I have the original Toyota alarm on 91 T-bar, and I often find that when I unlock the driver door, the alarm goes off. I put of the alarm, but I have to shut the door again and lock - unlock the car several times before the imobiliser is reset. This is a pain in the neck, and wakes up neighbours if it's at night. Very embarrasing.
Anyone have any ideas?
I tend to get a few problems with the car, during and following winter, so I'm guessing in that time, heavy rain etc is getting into the electrics or something.
Which alarm unit is it, do you have a model number?
You say that your unlocking the driver's door, I presume with the key.
Don't you have a remote key fob to disable the alarm before you unlock the driver door?
IMOC - winners of JAE best overall club stand 2010, 2013, 2014 & 2017! 1994 GT-S T-Bar 397bhp with NOS *sold* 2016 Porsche Cayman 981GTS 347bhp Flat Six