while driving on hwy,, engine died, ( lost power to almost everything, steering, brakes, windows, engine, etc)
drifted to side or road. Car has lights, and horn.. thats it. Battery is ok, cables ok, no juice to starter, etc.

must be a major in line fuse somewhere??

It was hot, and was using airconditioner on max.. noticed volt meter was registering below 12 V while driving, with air on max and fan on high.. If cut off the air, it would go backl up to 13V Now registers 0 with ignition switch in "on" position. This is a new one on me.. Dont have a clue what the problem is.

It reads like the alternator is outputing low on current, or the IAC doesn't kick in to increase idle speed to make up for the electrical load.

As for electrical power, you might check the fusible links at the starter solenoid for continuity and or clean connections.

The elctrical side of the ignition switch could also be broken or contacts carboned up from sparks making for a high resistance.

thanks.. checked fusible link at starter and it was trashed from heat or just plain old age.. Are there any more to check or is that one it? What would cause it to short out electrically? Are fusible links common problems for 84 Zs? Where is the IAC and how do I ceck it out?

thanks.. Where is the IAC and how do I ceck it out?
Your welcome. My mistake, yours has no IAC, its carburated.

As for fusible links, I believe they are only at the starter. You might get a Haynes manual and use it for reference.

you were correct again.. changed 2 fusible links and alternator was still outputing low volts when ac was on. so will replace alternator..

Can I replace with a higher rated output alternator wthout causing problems??

Yes, change belt as well.

changed out alternator with new delco, changed belt, repaired fusable links, took it for a drive, and burned up the fusable link at the starter again.
I cant seem to find the short.
Now Im depressed.

Check all the connections to find those having been melted. They probably are corroded which draws extra unwanted current. Feel the heat.

Write down the circuits not working, then compare their power source from the book.

Could be the fusible link was too small is wire size, maybe not.

Install a test lamp between a battery post (+ or -) and it's clamp. The light bulb in the test lamp will limit the current flow to a few milliamps while you disconnect various connection points to isolate the short. Disconnect the alternator field lead, starter lead, firewall connector, and even fuses as examples of how to isolate the circuit. When you find the offending circuit the lamp will either burn real dim or go out completely. The ignition may have to be on to do the test.

There should not be a fusable link between the hot lug of the starter and the positive supply. Although the vehicle electrical system may tap off the lug with fusable links to feed other circuits in the car.