So I will try to be brief. 2000 s80 2.9 been sitting since everyone has been in lockdown. So I charged up the battery been driving it around to get the rust off the brakes. Today was going for a sticker so checked all the lights. The license plate and marker lights were burned out so I replaced them. Took it for sticker passed left happy came home and parked her. Went out a little later to pick up some dry cleaning returned home no problem. Tonight I notice the alarm light is not flashing. Try to lock the doors but they are already locked. Use the key open door no lights insert key nothing no lights no sounds nothing just darkness. I will check the battery with meter as a first step but what would be next.

 

Time to put your multi-meter to use. Start with measuring battery voltage a flat battery is going to be close to 12V, a battery with a bad cell is going to be 10V or less. Then get a jump start and measure voltage with the engine running - should be 14V or more. If less than 13 you may have alternator issues. Finally, with the engine off, disconnect the battery terminal, put your meter in series (ie battery post to meter, meter to cable) and measure the current draw with everything off. If its more than 50mA you have something that is draining the battery. That's when you start pulling fuses etc to isolate some circuits.

 

Battery was dead this morning must have bad cell was lower than 10 volts it’s on the charger now so I can try to start her and check with meter if alternator is charging. If alternator is working it should get like 14 volts at the battery correct. Should I start by replacing battery it was under a volt when I metered it this morning.

 

What battery cable do I use and what setting on the meter?

 

I'd use the negative post to minimize the risk of having the cable touch something and shorting out. You can also probe using the relay/fuse box. Plenty of how to vids on Youtube just search for "parasitic current" etc.

 

Thank you for the responses. Alternator was dead but also radiator fan runs constantly now that battery is charged. It must have drained battery I have unplugged for now while it is just sitting in driveway. Is there a way to repair the module or do I need a whole new fan.