John-
Most electric fan kits include a relay. This is because the amps
required to run the fan might place an overload on any existing circuit
you might add the fan to. At one point, rubber bumper "B's" had the fans
wired on the constant power fuse,using a thermo switch, but the problems
of an operating fan in an unattended car outweighed any advantage, & the
wiring was changed so that the fans would only run when the ignition was
on.
If your fan did not come with a relay or some sort of thermo switch or
"fan stat", I suggest you purchase both.
In my car, I run a wire from the fuse box, fused side, to a fan stat, an
adjustable thermo switch, that controls when the fan comes on. From the
other terminal of the fan stat, the wire goes to a relay, this would be
"W-1" on a Lucas relay, or "85" on a Bosch or Hella relay. I run a #12
wire from the battery terminal on the starter to the "C-1" terminal or
#30, on the relay. From the "C-2" or #87 terminal, run more of the #12
wire to the fan. The other fan wire should go to a good ground, such as
one of the radiator mounting bolts. It too, should be a large wire, as
it carries as much electricity as the + wire. One additional wire needs
to go from the relay terminal "W-2" or #86, to ground. This can be a
small wire, #18.
If you wish, you can substitute a switch mounted in a convenient
location, instead of the fan-stat, but this requires watching the temp
gauge & remembering to turn the fan on & off.
A good quality Hella relay to use is #4RA003 510-082, 12V, normally
open, or you can use a duplicate of the Lucas relay now in your car.
If you need more info, e-mail me off list. If you need a technical
explanation, hope you get a reply from someone smarter.
Jim
2V8's, no dollars or sense
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