Hello and thanks for taking time to read this. Just finishing a 455 cid swap into my 1969 Cutlass S. 2 generators both checked ok on the bench, yet fail to charge the battery in the car, have a dim GEN light on. Car stops if I disconnect the battery, no detectable electro magnetic field present at generator in car when running, ( yes belt is attached ). Should add, put in a new wiring harness, new voltage regulator which required adding a diode relay otherwise car would stay running with ignition switched off. This car is a convertible and it's nice out HELP!

thanks!

 

Sounds like maybe the alternator isn't getting the right signal on the Field input.
Also, if things are wired correctly you shouldn't need an external diode.

Since you have a new wiring harness, I would start looking there to make sure all the connections are correct as the two things above may be due to the same issue.
I once had the two prong plug on my alternator connected backwards and I had no charging and the ALT light was on.

 

I would agree, but my electrical knowledge is limited, the plug will only go in one way on mine, so don't think that's it, but would agree with you, possible fields crossed, or simply put, just not wired right. Because its convertible weather, I think I'll stop puzzling on it, and take it some place close to get it fixed.

Thanks for your time taken to reply!