Works with charged battery. Then goes dead. 89 volvo 240

Sound like your alternator is shot. Do the test ..After you charge the batery or get it boosted if you remove the positive battery post OFF the battery and the engine dies right away your alternator if shot .

If you start the car and then remove the positive cable from the battery the car should run off of the alternator. If it dies you alternator or the wiring is bad, most likely the alternator.

sounds as though you have a bad alternator or a loose alternator belt and the battery is not being charged. while the car is running - check the voltage from the alternator and make sure it is about 13.4 volts DC.

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Your alternator is faulty.

hi check/ clean all fuses they corrode /where the fuse connects in the holder i use a phillips screwdriver to clean the brass ends and replace the fuses they (they may and do loose contact under load which will stop the car from charging and flatten the battery good luck hope it works out
regards ray w QLD OZ

If it is the alternator, you will have a dead battery too. Have you charged the battery to see if it will allow you to get to a parts store and have the charging system tested? I would do to that before tearing into the alternator and spending the big bucks. Taking the alternator out is not a big deal, two bolts to loosen and the wires in the back to unhook - after you take the ( -) wire off the battery. Keep the wire connections straight for hooking up later. To get the alternator belt loose, you will need to loosen the adjustment screw until the belt can be pulled off the pulley. Good luck

if with the volt meter the amps go down while running and at increased rpms than your alternator is not charging right

A dead 7 mos battery is not getting re-charged properly. If alt is ok then it must be wires/connections. Sudden death while driving could be related to bad battery condition - thus the reprieve when turning off and starting over. I would have a real volt meter ( not just dash) attached to this car for a while so that I could see what is going on while driving.

If you can get it running again, get it to an electrical shop where they can test the charging system. If the alternator is still bad, it will continue draining the battery. If it won't run, pull the alternator and take it to a shop that can test it.

Down the side of the Engine where the Alternator is there should be a few wires.
1 goes to the oil pressure sensor
Another few wires go to the Alternator there are 2 circuits one is for charging which is a little thicker which is bolted under a nut & a few smaller wires which do 2 things.There is a low current circuit that applies 12v to one side of the battery lamp on the dash & when the enging is running this 12v is on the lamp & the 12v from the battery is on the other side so the lamp is out .
If the alternater isn't turning 0 volts is coming from the alternator & the Battery lamp is on.
These smaller diameter wires are important for the monitoring & charging the battery.
If you can't get the battery lamp & other monitoring lamps on the dash to illuminate when turning the key around to run not start your going to have battery charging problems.
I suggest you check the black plastic insulation carring these wires in them may be cracked or broken.
I own a few 240 series volvo's & I think I have had just about every electrical problem possible.