speedster93b
+1y
the way the relay works is one side is powered or the other. not both. you'll need another relay.
the 85 and 86 terminals are the low side power and ground(you'd wire your toggle switch, pressure switch etc on this side) and the 30 and 87 and 87a are the high side terminals (for wiring a fan, lights, compressor, anything with a large draw that needs a switch)
when there's no power to the 85 or 86 terminal, there is a switch inside the relay that is open on a 4 prong relay, and its at the 87a terminal on a 5 prong relay. that'll be constant power.
as soon as you apply power and ground to the 85 and 86 terminals there's a coil that acts as a magnet and 'switches' the switch from the 87a to the 87 terminal.