The original cooling fans fitted to most classic-MG cars were engine-driven mechanical units, bolted to the water-pump pulley and turning constantly whenever the engine ran. Engine-driven fans have two disadvantages compared with modern electric fans, they consume engine power continuously, sapping a small but measurable amount of crankshaft output, and they run at a speed proportional to engine speed rather than to cooling demand, so they move little air at idle in traffic where cooling is needed most and continue to absorb power at motorway cruise where ram air through the radiator is already sufficient. Revotec electric fan conversions replace the mechanical fan with a thermostatically-controlled electric unit that runs only when the cooling system actually needs the additional airflow.
Revotec Fan Kits
Revotec is the established UK brand for electric cooling-fan conversions on classic British cars, manufactured in the UK and engineered to fit the original radiator mounting using model-specific laser-cut aluminium brackets, with no permanent modifications to the radiator, engine bay, or bodywork. The kits use a sealed, balanced, waterproof fan motor mounted in front of or behind the radiator, an adjustable electronic controller that allows the switching temperature to be set to suit the car's operating conditions, and a convoluted top hose replacement incorporating the temperature-sensor boss, along with the brackets, relay, wiring, and fittings for a complete installation. The controller switches the fan on when the coolant reaches the configured threshold and off again when it drops below a slightly lower threshold, so the fan runs only when needed, typically during slow traffic or after the engine has been shut off following a hard run, with the engine pulley contributing zero parasitic drag during normal cruising. Because all the early cars left the factory positive-earth, the controller, motor, and override switching are polarity-sensitive, so the kit ordered must match the car as it is currently wired rather than its original specification, with positive-earth and negative-earth versions available.
Performance & Practical Benefits
The performance benefits of an electric fan conversion are measurable but modest, typically a few horsepower returned to the crankshaft at higher engine speeds where the mechanical fan was consuming the most power, but the practical benefits are more valuable, cleaner under-bonnet space with no spinning fan blades to navigate around during service, quieter cabin ambience at speed as the mechanical fan was a significant noise source, faster warm-up from cold as the fan stays off until the coolant reaches temperature, and substantially better low-speed cooling capacity, as the electric fan can run at full speed regardless of engine speed where the mechanical fan was producing minimal airflow at idle. For cars used in modern slow-moving traffic the low-speed cooling benefit alone justifies the conversion, and the improvement is most dramatic when the fan is combined with an aluminium radiator, the two together addressing the cooling system's main limitations simultaneously.
Override Switches, Accessories & Installation
The Revotec accessory range extends beyond the primary kit, with a classic override switch that allows the fan to be brought in manually regardless of temperature, useful in queueing traffic, on long ascents, or when parking a warm engine, and a hot-start arrangement that keeps the fan running briefly after shutdown to prevent the heat soak that can boil coolant in the head when circulation stops. Installation is workshop-level work, the original mechanical fan blades and spacer being removed from the water-pump pulley while the belt remains in place to continue driving the water pump and alternator, the electric fan mounted to the radiator on its brackets, the controller fitted in the engine bay, and the wiring routed through a relay to handle the fan's current draw with a fuse for circuit protection, the temperature sensed from the top-hose boss. Owners running an uprated aluminium radiator should confirm clearance between the fan body and the replacement core before committing, as some alternative-radiator depths reduce the available clearance compared with the original item.