One of the most common Scimitar modifications is the adddition of an over-ride switch to allow the fan to be switched on as the driver's temperature rises.
The following diagram shows how to add a simple switch that bypasses the otter switch. It can therefore switch the fan on either when the driver doesn;t trust the otter switch, or when the otter switch is faulty and is obviously not going to bring the fan on before the pressure cap lifts off.
The addition of two wires from the otter switch terminals back to a dash-mounted on/off switch allows the fan to be switched on when required.
The main drawback to this system is the "trombone" of extra wiring, but it is very simple to fit, and requires no disturbance to the existing wiring other than piggy-backing the wires onto the existing otter switch connections.
An improvement would be to run only one wire down from the dashboard, connecting it to the motor-side of the otter switch, and obtaining the incoming switched +ve feed from a convenient terminal on the ignition switch. This is a lot harder than it seems, and because of the variations in wiring between the different Scimitars is not going to be explained in further detail here.
A far better system is to use a relay to supply current from the battery directly to the fan motor, with the otter switch controling the current to the relay activation coil. This system does however require modifying the wiring.
Supplying the fan motor via a relay from the battery can give better current flow, and reduces the load on the otter switch contacts
This system has some clear advantages
It is important to fuse the supply to the relay as close to the battery as possible. Fitting a relay with a built-in fuse to the bulkhead close to the battery is the most practical way to achieve this.
There is nothing to be gained by arranging for the fan to continue to run eeven when the ignition is off. Because of the low configuration of the GTE radiator no thermo-syphon effect can be achieved. You will however run the ruisk of flattening the battery if the fan should decide to run overnight. (Coupes and Sabres can benefit from running the fan with the iginition off because there is a thermo-syphon effect to be exploited ).
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