North American Turbocoupe Organization

Radiator Fan switch Install
andrewjs18 Offline
Wiring In A Fan Control Relay(s)
by Martin Bokesch

I have installed a relatively clean system to control one fan on my T/C. There is no reason, as you will note further down, why it cannot control both at the same time, or with an additional relay control both separately. I wished to be able to control the upper fan with a switch, as the lower unit will come on if you activate the A/C. My application was to attempt to leave the unit as stock in appearance as possible but have additional control. I have removed the cover from the fan and A/C control unit on a number of occasions. Mounted on the right front inner fender, it is about a couple inches thick and has a large wire harness that is held in place with a single bolt in the middle of the loom to keep it attached to the controller. This controller has the Fans, A/C, EEC and fuel pump power relays in it, so best to leave the internals alone. I had to open it up as I had a poor pin connection once and opened it up to do a Repair. One thing I noticed is that Ford used Bosch relays in the controller. I’m a fan of Bosch relays, and have used them extensively in the field on heavy equipment, (Mechanic by Trade). The wiring that leaves the control relay is relatively light, so as we get into this, you will find that Ford actually spliced 2 outputs together to feed power to the fans from the controller.

The rundown. I purchased a Bosch relay, Part #0 332 019 150, 12volt 30 amp. They come in many types, but the basic version, can handle 30 amps, more than enough for both fans if required, has connections for a main power feed, noted as #30 on the relay itself. There are 2 switched power out connections noted as #87 on the relay and then there are the control power connections themselves, noted as # 85 and # 86. The reason for the choice of this model is that is has a molded in mounting bracket and is a well-sealed version of their basic model.

The relay itself is simple enough. Run the main power supply to spade connection #30. Splice into the fan connection from one of the 2 #87 connections they are both the same internally so either spade will do. Connect a control (on/off) switch to the #85 spade connection and simply connect the #86 to ground. Simple enough, took me about 4 hours!

I cannot stress the importance of good electrical connections. The Bosch relays have an option of a push in style base mount, or just an integral mount, which I chose to use. At any rate, All the connections I made, including the female spade terminal connections are soldered after light crimping. All splices were soldered and sealed with a dab of silicone than taped to stop moisture from getting to expose copper wiring.

First line I pulled, a 10 gauge red wire from the starter solenoid, positive battery connection side. I installed a 30 Amp self resetting Cole Hersee circuit breaker right at the relay, using a metal strip drilled to fit the relay stud and the “”Input side”” of the circuit breaker, The circuit breaker will be marked as to input side and power out side. This allows for a rigid mount, and the plastic cover that the coil also sits under on the driver’s side fender well will cover this. Ford put enough loom and wiring in these beasts to cover half of North America. I had no trouble routing the wire from the driver’s side all the way around to just below the control module on the passenger’s side and stayed in a loom all the way. This wire is the main feed to the Bosch Relay.

I than ran a light, 16 gauge, wire from the dash (I ran a coated double line, in case I wanted to do an additional connection of some sort in the future), from my dash switch also terminating with a bit extra at the passenger side fender well. In order for this unit to work, I located a Key switched power line under the dash and used it to feed the dash switch. As the Bosch relay uses about .2 amps to run, any feed line would work. It has been a while since I did mine so I cannot remember the exact line I tapped, but it was I believe the Sound System feed for the Equalizer, which I do not have, so it was open line.

All the wires end up below the controller on the passenger side fender well, just in front of the strut tower. This is also where the main connections to feed the fans are located. I removed all the goodies from the fender well to allow access to the little bit of space between the airbox and the tower. I mounted the Relay in this location, as it looks stock, buried enough to look like it belongs there. I traced the wiring from my fans back to the connection below the control modules, and found the Ford has 2 wires from the module for each fan feed. These wires are spliced into one feed in the harness just prior to the fan connection plugs. The fan feed positive feed wires are both brown, the primary fan has a yellow stripe and the secondary has an orange stripe in the Brown. I simply, but carefully stripped the outer cover off the brown feed wire for my primary fan, as I only did one fan, just back from the connection, carefully wound a new piece of matching 12 gauge brown wire and soldered it, piggy back onto the original. Once it was neatly sealed and retaped and put back into the harness loom, the other end of this line also ran to the relay mounting point. The relay itself has all male terminal connection on the bottom. I terminated all leads using soldered female spade terminal connectors. The fan feed plugs into # 87, the power feed into 30 and the control switch wire to # 85. When mounting the relay, run a short piece of black wire from terminal # 86 to the mounting screw for the relay, as the relay requires a ground line. Gauge is not important, as this is just a .2 amp circuit, so 16 gauge would be lots. If you wish to control both fans with one switch at the same time, just repeat the splice with the second fan wire and connect to the open #87 terminal on the Relay, as there are 2 power outlets on the rely. If you wish to control them separately, you need to run 2 switches, 2 relays, but the wiring would remain identical in both cases.

Why I did the job this way! I wished to have additional control over the fans, as we all do. I also wanted to keep things looking stock. The additional point was that it should be able to remain operational as built, as I am not the only driver in my family, and if someone does not turn on the fans, no problem, the stock system is still in place and still functional. The additional switched circuit that I installed is piggyback to the original, causes no feed back to the control module, as it is all connected downstream of the original relays. The reason I used Key switched power under the dash for my small control line is that when I or others turn the car off, if the manual fan switch is left on, the relay will turn off with the key and the fans will not stay running. Simply put, the dash switch wiring supplies 12volt at about .3 amps to the relay switch that is internal to the Bosch relay. When the switch on the dash is turned on, it in turn excites the relay and connects the #30 main power feed to both the #87 controlled power out feeds. Which will kick in the fan(s).

As you can see, there's not a lot of wiring schematic to get into, as you are running all new lines, and other than tapping into the existing fan feed lines, not really using any of the original wiring. I did stay in the looms with all the wiring, and it kept the appearance neat and tidy, so other than a spare switch I mounted under the dash, just above the throttle pedal, one would never know that the systems exists.

Again I stress enough the need for good electrical connections, and using a circuit breaker or 30 amp fuse in the main feed to the Bosch Relay, to protect the feed circuit.

It main not be as simple as a lot of the other post, which say just use big wires and big switches. After being in the trade for 25 years, I have learnt the correct ways and what works and survives. Although the fed line is longer than I like, there is no strong feed available on the passengers side unless you wish to tap into the control module feed, and I thought best leave this alone, as it could get expensive if a short occurs.


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