Diode & Pin Switch Question

Question: I've installed 2 negative trigger pin switches on 2 doors. Both are tied into the single Green Negative input on the brain. When both doors are closed and the alarm is armed, opening either door triggers the alarm. If 1 of the 2 doors is open when the alarm is armed, opening the other will not trigger the alarm. So, here's my diode question: Does using a diode on each pin switch isolate each door? Meaning--If I arm the alarm and one door is open, is the closed door supposed to be in an armed state that will trigger the alarm if opened? I tried using a 4100 diode on each switch (cathode on the switch side) and the results are the same. I've read a lot here, so I'm just not sure if I'm understaning the use of diodes correctly. Thanks in advance.

The diodes are needed only if the existing setup is wired so that opening one door does something different than the other door. Driver side door usually has a separate line so it can detect a key in ignition condition with the car door opening, where the passenger side doesn't, and may only turn on the courtesy lights. As far as your alarm is concerned, opening either of the doors will be the same as if you had both open, since that green trigger line will be grounded either way. If you want them to act independently, you have to wire the second door to a separate trigger input, so the alarm won't bypass the trigger when you arm it with one of the doors open.

Excellent. Thanks for the explanation. I thought the diode isolated one pin switch from the other while connected to a single input.