electric radiator fans

Flex-a-Lite claims 17 HP and 20 ft. lbs. power gains at the wheels (the Ford version vendors make similar claims).  The real numbers are reported to be closer to 10-11 rwHP.  According to one user, consecutive dyno pulls (rwHP) showed 357 (with),  369 (without), 358 (with), 367 (without).

Installing a 170° thermostat (Stant part # 13967) at the same time can provide additional performance gains.  Stock is 180°, but most have reported that it is really closer to 190.  JDM recommends 170° as the lowest thermostat.  The logic is that the 160 can cause the PCM to keep the truck in the "cold warm-up" mode, preventing the truck from even running in closed loop mode at cruise.  This causes the engine to run too rich.  However, several Lightning owners have reported 4 or more HP using the 160 over the 170.  You make the call.

Electric fans allow the use of a manual switch to keep the fans running full time when racing.  While this will only cool the water in the radiator unless the engine is running, it may may the runs more consistent.

You may want to replace the stock water pump, as it has a shaft for the mechanical fan that is now sticking out for no reason.  Info on replacement pumps is here.  I used a Navigator pump (same as 03-04 Lightnings).

The Flex-a-Lite controllers are notoriously unreliable.  I used a DC Controls unit instead.  First, I fabbed a plate for the control.  The fuse is from the Flex-A-Lite kit.

Next, I fabbed a plate to cover the main power connections on the fender well below (see photo above).

Fan prep:  The instructions do not even make it clear whether the fans are to be wired in series or parallel.  The below image should help.  Note that the black wires are hot and the blue wires are ground.  1/2" corrugated wire wrap will just fit through a 1/2" hole in the shroud.  I filed a channel in the divider piece so that the wires would not fall against the hot radiator fins.

I used TechFlex braided fiberglass wire covering for most of the other wire runs.  This product is very similar to the braided covering on the intercooler fluid hoses under the radiator.  TechFlex can be bought online at Pacific Radio.

Wiring:  There are really only three connections to the truck's electrical system.

The main power can be connected to the starter solenoid or directly to the hot lead of the battery.

photos courtesy of JDM

2.  The key on sense and can be connected with a relay tap (included in the fan kit) to the terminal in the fuse block shown below.   The fuse box is located in the engine compartment in the corner nearest to the driver.

3.  The a/c on sense can be connected with a spade lug to the location in the fuse block shown below.  It is reported that the fuse block can be removed from the housing and the connections made from below for a cleaner install.

photo courtesy of JDM

For the DC Control controller, the correct A/C tap is not the one shown.  It uses the middle of the three blades towards the rear of the relay shown.

A neater method of wiring is to go in from under the fuse block.  To do this, you need to pull the block up (retaining tabs highlighted in yellow below), then remove the lower cover (shown to the right).  You can then tap directly into the wires.

The photo below shows the wires going to the ignition, A/C sense, and temp sensor.

Fan removal:  I bought some cheapo ($20) wrenches from Pep Boys made specifically for removal of Ford fan clutches:

Follow the instructions in the service manual.

The shroud is almost impossible to install per Flex-A-Lite's instructions, which are to mount the radiator brackets first, then attach the fan to that.  Impossible.  There is no room to install the bracket-to-bracket screws with the fan in place.

Even the buttonhead allen screws that they supply are worthless.  There is no way to get an allen key on the lower bolts.

So I replaced the supplied bolts with some proper stainless bolts with locknuts.

Let me save you some time here.  Remove the upper radiator hose and move it out of the way.  Loosely attach the brackets to the radiator.  Slip the shroud in place so you can see which holes you will need to use.

Remove the shroud and assemble the radiator brackets to the shroud in approximately the right position.  Lower the shroud back into place.  If the shroud needs to be adjusted vertically or laterally, remove the fan and make the adjustment outside of the engine compartment.  Repeat until its right, then put it in place and tighten everything up.

This is a great mod, if for no other reason than that you get rid of all the fan noise from the stock fan.