My '84 F-150 dies when you disconnect the battery, it's not the alternator. Voltage regulator? Any tips would be nice.

1st tip.
Don't disconnect the battery when the engine is running.

yeah vehicles today arent like the old generators when you could do that.. back then the batteries were used solely for cranking over and the generators powered everything else.. today the alternators just charge the battery and battery powers everything else..

Correct^

The battery is in line with the circuit so there is nothing to complete the circuit once you pull that batter out.

The alternator still powers everything as well as charging the battery...one of the reasons they have become larger over the years is the multitude of accessories that they must power while the engine is running.

More is asked of todays batteries as the security system, keyfob, powered windows, hatches etc.

As far as removing a battery in today's cars with the engine running...not a good idea...the electronics are far too sensitive to take transients etc.

In older cars...60's -70's it wasn't that big of a deal.

The DC supplied by a car alternator is actually pretty smooth as it's derived from a 3 phase supply will a full wave rectifier.

a rectum frier?

jebadiah04 said:

a rectum frier?

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You know it!

It is hard on the diodes to do that, but thing is, how can you be certain it isn't the alternator? If it has been tested, or swapped with a known good one, then please share that info. Beyond that, a simple bad connection at the voltage regulator or the regulator itself be bad are possibilities, along with wiring troubles. It isn't uncommon for corrosion on a terminal for the regulator to cause it to fail to operate. There is also a fusible link that could have failed and then there is no way for the power to get to the battery. You can test for voltage at the alternator as well to check for proper operation.

There is an inline fuse right behind the battery in the wire harness. Check it. The inline fuse will make the alternator not charge the battery if it blows, but if it is getting corroded it will slowly charge the battery, but not allow enough juice to keep it running on the alternator alone. It's a wire that has like a square in the middle of it that says fuse.

^^ also known as a fusible link... A quick test is to pull on it, if it stretches, it is burned out.

Fellro said:

. A quick test is to pull on it, if it stretches, it is burned out.

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Just saying,,,,,,,,

That is interesting tho, is it made to be tested that way , or just coincidence ?

coincidence
The wire inside is designed to melt out quickly, and the jacket stays. It leaves a plastic sleve behind.

^ Got it !

Fellro said:

^^ also known as a fusible link... A quick test is to pull on it, if it stretches, it is burned out.

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Sorry about that... Didn't notice you already mentioned it.