My wife's 240 wagon recently started acting odd. While driving along, the rear defog switch will light up on its own as if someone pushed it. Once it's on, the only way to get it to turn off is to shut the car off. (On a side note, the entire time we've owned the car, when you purposely turn the rear defog on, the switch remains lit until you turn the car off. Meaning you can't turn the rear defog off when the window is clear, is this normal?) Also, while it's on, various idiot lights will come on. It's happened twice while I've been driving it. The first time, the "service" light came on, but then went off. The second time, the bulb failure light came on, though very dim, and continued to flicker. Any ideas? Thanks ahead of time, without you guys, I don't think I'd be able to own a Volvo and my wife loves it.

Sounds like the relay is having contact issues. That would explain the coming on all by itself and not shutting off. Suggest getting another relay and swapping it out as the most likely fix.

Regards,

Paul

not to override you, but these symptoms sound like classic 245 tailgate hinge wiring problems to me.

Just replaced both sides last spring. A broken tailgate wire would make the "service" come on?

A broken wire, especially the ground will do weird things. If it is the gtound the sleazy fix is to firm up the latch adjustment so that the gate grounds through the latch. Does your defroster come on when you hit a bump?
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09 V70, 03 Mini, 06 Camry, 10 Accent

"Does your defroster come on when you hit a bump?"

No, it doesn't seem too. I turned the car off at a stoplight, while still sitting at the light, it came back on.

Any idea where the relay is located?

Not much to say on the problem you have,but I have noticed the same problem with the phantom turning on the rear def. As far as I know the def has a timing device that turns it off after some time. You can't turn it off, it does it itself
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89 240 Wagon 217K, 94 940 185K