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I have a have a 1996 Volvo 850 non-turbo. For the past year I have had a problem of the battery draining itself over night. I took it in to a mechanic and they said the battery and alternator and everything was fine and they could not find the drain. It will only do it in the summer. The car would be dead 3 or more times a week and would easily jump start. During the winter it did not do it at all. Then as soon as it started to get warm and humid out again it started all over. Currently I just unhook my battery after using it. It would drain the battery over night.

I figuring it is some drain related to humidity and rain fall but i do not know. Anyone have any ideas so i can fix it, thank you  

try picking up one of these

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=97853

intermitants are really hard to find...

you have to duplicate the exact conditions of the battery drain...

so with the hood up.. the hood lamp unplugged if it has one..  the battery disconnect installed ...  leave the drivers window down...   park the car... open the hood...  hook a 12 volt test light across the disconnect terminal..   close and lock the door like you would when you park it ...  unscrew the green knob... if there is a power drain...  the test light will light up....   remember... you are disconnecting one side of the battery by loosening the green knob...  and the test light is across the open circuit...   so any power draw will have to go through the bulb.. lighting it up...

one car would come in the shop for dead batterys all the time... until..  the tech finally did the lock the door trick...   turned out the built in car   alarm that is activated by locking the door... that was on a nissan 300zx...

my mom.. .. just used this trick to find the short in her car...

so anybody who can disconnect the battery could probably do it...

oh.. when you end up with everything off. but the light is on...  reach through the open window..   start wiggling knobs... ONE at a time..

then you can start pulling fuses ...ONE at time... replacing them in the same hole... if the light does not go out...


it is totally possible that a relay somewhere in the car has gotten filled with rain.. or just moisture...