.

Also- is this factory radio or an aftermarket setup? Again, leery of any PO's electrical work.

 

The light is on full brightness with the ignition in the OFF position and they key out. It's and Olds 350. I got the car from a dealer who bought it from PO and I'm the 3rd owner on it. The car was well taken care of so I didn't ask much about PO. The radio is the original with the 8 track player.

 

I'm betting on an ignition switch or ignition wiring related issue. An engine swap would not have resulted in a wiring change. Since the engine turn off with the key it may be related if they changed the wiring for an aftermarket distributor, like an HEI or an MSD box. Does the car have an aftermarket alarm?

 

Have the alternator tested, off the car if possible. A shorted diode will definitely cause light on with switch off and will also discharge the battery as you've described.

If you can get the alternator on the car rebuilt, do that. If you end up getting a parts store alternator, make sure the parts monkey gives you the right one for external regulated alternator. Double check the two-wire plug- external regulator plug looks like I I , later internally regulated plug is -- . An internal regulated alternator hooked to an externally regulated car will create a lot of charging system havoc.

You at Parris or up at the air station?

 

I'll definitely look into testing the alternator and possibly replacing it or rebuilding it. I'm on the air station. And there's no alarm