Where does the red wire connects to?

The red wire connects to pin 87a which remains in contact with the common (pin 30, blue) when the relay isn't energized. this is known as the "Normally closed" (NC) circuit. Don't use it unless you want the relay to power something off when the relay activates; i.e., for most operations you leave it disconnected.

What gauge are the leads that come off the relay?

The wire on these harnesses are 16AWG and are too small for powering vehicles electric fan on radiator which pulls 15-30A per fan. Use a 30A fuse right after the battery going to the 85/86 on relay, make sure the 30 & 87 on relay have 10ga OFC primary wire. You need 10AWG guage for 7-16ft applications, it has to be OFC/Tinned Copper, make sure it's not CCA. GS Power brand on Amazon has OFC called 100% pure copper. Pick up yellow(12-10 guage) heatshrink butt connectors(to connect the wires properly), yellow heatshrink female spade connectors(for relay post prongs) and some yellow heatshrink ring connectors in multipack of different ring diameters(for grounding the wire to Frame bolts) Then get heatshrink tubing 1/4" should be fine if it's 3:1 or 4:1 Wirefy is a good brand. I get the spools instead of the precut packs. Heatshrink connectors and durable heatshrink tubing is extreamly important for automotive purpose, the weather in vehicles can corrode it and cause melting or worse.

Will these work to shut off compressors for air ride suspension on a truck

As long as the total amperage draw of the compressor and any other power consuming components of the air suspension system are less then the 40 amp relay, these should work fine.

Im more of an ac instead of dc guy but u can run 24v through ur no terminal just has to have 12v to bring in the coil on the relay correct?

You can apply 12VDC to the coil (usually, that means 10 -15VDC) to close the contacts of the Normally Open terminals. When the Normally Open terminals are closed, the Normally Closed terminals are open.Once the terminals are closed, they can handle 30 amps DC.There isn't a specification for the voltage that the N/O and N/C terminals can handle... but I'm certain that they can handle 24 volts.Just don't put more than 14.4VDC across the coil.

ASIN	B017VDI0GY
Best Sellers Rank	564,814 in Automotive ( See Top 100 in Automotive ) 2,223 in Car Relays
Brand	EPAUTO
Coil Voltage	12 Volts
Connector Type	Plug-In
Connector type	Plug-In
Contact Current Rating	40 Amps
Contact Material	Silver
Contact Type	Normally Closed
Contact material	Silver
Contact type	Normally Closed
Current Rating	40 Amps
Current rating	40 Amps
Customer Reviews	4.7 out of 5 stars 6,576 Reviews
Item height	3.61 inches
Manufacturer	EPAuto
Maximum Switching Current	30 Amps
Minimum Switching Voltage	12 Volts (DC)
Mounting Type	Socket Mount
Mounting type	Socket Mount
Operating Time	0.01 Seconds
Operation Mode	Automatic
Specification Met	epauto
UPC	690443852320
Upper Temperature Rating	125 Degrees Celsius
Wattage	560 watts

EPAuto 5 Pack - 30/40 AMP Relay Harness Spdt 12V Bosch Style

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