Mustang voltage regulator hot

[gui67]

Hello,
A friend of mine has a 68 Mustang. the wiring harness is a new AAW.
The alternator is charging, but the VOltage regulator is warming when the key is off, which seems very strange.
I am not used to Ford electrical charging system, so I prefer to ask.
everything seems to be wired correctly.
A goes to battery positive on the starter relay.
F goes to Alternator Field
S goes to Ignition 12V.
but as soon as the battery is wired, it gets hot.

Is there something we should check? It is brand new, I think it is a solid state with the resin at the back. Or should we replace it?
Thanks
Guillaume

[Tim C]

Ford used 2 different wiring setups on the 1g alternators with external regulators, depending on wether it had a warning light or an ammeter. The way you have it is correct for an ammeter setup. For a warning light setup, a goes to the starter solenoid battery hot, I comes from the ignition switch through the warning light (don't use a LED for this and put a resistor parallel to the bulb so it'll charge if the bulb blows), f goes to field or fld on the alternator and s goes to stator or sta on the alternator.

Most aftermarket regulators can be swapped interchangeably, but Ford did use a separate part number depending on how it was wired originally, I'm not sure if your regulator is universal or not, that's something to check.

Even if you don't run a light, the way you have it should work provided the regulator can work that way.

Either way it should not be getting warm with the key off, that shows a current draw through it which will kill the battery.