Volvo 740 battery dies after it hasn't been used in a while
 

Another problem with my son's Volvo 740. If he doesn't use the Volvo for a period of time, several days to a couple of weeks, the battery will be dead.

It seems like there is a slow discharge of the battery. Is there a way to narrow the problem down to try and identify what is causing the battery to discharge?

In a 1988 Volvo, I suppose the source of this type of problem could be almost anything but is there a systematic approach I could use?

I am going to spend a few days at Christmas to try and fix these key problems. If I cna get he car to be more reliable, I am going to have to recommend to him that he looks a a new vehicle.

Ian (Dad)

If you look in the general Volvo chat section, you'll find a battery drain thread. That should help.

Other than that, it is pretty common for batteries to drain when left idle, especially in this cold climate. You can put a quick disconnect on the negative cable so he can disconnect it when not being used for several days. There may also be a charging issue. Have the alternator checked.

FIRST thing I'd do is a simple charging system test.

1) volt meter across the battery after its been parked a few hours, you should see something in the 12.6VDC range at room temperatures (68F) but even a fully charged battery is quite a bit less if its really cold....
2) key on, make SURE the alternator light comes ON.
3) start car, make SURE the alternator light goes OUT.
4) with car running, measure that voltage across the battery again, it should be at least 1.2 volts higher than the reading in step 1.

if so, then your alternator is working and charging the battery.

tracing down voltage drains can be fun (insert sarcasm smiley here). it can be things like trunk lights, poorly installed after market accessories, etc. amateur hack-jobs in the dashboard or engine wiring, ugh.