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How To: Electric Fan 2 Speed w/ AC

Old 08-30-2011
06RangerXLT's Avatar
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How To: Electric Fan 2 Speed w/ AC

This is a quick How To on the basics of an E-Fan install. This is how i did mine, and its worked out great!

Feel free to add any info that could help people with this.

Also, i nor is this site, responsible for if you do this mod and something doesnt work or goes wrong. every truck is different, and you may have to improvise.

Now, Lets begin!

first off your going to need to remove your old fan:

as you can see, very little room before:

First thing to do is pull the intake:

Next, pull the fan and unbolt the shroud. (2 bolts on shroud)

i didnt have the tool to remove the bolt, so i took a big hammer and a chissle and hit the edge of the bolt, and it spun off my hand. 4.0 is regular thread, right tight left loose. 3.0 is backwards (right to losen) not sure what 4 Cyl is, sorry.

Tons of space now!

Had to make my own mounts, made out of stainless. probably 14 guage. get the fan where you want it, then setup how you want to mount it. MAKE SURE IT CLEARS EVERYTHING!!!

Waterpump clearence:
alow for atleast a half inch.

Now, you need to get a few things together.

1x Thermostat to turn on power at set temp. (get adjustable one)
2x relays ~ Dual Pole type 30A(get what the fan draws on high) I reccomend waterproof ones.
1x roll of 10 guage wire (power to fan and ground)
1x roll of 16 guage for signal wire
3x packs of female conectors 10 guage
2x pack of female conects 16 guage
1x pack butt connectors 10 guage
2x pack vampire clips 16 guage.
1x 30A inline fuse

remember, depending on the fan you use, these numbers and wire thinkness can change!

what you need to do is find a ignition power wire (on when key is on) for the T-Stat's power, so it can send power down the signal wire, to trip the relays. I used the wire that runs to my cig lighter, as its setup for ignition on off.

baiscally, the thermostat comes on with the truck. when it senses heat, at a certain temp it send power down the signal wire to one relay. that relay is grounded, so it activates the switch on the relay.

Power from the battery (with fuse inline) goes into #30. when power from the thermostat is sent to the relay, it goes through #85 and the to a ground plugged into #86. this activates a coil, which sends the power from the #30 to the #87(not "a") and into the fan. #87 is plugged into the fan high wire.

now, this is what turns the high speed on. works great cus you can adjust it on the T-Stat.

now, for low, you run a wire from the positive on the ac pump, to the second relay #85. be sure to run a ground for #86 in this relay as well.

now heres where the first relay comes back into play. Run a wire from the #87a on the first relay, to the #30 on the second relay. this will now give the second relay power when the first one is not activated by the T-Stat. Now, run a wire from the low speed on the fan, to 87(not "a") on the second relay. What this does, is cycles the slow speed with the AC pump.

why you do this:

you must have a fan going on the ac condensor when the ac is running.

this setup runs the slow speed on the ac cycle, but if the T-stat senses high temp, it will disconect the slow relay and run the high until the temp drops, then bringing the slow back on and running it with the ac. Note: it will only run with the ac if its on. if the ac is not on, it wont run slow speed. .

if done correctly, when you start the truck and trun the ac on, the slow will kick on. if the truck gets too hot, the high will bypass the low, cool it and then return power to the low speed relay. if the ac is off and the temp is below the setting, no power will be drawn.

if you got lost in that heres a simple wire setup:

#30 is power in
#85 is signal in
#86 is signal out (or ground)
#87 is power out when signal wire is powered
#87a is power out when signal wire is not powered.

now, 87 and 87a could be switched depending on what kind of relay you get. meaning the off plug could be 87a not 87.

if you look at a relay, theres 2 plugs going one way, and 3 going the other.

the two are power out. of the 3 going the opposite way, the ones across from eachother are signal, and the one alone is power in.

any questions email [email protected]
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How To: Electric Fan 2 Speed w/ AC-relay.jpg  
Old 09-01-2011
Alucard's Avatar
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here is all the info i have gathered for a mark VIII fan i plan on installing, but some of it should relate to other 2 speed fans as well

2 speed wiring diagram uses two temperature switches to control both speeds

wiring a spal pwm fan controller to a Mark VIII fan

another Mark VIII wiring diagram. uses two temp switches to activate the low and high speeds.

the pictures and info will help with identifying which Mark VIII fan you have.

also in addition to the 1 speed and 2 speed Mark VIII fans there is another single speed version that used varying voltage to change speed. these fans can be identified by that they have a white plug and no inspection port. the wire colors are BLUE(+) BLACK(+) and a third BLACK(-).

here is some info on them that i got off of a Mark VIII board.

