So recently my lights died when driving (at night!) an when I got home it turned out the battery was not charging - also I then realised the charge light was on (its covered by the tacho but I saw it lit when I had a proper look).

So first off I knew the car had already a solid state regulator (so I assumed it was ok as it was newer than the 32 year old Alt). So I got a new alt and hooked it up (old alt had #OOPS#ed bearing/brushes and the coil read a little on the low side - possible short).

Once I started it I checked the battery voltage (same as when the engine is off) so I knew the damn thing wasnt charging.

Next I performed the Regulator bypass test - I powered the field coil from the +ve battery terminal and when the motor was on you could hear it bog down under load and the mulitmeter showed it was in fact charging.

I also checked the continuity of the cables between the reg plug and the back of the alt and all of them were ok. I could measure 12v in the plug when the igntion was on and I could also power the charge light by shorting it to ground.

Everything pointed to a buggered reg seeing as the cables and alternator were ok.

Next day I got a new reg. The guy in the shop said they had trouble with the electric regulators and I then brought the mechanical type one (brand new). The plug on it was identical to the original and the wire colors all matched up. Once I installed it I started the car and the charge light was still on! Even the DMM across the bettery showed no charge!

What on earth is wrong? Has anyone repleaced both the alt and reg and still had this trouble?