Electric Fan How-To – courtesy of Hotwire

(Focusing on late model Chevrolet S-10)

Introduction

This is a quick "how to" on installing an electric fan be it store bought or junkyard bound. This document focuses on installation on 97-98 4.3 motors but can be applied to any motor vehicle. All statements included in this document are based on experience and are the views of the author. This is purely made for referencing and is not a complete step by step manual or advertisement for any certain product or procedure.

** If you do buy a fan from a junkyard be sure to find out what size fuse is associated with that fan to avoid under powering the fan or having the potential for electrical fires. Be sure to take note of the gauge of wire being used to power the fan. Be sure to get the wiring harness with as much wire attached to it from the donor vehicle as possible. Make seller connect the fan to a battery or other 12-volt source to assure proper operation, and try to get at least a 30-day warranty. Check for good bearing operation in the fan by rotating blades by hand and listening closely to motor assembly. Fan should be completely intact with no chips, breaks, or worn parts on the fan blade itself. These things turn at high rpm and even a little nick can cause big problems. **

Parts / General Information

Here’s a list of things you will most likely need:

(I have stated max length on wires; it’s always better to have too much, rather than not enough)

First start out by removing the top fan shroud and stock clutch fan. On the late model S-10s, clutch fan removal is pretty interesting. Sometimes you can rent a removal tool from an auto parts store, or get creative. I found one way to do it is to brace a wrench (13mm / ½") across two of the bolts on the water pump pulley, open end around one bolt, handle leveraged across another. Then use a big pair of channel locks or adjustable wrench to remove the large nut. This is not the correct way and I don’t really recommend it. Besides possible over torquing of water pump pulley bolts, it’s hell on your knuckles.

 

 

Schematic

Fan Positioning

Take your efan and test fit its position in the truck. Make sure you have enough clearance to run wires and avoid all pulleys and belt when engine torques.

I used a single speed efan out of a wrecked ford Taurus. The shroud was modified w/ a jigsaw and coarse wood bit. It was mounted so that it was offset to the driver’s side w/ little clearance between it and the stock water pump pulley. I had to get a little creative w/ a jig saw to make it fit, but it slides right in and provides ample cooling, especially being right where the output hose comes into the radiator. The Taurus fan shroud is covering approximately 2/3 of the radiator cooling fins. The dual speed fan has a pancake style motor, requires less sawing and can be mounted straight up on the radiator.

FIGURE 1: Clearance on 97 w/ Single speed Ford Taurus Fan

FIGURE 2: Clearance on 98 w/ Dual speed Ford Taurus Fan

The fans were positioned till snug against the bottom shroud. I inserted about 4 self tapping screws through the top lip of the Taurus shroud and into the top aluminum brace that runs along the top of the radiator, then pulled it tight against the radiator with the factory fan shroud. A foam gasket installed on the fan shroud (to keep it from rubbing the radiator too much and to provide a good seal) is optional, but it seems to be doing fine without.

 

Functional Wiring

The next step is to get the wiring in order. You will have to determine the best spot to tie in your power and accessory wires. I have found the best places for my application, but yours may vary from what I list.

On my 97 I ran the +12v switched power off of the egr valve motor, it’s a pink wire. Just have someone crank the key on and off and search for something getting power only when the key is in the on position. Then use one of the blue crimp splicers and tie into that line. Since it was out in the open I wrapped it up w/ electrical tape to conceal it and retain factory appearance.

FIGURE 3: EGR splice, located in factory loom, hidden w/ electrical tape. (97 S-10 4.3)

Next is the A/C line if your truck came equipped. I just pulled the power plug off the rear of the compressor, had someone turn the A/C on and off w/ the key in the ON position and probed the end of the harness for +12V (two-wire plug, round, back of compressor under intake hose). I then traced the line back to a hidden spot in the wire loom and installed another splicer, on my 97 it was light green:

FIGURE 4: A/C Line Splice located behind Throttle Body hidden in factory loom

FIGURE 5: A/C power connector, located on rear of compressor, under intake hose

I ran the wires inside the factory wire loom as far as I could to conceal them and keep the engine compartment looking clean. I used either electrical tape or black wire ties to retain the wires where the factory wire loom wasn’t accessible. Both wires were then run out beside the alternator with 3/8" wire loom to bring them up beside the battery.

Note: Somewhere on AC line you have to install a diode inline to keep the thermostat from turning on your ac compressor. I used a 1N4007, it’s cheap, will hold the load of both relay coils and can be found anywhere.

Think of a diode as an electrical one way street. The end w/ the silver band going around it is the exit. In this example, the band is closer to the fans. If you look at FIGURE 3, you will see some Carolina blue heat shrink about 4 in below my hand. This is where I located my diode. It was a nice easy spot to get at, will not be tampered with and is not at risk of breaking. I just stripped the wire, wrapped it around the diode’s leads and soldered it on there (WITH SILVER BAND CLOSEST TO RAD!).

Power Wiring and Placement

OK, now we got the functional wiring out of the way and have them both down by where we are going to mount the relays (near battery). Please refer to the schematic at the top of the page for wiring of the relays. I have included some pictures of two setups. It’s not the cleanest install, but it was inexpensive and works exceptionally well. The pic of the 98 install took a little more time and patience and looks better when the relays are seated properly against the factory fan shroud.

 

FIGURES 6 and 7: 97 Relay Jumble; 98 Relay Jumble

 

FIGURES 8 and 9: Mounted to Taurus shroud (97); Mounted to factory shroud, pass side (98)

FIGURE 10: Items visible: makeshift 50 amp foreign fuse, top of relays, and battery tap.

Misc. Notes

The double relays are necessary unless you have a fan that uses less than 30 amps, or if you can find a larger current relay for 12V applications. I chose these for ease of replacement and price.

I found a 70 amp relay @ JCWhitney for $10. I will try and get the layout of the relay from them so I can post an alternate schematic.
http://www.jcwhitney.com/product.jhtml?CATID=50489&BQ=jcw2

Accessory relay wiring harnesses can be used, but cost more. They do clean up installation however.

Wiring to foreign fuse was done using two male spade connectors pushed into terminals.

Both temp sensors for thermostats were installed in radiator fins approximately 3"x3" away from upper driver’s side corner of cooling fins, near top radiator hose inlet. The 98’s probe is just wrapped around the factory shroud, bent in wide arcs to prevent kinking and to avoid any rubbing. The 97’s is run along the topside of the Taurus shroud, encased in split vacuum tube to resist rubbing.

Power from battery on 98 was using factory side terminal w/ accessory nut replacing 5/16 lug. 97’s power tap came from dual post battery w/ marine quick connect terminal.

On the 98 dual speed fan, brown w/ yellow = High speed, brown w/ orange = Low speed.

When running wires to fan, be sure to wire tie to fan shroud to reduce risk of wires making contact w/ fan or fan belt.

Both fan and relay grounds were run to frame of truck via holes in bottom of bottom fan shroud.

Power wires for fans can be routed around fan shroud, or routed through bottom shroud by cutting or drilling a hole in the plastic. If running wires through, I would suggest running them through the bottom shroud to reduce the necessity of having to remove wires when removing the upper shroud.

 

Coming soon… specifics (pictures, info) for the popular Flex-a-Lite BlackMagic #60 install.