The '93 Mark wiring harness contains three wires that plug into the fan. The blue wire is the power wire. The middle black wire terminates to nowhere inside the wiring harness. One questions why it is even there since it is not used.

The outside black wire is ground.

>The fan's power wire is one big blue wire, however, somewhere inside the wiring
>harness, that big blue wire splits into two smaller wires. Each of these smaller blue
>wires attaches to its own contact point on the VRCM.

>I assume that during fan low-speed operation that lower voltage is feeding the fan
>from just one contact point from the VRCM and that fan high-speed operation
>(.i.e. when the A/C is on) that extra voltage is now being added via the second contact
>point from the VRCM.

a post from pirate 4x4 on fan motor numbers

Single speed motor numbers.
93# F3LU-8K621-AA
97# F3LH-8K621-AB

2 Speed motor numbers I found off the net.
93-96# F3LY-8C607-A
The 93-96 spin 1100 rpms on low and 1850 on highspeed.

97# F7LZ-8C607-AB
98# F8LZ-8C607-AA
The 97-98 spin 1800 on low and 2225 on high.

two speed fan wires
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How To: Electric Fan 2 Speed w/ AC-320wire20colors20label.jpg  
Old 09-01-2011
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looks cool, but why?

if i read correctly, you used 2 heat sensors, 3 relays.


i just did the exact same thing, slow on ac and high that bypasses it, for half the cost.

for anybody who doesnt know, temp sensors are 60 each. relays about $8.

so without conectors or the fan, your looking at atleast $168.

i did this entire install for $135 INCLUDING the fan. i have a bypass switch to shut it off when crossing water, and when a speed is activated, i have a light letting me know. i even have a cutoff letting me know if power is lost from any positive wire.

its cool, but waaaayyy to much work for nothing. also, have you done the install yet? mines in a working.
Old 09-01-2011
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Location: Saxonburg, PA
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temp sensors and fan controls can be gotten from summit or even a local parts store (i was at an advanced auto two days ago and saw kits from $30 to $50 each) for around $30 each i have no idea where you get $60 each.

theres nothing wrong with yours if it works for you then great im glad it works. at the beginning of your first post you said to post any info that might help others so thats what i did. alot of the Mark VIII fan info is scattered accross the internet and it took me a long time to get all it together.

most of my info is geared towards the Mark VIII fan that draws a lot of amps on the high speed and has a large amp spike when it starts up. thats why two relays on the one diagram are needed for the high speed.

i haven't installed mine yet i still need to pick up a fan and a few other odds and ends.

i have already built the one that takes 4 relays minus the temp sensors i have i think around $60 in relays wire and connectors in it. i think it may have taken about an hour to build it.
Old 09-01-2011
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Nice ikea work light (desk light) i have the same one
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Old 03-05-2012
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well everything was great, but i lost power. turns out water got into the relays and rust plus 30 amps means the coroded fast. needless to say, i have new 30/40 amp relays that are waterproof, and will do a write up on the rewiring. I am going to step down a guage in wire also, from 10 to 12. 10 is a bit too stiff to get it into small spots. Gonna make it all look fantastic.

need to soldier the AC pump connection, mount the relays on the firewall away from moisture, and clean up under the hood. Just removed my Aux lights and the relay also, as i dont want them on the truck anymore.

stay tuned for more pictures here and in my build thread.

i know how we all love the pics.
Old 10-15-2017
MaDMaXX's Avatar
Join Date: Jul 2017
Location: Oregon
Posts: 781
Any more updates on this?

What fan did you pick up for it?
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