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Old 05-21-2013, 11:17 PM   #8
Tally HB
The Old Guy
Join Date: Feb 2013
Location: North Florida
Age: 57
Posts: 721
Vehicle: 1989 D21 Base 2WD 2.4L
Thanks: 23
Thanked 100 Times in 80 Posts

So I have the below pictured wiring set up for now

If you don't understand how a relay works there are several videos on youtube that fully explain how they work.

They basically separate two voltage sources so that higher voltage does not run through the control switch.

The control switch uses low amperage voltage, ran through the switch, to trigger the relay coil to pass high amp voltage to the accessory you are running. That is why you use small gauge wiring on the switch side and large gauge wiring on the accessory side of the relay. Large wire carries higher voltage better and with less chance of over heating the wire.

However, a relay itself can be substandard or not up to the task. Some relays will not stand up to constant duty (constant running), or the higher voltage needs of high speed operation and fan startup, so you need heavier duty relays to do these kinds of chores.

Typical automotive 30, 40 or even 50 amp relays are fine for fans that are temperature controlled and do not constantly run and are not running on high speed.
1989 D21 Standard Cab 4x2
2.4L Z24i, 5spd

Last edited by Tally HB; 05-28-2013 at 10:48 PM.
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