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Old 08-02-2011, 09:21 PM   #1
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Crunch Time - Wiring Question

I'm trying to get my e-fan installed before this saturday to hopefully shame some kids at work at the track.
I have a couple questions:

does anybody have a p/n for a short belt?

Can someone give me a better rundown than the **** google searches i've been coming on for how to wire the Mark vIII fan properly.. i have the adjustable kit and two 80amp relays and i want to put the highspeed on a flip switch. (i read something about a diode for when you shut the fan off too)

any other ideas?

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Old 08-03-2011, 12:30 AM   #2
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Crunch Time - Wiring Question

Why the short belt?

Not too familiar with the two speed fans, but I think most are setting them up to use one speed only. I think I remember seeing a diagram on one of the other forums to do what you want. I am pretty sure you need to have the high speed relay deactivate the low speed relay and power the high speed wire at the same time- you can't have power to both low and high speed wires at the same time. Don't know about a diode.
here is what I ended up with. Good luck!
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Old 08-03-2011, 12:49 AM   #3
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Crunch Time - Wiring Question

Kenson- one diagram I had seen before. I think the two speed one is what you want, but you use your switch in place of the high temp sensor.

Also, you can ignore any connections to AC compressor- your truck should have a dedicated efan for the AC condenser. Most vehicles don't, so they turn the fan on whenever the AC runs.

What kind of controller did you get for the low speed? They might have info on wiring also.
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Old 08-03-2011, 12:14 PM   #4
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Crunch Time - Wiring Question

This is the setup I was going to use to run either the hi or low side of my viper fan before I got the DCControl unit.

You really only need to wire one side, either speed should be enough to keep you cool.

This diagram uses the adjustable controler you can get at almost any part store and a 75a relay.
You can ignore the ac wire or use it with a switch for a manual overide.
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Old 08-04-2011, 06:02 PM   #5
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Crunch Time - Wiring Question

thanks for the responses
I was hoping that the short belt would get rid of anything i don't need to go straight (i.e. powers steering and a/c) I'll look at the belt routing tonight and see if i can figure anything out.
Newblue you were right about not being able to run voltage to high and low speed at the same time.. i'm just trying to figure out how to wire it. Low speed is good enough for everyday use but i would like to be able to use high speed, toggled by a manual switch.
I might go see if autozone has a rocker switch that way when i switch over to high it takes power from the low speed relay.. I would imagine that would work
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Old 08-04-2011, 07:37 PM   #6
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Crunch Time - Wiring Question

Kenson- here's a mess of images for 2 speed fan wiring. Most come from forums so you can read a little background.

You should be able to make a switch turn off one relay and turn on the other, but most of these diagrams show using one relay to turn off the other. Seems simpler.

Note Bill_L's diagram- he is using the 40 amp relay built into an Imperial single speed fan controller (30 amp rating) to turn on a 75 amp relay. This way you can get a cheap controller to run a high amp fan like the Taurus. What controller are you using?

Also- everywhere you see +12V battery, +12VDC source, ignition controlled +12VDC source, etc. on a diagram, make sure you are fusing that wire as soon as you tap from the source. There should be no wire you run that is not protected by a fuse or circuit breaker. Helps prevent Ram fires!
Cool on the belt, I wanted to make sure you were still turning the water pump!
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Old 08-04-2011, 08:28 PM   #7
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Crunch Time - Wiring Question

short belt part number - 538k6

parts list for fan install -
80A fuse to both relays
30A fuse to flip switch and fan controller hot(unless you are running that through the 5 pin relay.. see below)
bosch 5 pin "changeover" relay (only needs to be enough amps to actuate the 80a relays)
10 gage wire - power wires to and from 80A relays
12/14 gage wire - signal wires, fan controller, from flip switch to 5 pin relay
solder - weather tight connections!
heat shrink - same reason
1n5408 diode - a good idea
universal (preferably adjustable) fan controller... does not have to be able to handle high amperage, just enough to actuate the 80a relays and there shouldn't be any that can't
two 80Amp or more relays (found on amazon for 15 plus shipping)

-install fan and controller as instructed however do not worry about the ignition lead for the controller yet, just hook up the constants and send the "Fan Pos+" connection to one of the 80a relays. (if there is no specific ignition lead on the fan controller, just a hot and a ground then use the power wire)
-wire the 80a relay that is to the fan controller to the fan low speed (should be the middle terminal)
-wire the other 80a relay to the high speed side
-ground the remaining terminal
**do not use spade connectors, they are not meant to carry this much amperage unless specifically stated
-hook up 5 pin relay as follows
30 = constant [positive (+)] power (usually wired directly to car battery)
-85 = coil ground (wired to the negative (-) battery terminal or any grounded metal panel in the car)
-86 = Manual switch to toggle high speed fan
-87 = To 80Amp relay that controls HIGH speed circuit
-87a = to the ignition lead/hot wire for the fan controller

lastly just wire the 1n5408 diode from the negative to the positive (DEFINATELY NOT THE OTHER WAY AROUND LOL) on the fan. Doubt it will hurt the big relays but it wont do them any favors either.
The diagram that bill posted above shows what i mean

I believe that will do it.. any other ideas/corrections?
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Old 08-04-2011, 11:02 PM   #8
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Crunch Time - Wiring Question

Sounds like you"re all over this. Note that you need at least one SPDT single pole double throw relay for one relay to control the other. Most I see in auto stores are SPST (no 87a terminal). One of each is wired like this.. In this diagram, "complete the circuit from AC clutch" would be +12 volts coming from your high speed switch, and "adjustable thermostat switch" would be the entire cheapo fan controller.

This is a way to do it with two SPDT relays. Here "temp probe switch" would be your cheap fan controller, and skip the "To AC compressor Line but use the switch as shown.

Diode- On your fan there are two positives, might need two diodes? From what I understand, the diode blocks negative voltage 'generated' by the turning fan as it is coasting after power is cut. I am not sure how this works.

I initially set mine up with the controller always on, but the fan ran 2 or 3 times after the ignition was shut off, so I changed it to ignition switched power to the controller.

Good luck!
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Old 08-05-2011, 01:34 PM   #9
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Crunch Time - Wiring Question

short belt is good for a tenth at least in the 1/4 mile. I run one every time I go to the track.

p/n: 537K6 or if too short 538k6
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Old 08-05-2011, 05:27 PM   #10
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Crunch Time - Wiring Question

newblue - yea, i couldn't find diagrams so thats why i did the write up.. thanks for posting those, I know that will make it much easier for someone later.
Loredo - all they had at the parts store was the 537 so hopefully its long enough.. that water pump isn't getting much love is it? lol
One thing the part store did have was the pigtail for the fan, comes with a nice oem plug and 10 awg wire leads... perfect.. manufacturer is "handy pack"
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