Re: Carputer 101
Well you are sort of correct.
Pins 85 and 86 are used to power the coil inside the relay. One will be negative and one will be positive, since my alarm sent out a negative signal from the trigger to pin 86, I needed a positive signal going into 85. It is very common for alarms to have a negative trigger. Like I said a multimeter is your friend for this type of installation.
However...if your relay has an internal spike suppression diode (this is not usually the case), then pin 85 must always be negative and 86 must always be positive since diodes only allow current to run in one direction.
References : chaunb3400, Team H&K, diminishedpower, pickup1, sublime06, sporty_drew, JRock10, Jando86, sundownz