Diagnosing alternator help

[MadProfessor]

Hi guys

I recently bought a luxo-shed of a 1996 LS400. It's been running fine until yesterday when all of the warning lights would come on whenever I didn't have the accelerator pressed, but would instantly go off whenever I gave it a little gas. This morning the car wouldn't turn over although the lights and other electrics would come on (e.g. radio). This afternoon nothing at all electronic works e.g. not even the remote central locking.

Obviously there's a fault right now with the battery being dead but how do I determine if it's just the battery or instead the alternator not charging the battery.

The power of Google reveals that a common fault is the power steering pump on these cars leaking onto the alternator.

Any tips of how to differentially diagnose the fault.

[shoehorn]

The first thing to do would be to run the car and check that there is sufficient charge being supplied by the alternator by use of a multimeter or such.

[andyiley]

With the engine running you should get around 14.5 volts at the battery, any less is either a loose connection, poor chassis/battery earth or goosed alternator.

[jackwootton]

If you charge the battery to full, and run it on a different car (if you have one), you'll be able to tell if it's the battery that's dying. If it works fine on the other motor but still gets drained on yours, I'd assume that the alternator is dead. There's plenty of people that break LS400's for the engines (off-roaders), and run 24v alternators on them for the winches, so you'll be able to get a second-hand working alternator cheap!