90GTRagtop

Still sounds like a bad alternator from the charging issue to me. Since it's OK cold and goes out after ½ hour, it may be that there is a resistance build up at some electrical junction. As it heats up, the resistance increases, thus making more heat and eating more current, until a balace is achieved. It is possible that the problem junction is not inside the alternator and it is simply maxing out the alternators output capacity. If you still suspect a ground issue, one thing you could do is to use a digital multimeter and check the voltage potential between the alternator housing and the battery - post when the alternator is hot. (Obviously you must be careful with the loose wires near running engine belts and pulleys). It should read 0 volts. If there is a voltage drop, then there must be a resistance between the althernator and the ground.

Pure5.0

One of two things:

Your alt is going bad (which could very well be the problem). I had a ford escort once and the alt went bad so I got another rebuilt alt...that was bad too (smoked) then got another...that is bad also. Rebuilt seems to be bad news for stock fords.

Also some electrical device in your car is pulling too much juice...could very well be from a short. Causing the alt to run and run and run until it just burns up and can't physically charge anymore because of the reaction of the heat.

A car should charge anywhere from 14.4 to 12.8......any higher than that and any lower means the alt is peaking....sure tell signs of an alt going out. Watch your guage (voltage) and see if the volts are up high at one point and low at the other point.

Poor charging will cause the car to idle and die. Ford put very small stock alts on and in order for them to work good they need a high volt (ex 13.8, 14.2) just to keep the car running smooth or it starts to be affected.