You need to apply air pressure to the fan clutch to get it to engage. Modern over-the-road trucks use this same system, but opposite, as they apply air to stop the fan (more fail-safe). You need to add a 24VDC air solenoid valve to do so, and "T" it in after the mechanical valve on the upper radiator hose, as the fan actuator solenoid is purely mechanical. Then, activate that solenoid via one of 3 methods:
1. Manual switch on dash. Likely to be forgotten to be turned on or off.
2. Automated via tied into the AC compressor clutch power feed (compressor on=fan on). Not most efficient, but better than #1.
3. Automated via a pressure switch on the AC high side pressure line. Then, fan only runs when it really needs to. Research set-points of switch to buy. Better than #2.
You could go really simplistic and use an air valve to feed the clutch air pressure, but I'd say that is a hillbilly version of #1. Could also bolt the fan clutch together (emergency mode), but running it all the time is a huge power and mileage drain on the engine, as that fan pulls a lot of air.
This is all assuming an A2, not sure which you are speaking of (A0?) Not sure how A0's and A1's run their fans. I have an A2.
