1997 Volvo 850 - ELVAT8C-PROOE2 OEM Keyless FOB...

[xHeart]

That doesn't look like the factory-fitted alarm system – the fobs and alarm horn look different, and the factory system doesn't have the switch by the hood release, or the pin that you mentioned. The alarm horn nut mentioned is probably not relevant in your case.

The 'sensor' is the unused connector for the factory alarm horn. The pin is there to trigger the alarm if somebody tries to open the hood (the factory system has a sensor in the hood latch instead). The switch by the hood release is probably something to do with disabling or resetting the alarm. Years ago, I had a car with an aftermarket alarm, and it had a hidden switch that (I think) would let you disarm the alarm if the fob stopped working.

You are right.
There is nothing at sensor connector.
I can hear a faint sound only when the alarm is triggered.

[xHeart]

Subzero temp.
Leaving driver door unlocked to avoid morning unlocking with key, but it starts at first crank -- awesome.
I will pull it in our heated garage this weekend to look closely at the valet switch, and take next step with Ozark's tip for ignition ON.

Not all male drivers are ------------------------------------ when weather gets nasty.