I read this real interesting article recently entitled " Fan Brake". You wire in one or both of your thermos to come on when you put your foot on the brake. Real simple with a relay on the brake light switch. When you sit at the lights..fans on when you need them.. moving along fans only come in if engine gets too hot as normal. Works a treat on my V8 Gemi.

Heres a diagram I quickly drew up last weekend. hope it helps

sweet. cheers for that.

Interesting about the Fan Brake but i would think that it would cause excessive wear on the Thermo Fans and other related bits.

What Are the Benefits?
While this sounds an unconventional notion, it actually shows efficiency gains.
Under normal operation a car with Electric Fans sits stationary at the lights with the fans stopped and the cooling system heating up.
Somewhere before or around the time that the Traffic Lights change to green, the Thermostat turns on the Electric Fans and the Car drives away from the lights spinning the Cooling Fans.
This process reduces the pickup of the car and reduces the fuel efficiency. It may also explain the number of broken fanbelts seen near Traffic Lights due to the increase in load on the Fan-Belt while the engine is accelerating. The increase in load when the vehicle is decelerating seems to minimise this stress.
The concept of Fan-Braking is to turn the Fans on before the intersection. The electrical load introduced by this loads the Alternator and consequently slows the Vehicle down.
This process also takes some of the load off the Brakes.
It also makes the Cooling Fans more efficient because they are supercharged by the incoming airflow.
In a car with an Automatic Gearbox the driver naturally keeps a foot on the brake pedal the whole time the car is at the lights which keeps the fans spinning. Consequently the Cooling System does not suffer a lengthy period without airflow. There is only a brief reduction in airflow between the time the driver lifts the foot from the Brake Pedal and the vehicle makes sufficient forward speed to cool the engine without needing a fan.
A torquy Engine like a Red/Blue/Black Six might as well do something useful at idle and keeping itself cool shows a proven power advantage. (Davies-Craig published this on their website as part of an EWP promotion).
The instant the vehicle is driven away from the Traffic Lights the fans stop and the cool engine finds accelerating the car from the lights easier.
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Applying the Brakes at Speed:
When the brakes are applied at speed interesting things happen. If the incoming airflow spins the fans at their natural rotation speed, they show a significant reduction in their current draw.
If the incoming airflow spins the fans faster than their natural rotation speed, they take the load from the Alternator by providing a small charge to the system.
As explained earlier, if the incoming airflow spins the fans at less than their natural rotation speed, the fans are supercharged and draw heavy current slowing the vehicle down and reducing the load on the Brakes.
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What's The Downside?
The Engine is likely to run cooler around town which may effect the Engine's thermal efficiency.
Because I run Trimatics those Gearboxes respond to the increase in power and the fact that the transmission oil is cooler gives them improved coupling and longer gearbox life.
The system may not suit Manual car drivers who like to down shift before Traffic Lights. The downshift overspeeds the Mechanical Fan and to some extent achieves the same result, though this practice can impact Synchro, Clutch and Ancillary Equipment.
Clearly Fan-Braking isn't for everybody but it does reduce the stress on the Cooling System by anticipating the Cooling System's greatest stress, City Idling. It also helps the Vehicle compete against late model cars when accelerating off the mark.
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i like the idea. thinking outside the square. u'd also need a manual overide switch for the times when the bonnet is open and u dont have your foot on the brake or at least just in case.

It would work on my motorbike .U could have the thermo come on when u put the front brake on.(It's a 4 stroke, watercooled with a mini thermo)