I have fitted a new alternator (after 2 from a scrappy) to my 2.0l Pinto but I cannot get the ignition light to go out or the alternator to charge. The Alternator has the 3 spade terminals on the back, the 2 large ones connected together which I have connected to the starter motor terminal which the battery +ve goes to, and the small terminal to the ignition warning light, which is then connected to a switched 12v supply. I have checked and double checked. Any help appreciated.

John

Some things that you could check.

I have heard the following (dunno if I understood correctly):

Check if the smaller terminal has 12v when contact is on. This tension is needed to build up an electrical field. This electrical field replaces the magnets in the older type alternators. Without the electrical field the alternator does not work.

I had the same kind of problem with my Mercedes 250TD. In my case the rectifier was broken, and the ignition switch shorted / malfunction.

Hope this helps.

weird; sounds like all is wired up correctly.

the battery goes to one terminal of a solenoid that is swtiched on when the ignition switch is put into starter position - there is a small wire to the solenoid for this purpose.

ensure that you have a good earth from the alternator body to the battery. if you have painted the alternator mounting brackets then you need to scrape them to bare metal where the bolts go.

as ^^ you need to check that you are seeing 12 V on the wire from the bulb and ensure that that wire is not earthed BUT only connects to the third small terminal on the alternator.