Wayne Cook
June 1, 2000

Step By Step

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In this comparison of a prototype version of the new Flex-a-lite electric fan (right) to the standard Flex-a-lite Black Magic 150 (left), you can see how the fan blades are flush with the shroud on the new fan. Notice also that there is no protruding mainshaft for the fan drive motor. These factors combine to provide a 3/4-inch clearance at the water-pump mainshaft when installed in a 289-powered ’65-’66 Mustang.
The brackets furnished with the ’65-’66 Mustang unit allow attachment directly to the radiator-core support. The fasteners used to install the fan brackets to the core support will vary in length depending on the thickness of the radiator. Installation obstacles will vary from car to car. For example, some core supports may have openings for air-conditioning lines, as ours did. At the time of our installation, Flex-a-lite had not finalized the bracketry, but we were able to mount our unit without difficulty. Also shown is the electrical packet containing everything you’ll need to wire the fan correctly.
The car used for this article is a ’65 Mustang 2+2 fastback with air conditioning. Here’s the landscape underhood, including the original engine-driven fan, before installation began.
First, the factory fan and spacer must be removed. To hold the water-pump pulley in position, replace the long bolts with short ones.
Because our subject is an air-conditioned car, there’s a small, factory shroud that must be removed also.
In this view, it’s easy to see the rubber seal around the edge of the shroud assembly on the Flex-a-lite prototype. Also shown is the thermostatic bulb, which must come in contact with the radiator surface. On the other side, there’s a control knob which allows adjustment of the on/off temperature for the fan motor.
Before we installed the fan on the car, we test-fitted the supplied early Mustang brackets. The large bracket at the right has an opening to allow access to the temperature-adjustment knob.
We slipped in our unit without the brackets to simplify the placement of the fan. The unit is a perfect fit over the radiator with the control box on the driver’s side. We slid the fan into the car, then rotated it 90 degrees to the right (as you face the car).
With the fan in place, we installed the brackets onto the fan housing, then made the holes in the core support to accept the attachment bolts. The length of the bolts will vary with the thickness of the radiator.
Flex-a-lite’s supplied electrical kit is complete, right down to the wire ties. That’s a circuit breaker at the top in the middle.
This special three-way connector is used to wire-in air-conditioned cars so the fan will come on when the A/C is switched on.
One look at this diagram tells you that wiring the Flex-a-lite electric fan is not difficult.
This view from the top shows the ample clearance between the water-pump mainshaft and the fan assembly. This is the all-important dimension for obtaining a trouble-free electric-fan installation.

Vintage Mustangs are not well-endowed with radiator frontal area, which makes them especially vulnerable to overheating in warm weather or when stuck in stop-and-go traffic. Add factors like air conditioning along with healthy engine modifications, and overheating becomes a real and distinct possibility. But with a Flex-a-lite electric fan, you can avoid becoming sidelined with overheating problems.

Last year, when we installed a Flex-a-lite Black Magic 150 on our ’66 Mustang, we encountered some very close clearances, even to the point where we had to mount the unit slightly off-center to provide space between the fan motor and water-pump mainshaft. Now Flex-a-lite has added a new electric fan, PN 475, that is designed to eliminate the clearance problems on ’65-’66 Mustangs, making the installation much easier.

The advantage to an electric fan is that it runs at full rpm even when the engine is at idle. The fully shrouded and sealed Flex-a-lite unit ensures that all air moved by the fan travels through the radiator. Most early Mustangs had no fan shroud at all, and even the ones equipped with air conditioning came with just a small shroud of marginal efficiency. Another added advantage to an electric fan is the engine no longer drives the fan, so there’s more horsepower transferred to the rear wheels.

While the mounting bracketry for this new Mustang fan is still in the development stage, you should be able to order the fan by the time you read this and be confident that it’s going to fit your ’65-’66 Mustang.