Looking at online stuff for the fan relays labeled "AC" in the under hood fuse box, all schematics show the spade terminals in a row from left to right. However, the actual relays have 2 spades top, 2 bottom. 2 are silver, 2 are copper colored. Using a 9v house battery, I can get the relay to click on/off, so can at least figure trigger out. However, I don't know if polarities need observed on relays? I know one of the spades would be ground, but does it matter which?

I'm swapping a radiator fan from my '95 Legacy into an '82 S-10 (2.8L manual trans w/ mechanical fan getting deleted) until an eventual mid 90's Vette 350 w/man. trans and better cooling fans, etc. get swapped. Truck is still carb'd so everything needs to remain mechanical for the time being.

 

Polarity doesn't matter on the load side (contact closure) of a relay.  Polarity does matter on the control side as some relays have a diode to suppress the back EMF when the control side opens.  

Thank you for that as now I'll be careful with the trigger.

 

Ended up harvesting the entire harness from fan motors to the relay block. For anyone stumbling on this in the future; if you separate the plastic backing covering the wires on the relay block bottom, you can follow the 10 amp fuse wire to each trigger as that should be the 12v+ (brown wire). The 20 amp is the fan power. The entire relay block separates from the fuse holder block and can be mounted separately if interested in doing a fan transplant into something else. Separately, there is also a 45 amp larger fuse (red base, clear window on top) upstream of the 20 amp fuse. Can actually transplant the entire fan assembly including the harness and relays easily enough.

Using just the main 5 blade fan, powering one relay at a time = low speed. Apparently, both by themselves = slow speed i.e. one OR the other. Triggering both at the same time = high speed. Reminds me of a DVC speaker where each coil is separate and can play independently or combined for more power.