E-Fan upgrade -- Complete!

Hey all...as the title suggests, I have finally completed my e-fan upgrade!

How I did it is a bit different, however, because I tied my e-fan wiring into my heater control assembly, since my A/C is basically non-existant.

What I did might work for you, if you don't mind not having A/C.

This is what I did:

First, research:

I had attempted to use an aftermarket thermostat controller, but it did not turn on the fan unless the control knob was in one position. So, this was a no-go, as I would do better with having a switch that is already installed that has no function. After looking at the 4.0 wiring diagram, and comparing wire colors, I discovered that in 1992, Ford put the same wiring diagram on all trucks (same wire colors).

So, after figuring out which relay was the A/C WOT cut-off relay (it's the black relay, part of the relay array under the Power Distribution Box, located on the passenger side of the engine bay: The green relay is the fuel pump relay, and the brown relay is the EEC relay), I disconnected the connector the relay traced back to and the two-wire connector on the pressure tank for the A/C system. Once this was done, I pulled out the relay and it's harness after unbolting and removing the system ground (this is located just behind the Power Distribution Box on the fender).

Next, I tested the purple wire at the connector I disconnected. This wire, if it has continuity, goes back to the fan control switch on the heater control assembly -- to close this circuit, press the fan switch in, as though you're turning on the A/C. This circuit should have battery voltage (note: As this is an ignition-switched source, the key must be on and the battery must be connected for this check.). Push the fan switch again, turning the A/C off (the indicator light should go off). Your DVOM or multimeter should read 0v or close to it.

This wire is the power source for my e-fan's relay to turn the fan on when needed.

For the relay side of the disconnected harness, remove the red plastic piece over the harness plug. Using a small, flathead jeweler's screwdriver. Pop the dark green wire out of the connector. Replace the red plastic piece in that connector. For the relay side of the harness, take the red piece off the relay connector. Using the screwdriver again, remove the red and pink wires. You'll short these together. Take a pair of wire cutters and cut the purple wire at the two-wire connector (this goes to the clutch pressure switch, by the way). You are now ready to strip and connect the wires for your relay-controlled e-fan.


On a 4-pin relay, wire the fan and the activating power and ground as follows:

Power wire, relay coil: Connect to Pin 85. (This is the purple wire.)
Ground wire, relay coil: Pin 86 at the relay, ground to the fender at the same location as the removed A/C ground.
Fan power wire, incoming power: Pin 30 at the relay, and directly to the battery positive ( + ) terminal.
Fan power wire, outgoing power: Pin 87 at the relay, and connect this wire to the positive side of the fan motor.
Fan ground: Connect this to a good known body ground.

To test this setup, turn the ignition on (but do not start). If done correctly, the fan should come on.

Note: I only used a single speed fan for this out of a Chevy Celebrity station wagon. To wire in dual fans will require some varience on this setup.

Also, as this is a relay-controlled circuit, when the circuit is off, you do not need feedback diodes, as this setup is nonfunctional when the relay is open.

Having a manually switched fan is just asking for trouble. Sooner or later you'll get lazy and forget to keep an eye on your temp gauge constantly, and overheat because you didn't push the button to turn it on.

Fix, replace, or figure out the thermostat switch so that the fan will turn on and off when it should, whether you're paying attention or not.

Using the WOT relay is fine if AC is not needed, but you are only saving under $10 for relay and base.

But very good write up and inventive solution.

And I have to agree about the manual ON/OFF switch, anytime you involve a human in a critical circuit you have a "when failure" not an "if"

4.0l can be overheated ONE TIME and you have a cracked head, flaw in head castings for that model.
So cooling is a critical system.
Just having the fan relay activated by key On circuit would be a better solution than an ON/OFF switch, but temp Switch, not sensor/sender, would be best overall.

Adjustable temp sensors are for climate control in your house or cab, lol
For radiator cooling fan control you just want a temp switch, 185degF, placed on upper rad hose on Rangers.
Thermostat opens at 190degF, so fan would be on when coolant is flowing thru rad, only time it is needed.

I have a thermostat switch controlling a generic four post relay... works great.

Is your fan going to shut off at WOT?

85_Ranger, no, my fan does not shut off at WOT. The WOT relay was the factory relay to cut out the A/C at WOT. If on, my fan stays on, no matter engine RPM. I mentioned the WOT relay because I used the power wire for it as the power wire for my fan's relay coil.

As for the other concerns, my engine is a 2.3...so cast iron head and block.

As for not paying attention, I'm too OCD not to. I am always monitoring everything when I'm on the road.

By the way, I have some information for an intermittent charge light on the early Rangers: Check the Black/white wire on the alternator, and make sure it is tight. For the longest time, my charge light would come on and go off, seemingly on it's own -- the problem was a loose wire at the alternator. Since fixing that, my charge light has not come on once.

So you did not actually use the WOT relay as your fan relay?

No. I got an aftermarket 4-pin relay at Advance Auto.

By the way, I have already installed a bung used by a JY Ranger's ECT, and mounted a temperature sender in it. Once I can acquire a setup that can use that sender, I will add it in (money, not availability, is the issue right now).