Volvo: Battery Drain, airport parking lot, electric cooling fan

Question
I have a 1996 Volvo 850. Over the past several months, I have left the car unattended for a few days in an airport parking lot. When I returned, it wouldnt start. This is similar to a problem reported to you by another user.  Each time, there would be some power, as in the radio and even the headlights would work, but the ignition wouldnt turn over.  I have replaced batteries and have had the positive battery cable replaced.  The problem still exists.

I replaced two batteries and the last time this happened, I had it tested, and it had some charge.  My repair shop replaced the positive battery cable as there is a history associated with the cables.  Nothing seems to work, however as the last time I left the car unattended, the battery drained.  

Nothing is wrong with the alternator and there have been no added electric components that would contribute to the battery drain.  What can I do now?  

Answer
Mike,
Well if the battery goes dead while sitting there has to be something draining the battery. If it (battery) just sat for two to five days not hooked up to anything it would not go dead, right! So there is somethng that is draining the battery. I have seen trunk, glove box, interior lights that drain the battery. There was even the time it was the alternator that caused a drain. If your car has a SAS secondary air system, there is a relay for the air pump it is mounted low on the left front of the car. The relay gets wet and corrodes and shorts out, causing a drain. Another thing to look at is the electric cooling fan, the relay for that top of radiator and at times they cause the fan to come on while unattended.