Quick way to get the aux fan running again?

#1

the fan in the front of the radiator is my only fan now. had to pull off the mechanical fan as there was a problem with the clutch. the electric fan used to come on with the fog light switch, but the guy doing my cage ripped that wire out and now i can’t find it. i have another switch available to me that i “borrowed” from work that should do just fine even without the relay. how to i wire this in tonight so i have a fan this week at the track?

#2

Fan should have 3 wires, Ground, Low Speed, & High Speed. Use the multimeter to figure out which of the 3 is the Ground. Then run a 12V test lead to the other two wires to figure out which one is High Speed.

Then run a line from the battery connector (right-front of engine bay on firewall) to your switch and then from switch to High Speed wire.

We’re talking about 30A here. I think that you should use a relay.

#3

thanks for the explanation! i see what i can do.

i do have a switch rated foe 30A though, still need a relay?

#4

OriginalSterm wrote:

[quote]thanks for the explanation! i see what i can do.

i do have a switch rated for 30A though, still need a relay?[/quote]

I would use a relay. For me that’s too much current to put thru a switch. You can put a relay near the fan and then you can get away without a fuse. Since it’s a short simple run of wire it’s less likely to have a problem that would need a fuse.

But a longer run that goes thru a switch definately needs a fuse. For a while I had a 30A line going to my gauge panel for gauges, and switches to Traqmate, ChaseCam, Coolshirt and fan. The 30A fuse kept blowing. That’s when I stepped back and realized I’d been dumb to attempt to bring all the fan amperage to the dashboard and wired the fan in with a relay in the engine compartment.

It’s not just a matter of whether or not the switch is rated for the current. High current loads like short simple cable runs.

#5

can you draw a diagram. I’ve been thinking about adding a lighter fan

#6

See schematic in the pdf

I wrote this for someone a couple weeks ago:

Pretty much any ol’ 12v relay will work, you just have to figure out the relay’s “pin out”. I don’t know how much you’ve played with electronics so
don’t let me patronize you…A relay is just a “remote” switch. It allows you to control a high current circuit but only run a small current thru the dashboard switch

In the absence of a relay you’d have to use some big-ass switch that could handle all the current. The relay lets you use a little switch.

Think of the low current side of the relay as the “switch” side and the High current side as the “switched” side. When you throw the little dashboard switch, it applies 12V to the relay. That closes the connection on the high current"switched" side and then fan then gets 12v.

If your relay isn’t labeled, then use a multimeter and figure out which pins seem to do what. It needs to be a 4 pin relay tho, otherwise the pin-out
will be too hard to figure out. The “switch” side will have almost no resistance so figure those two out first. Then the other two pins are the high current “switched” pins. That’s all you need to know to use the relay.

But test it a couple times by…
With no voltage on low current switch pins, high current switched pins should be near infinite resistance.
Put 12v on switch pins and high current switched pins should be near 0 resistance. [file name=20090817095220299.pdf size=47791]http://spece30.com/media/kunena/attachments/legacy/files/20090817095220299.pdf[/file]

#7

Why not just use the fan relay already in the car? There are two.

Only have to bring the ground side of the relay to the switch and ground it to turn on the fan.

#8

The fan will kick on by the temp sensor in the radiator when the car gets hot anyways. Why even worry about a switch?

#9

My switch is bad. Fan doesn’t come on at all, even with the proper pins in the switch connector are grounded. The relay is fine, the motor is fine, I just need the fan to come on.