Hi all, I have an electrical problem that I hope you can help with. When I turn the car off and remove the key the red “gen” light stays on, on the dash. (Drains the battery)
if I disconnect the battery, I hear a click, then if I reconnect the battery the red light is off.
1968 442
i have only had this car for a couple of years.
it has had some after market adders. Here is a pic
let me know what additional info you need to help me resolve this issue.
Thanks

 

Probably a bad diode in the alternator.

 

I was thinking alternator diode as well. Instead of disconnecting the battery, try unplugging the harness from the alternator. That will tell you if the issue is in the alternator or not.

 

The light is fed by the voltage regulator brown wire. It could be a bad VR.

 

I had the same thing happen on my 66. Replaced Alternator, all good. Had to be a bad diode.

 

Okay thanks guys. I will try replacing. I wasn’t sure if the connectors at the back of my alternator were correct. I have attached a picture. Also, how do I know if this is the right alternator?
Cheer

s

 

Try to isolate the problem. It could be a diode in the alternator. It could be the regulator. That "click" diagnostic you provided makes me think about the regulator. Only one needs replacement.

 

Thanks Ozzie,
How would I figure out if its the regulator or the alternator?
How do I isolate the problem?

 

Try unplugging the white wire from the alt. If it clicks and the light goes out it is probably the alt diodes.

 

If it is a diode at fault, it will be a positive diode. You can check the positive diodes located in the heat sink as follows:
1. Attach a positive test lamp to a diode lead.
2. Attach the negative test lamp lead to the heat sink; the lamp should light indicating a good positive diode.
3. Check the other two positive diodes in the same manner.
4. Reverse the test lamp leads and again check the three positive diodes. The lamp should not light for a good diode. If it does light, that is your defective diode. Replacing the diode should resolve the problem.

If all the diodes check good, the problem is most likely the regulator. Your diagnostic makes me suspicious of it.

 

So, yesterday I finally got back to work on the Olds. I replaced the alternator and the voltage regulator and also put on the correct connector to plug into my he new alternator. So far everything seems to be working as it should.
Ozzie, I didn’t try to figure what was defective, the alternator or the regulator..... but thanks.
When I looked up the costs, I decided to do both. 45 mins ( with one beer break) all was complete.
thanks to all the help guys