Volvo 850 Battery drain from security system?

I’ve got a wonderful 1997 Volvo 850 named “Fey” but Fey has a problem. She keeps wanting to sleep in each morning. Sleep until I give her a nice jolt from our other vehicle.

I already tried a battery “transplant” but the problem still occurs.

My mechanic couldn’t find anything but I caught a good clue one day when I was watching her from inside my house and the yellow lights started flashing like the alarm had gone off. But the horn wasn’t sounding. When I went out and unlocked the door, the lights stopped flashing.

On a hunch I tried leaving her with the drivers door unlocked for a couple of weeks and sure enough the battery problems never resurfaced.

When I went back to my mechanic they tried changing the security system relay, but when I leave the door locked it still happens.

Does anyone know what I can do for poor Fey?



You have done a good job in describing the problem and I think I know what is going on. It could be a couple of things that I can think of.

First off, the alarm system will make the lights flash like you describe when power from the battery is disconnected and then reconnected. The alarm system will need to be reset by unlocking the doors just like you describe. This means there may be a intermittent power connection to the alarm system somewhere. I would go over the main power connections from the battery and the main power panel under the hood and look for bad connections.

The other way this might happen is a door switch or anything that can trigger the alarm has an intermittent short problem and triggers the alarm. Now, if the alarm is set and say a door is opened without turning the alarm off and the horn sounds along with the lights blinking, this idea is most likely not correct. The faulty switch should sound the horn also and that doesn’t appear to be the case here. So really, the intermittent power problem seems to be the culprit here unless, the horn doesn’t work, or sound when the alarm is triggered.

Thanks. The horn does go off when I purposefully set the alarm off so I’ll start with the power supply idea.

Could it be something as simple as the fuse for the security system?

It could be anything that is in the power supply path, and that includes a bad fuse connection or connection to the fuse, providing power to the alarm system. You may be able to track the trouble down by tapping on suspected areas using a screwdriver handle to tap with. The vibration trick works pretty well finding intermittent problems.

Don’t lock the doors.

The other option is to spend however much money it takes to diagnose and repair this problem. it scares me to think about it.