My 89 240 is not holding a charge. If the car sits for a couple days, or you jump the car it will turn on, but wont stay on for very long. I had the battery and the alternator tested, and both passed. What else could be draining the battery like this, but still allowing the car to start after it sits for a couple days after it dies?

 

The only thing it can be is a volt draw. Something is making contact that shouldn't. Check your cables scrupiously. Also, since your's is an 89, you have OBD. Dump the codes and see what if anything is going on.

 

put in a disconnect switch inline on the positive side to stop the drawuntil u figure it out

 

when they checked the alternator
did they check for continuity both ways,
or just for charging
there are diodes that are prob blown
they are like a check valve for electricity
that only allows power to go through one way
i think that if you remove the heavy red wire off the positive post of the alternator
and you put your circuit tester alligator clip on the positive post of the battery
you will find that you get a light when you touch it to the alternator positive post.
which would mean power from the battery could drain though the alternator.
if this is true you will have to replace the alternator.
please try this and let us know what happens
Les

 

Well I replaced the alternator for good measure since I had an extra one sitting around, but found the ultimate problem to be a relay switch for the fuel pump that, so the car wasn't getting fuel