1994 850 - Hazards on by Themselves, Car Won't Start

[jjs70pdx]

1994 Volvo 850 Wagon (non-turbo)

I have had a repeat issue the last few weeks, once a week - coincidentally in the same parking lot both times. A day prior to this issue, I had one instance of the car stalling at a red light, then it started again after two cranks. The next day I was running errands, came back to the car and the hazards were flashing on their own. The car would not crank/turn over at all. I ended up disconnecting the negative battery cable and the car was fine and started up after that no problem. I also replaced a very outdated battery from the previous owner that was going on 7 years, thinking that might be the culprit of the issue. That did help with better cranking power, and I have not had any more stalls at stops or otherwise.

It did the same thing yesterday so repeated the neg. cable disconnect and that solved it once again.
The only thing I can correlate to both instances was that I kept the front windows down and engaged the auto locking system by hand. I also reset the service light a few weeks ago, but I don't think that's related to any of this. I do not have a working fob, so it's just my key that I usually use. I've owned the car a little less than a year and it's going on almost 195k miles.

Suggestions on what to troubleshoot/fix so that the hazard issue doesn't persist? Thanks.

[matthew1]

Sounds like you had two problems.

Battery causing stalling. Fixed.

The second is the S70's 850's alarm triggering, but the siren has probably been removed, like my 850's is. They tend to fall off.

My 850 will decide to trigger its alarm -- of course while parked, locked, armed -- at random times. It's silent, but hazards flash. I have a sensitive (thenthitive?) 850. When this happens, disarm the alarm by unlocking a door with a key. Then the ignition will fire.

I haven't gotten around to track down the alarm sensitivity. Bigger fish to fry.

[Ozark Lee]

If you have the windows down, the car locked, and reach in and unlock the door from the inside it will trigger the alarm and the immobilizer every time. That isn't a flaw, it is by design. The standard alarm doesn't have any motion sensors or proximity sensors, it is triggered by any door, trunk, or hood being opened without the used of either the key in the door lock or via the remote keyfob.

...Lee