There have already been a few AU fan installations detailed on this forum. The installation of the fans has usually been performed very well, but the electrical side has left a lot to be desired.
Knowing that none of the previous installations were to my standard, we knew that we would have to do some research.
The first thing was to find out how Ford wired up the AU fan on the AU falcons. Below is the circuit diagram.
The PCM allows three options. The first is for no signal and no fans. The second involves a signal from EDF1, which runs the fans in series at low speed. The third involves a signal from EDF2, which runs the fans in parallel at high speed.
The next thing that we needed was some switches to do the job of EDF1 & EDF2. Before I could decide on the appropriate temperature for the switches we had to decide where we were going to locate the switches.
We chose to locate the switches at the exit point of the radiator. The reasons for this location were twofold. The first was that we didn’t want the switches to ever become exposed due to a loss of water from the radiator. The second was that we wanted to control the temperature of the water leaving the radiator. Switching at the thermostat or radiator inlet gives you little control of the temperature of the water leaving the radiator.
Next to decide was the style of switch. We quickly decided on the type that screws into the radiator. These are used by many car manufacturers such as Ford, Mitsubishi, Nissan etc. This decision was made easier by my past experiences with capillary switches and the $2 thermal switches.
Deciding upon suitable switching points was the next step. I run a 180 degree Fahrenheit thermostat, so the points had to be compatible with that. To choose the switching temperatures I chose to copy the automotive industry. Most cars running 193 degree Fahrenheit thermostats, so I was looking for a switching points around 13 deg. F lower.
Searching through electrical automotive catalogues, we managed to find a dual switch that fitted the bill.
It’s properties were:
Part number: 2FS 214
Low temperature switching points: On 80 off 75 deg. C
High temperature switching points: On 87 off 82 deg. C
Thread: M22 x 1.5
RRP: $140 (far less for trade)
Below is the switch installed in the radiator:
The next step involved deciding upon the wiring. Obviously the wiring was to be based upon the factory setup, but using temperature switches instead of a computer. There was also some other features that we wished to include. Some people have reported that they have had trouble starting their cars when the fans were running. Therefore we wanted the fans to stop when the engine is cranking. This can easily be achieved by running a wire from the “start” terminal of the ignition to a normally open relay. We also wanted the fans to not run when the key is in the “off” position. This will eliminate the risk of the fan unexpectantly starting when working on the car. If the car is hot when you shut the motor down, you can easily leave the ignition in the “accessories” position allowing the fan to run.
Below is the wiring diagram that we came up with:
For the relays, we chose to use a solenoid block like those that Ford used. Below is a picture of the installed relays:
We hope you have found this information useful.
XBGS351 & SILICON