1989 Jeep Cherokee Electrical problem

1989 jeep Grand Cherokee 4.O L
first owner 18 years dealer serviced, less than one year previous owner decided to install a security system and high powered stereo.

He disconnected the security system before I bought it in 2007
drove it for about 8 months was perfect.

Then radiator bottle cracked and killed the alt.

Had a new one installed it was fluctuating wildly. Mechanic said it checked out as well as the battery ~then it stabilized ~then on a hot day ~ ac on ~radio on ~brakes in ~ stuck at a train crossing ~ alt died.

Jeep sat for over a year.

Just had it serviced, new alt, new battery ~ seems good, but the turned on the AC and saw it fluctuating~ dropping slightly. Drove a couple miles then it was up to 14 again.

Concerned since this is similar to what happened with the previous alternator.


Was told the last alt had a very bad short by the mechanic who just changed it out. First time there.3rd alt~ I am thinking it is something else.

I need the car to be reliable enough for 200 plus mile trips through the desert. Plus daily driving in LA.

Engine is great ~no over heating ~ everything, else so far checks out, brakes a bit soft ~ but it's been sitting for over a year. New spark plugs oil change/filter. Lube.

Advice please.