This is not the most elegant method but it's virtues are simplicity, no soldering, easily removable and no altering of the existing system. Frankly, I tried it as a temporary test and never got around to seeing a pressing need to change it. Please forgive me for being too detailed here but, for some, it will be a first Morgan modification.

The principles are easy to understand...the wire delivering power to the rad fan goes through a heat sensitive switch. This switch turns the fan on and off by allowing the current through (or not) at preset
temperatures. The advantage with a bypass switch is that it allows you to turn on the fan BEFORE the engine gets hot and yet leaves the original installation in place in case you forget.

To do this you must create a second pathway for the power around the rad switch and then on to the rad fan. This new path run through a switch YOU control and near at hand when you are driving.

First disconnect the battery.

Now you need a few bits to add to what is already there. Two splitter (?) fittings (one female into two male), two female connectors, one simple on-off switch, 2 wood screws and 10 feet of two strand wiring. The rad switch is found on my car at the bottom of the radiator. They have two prongs or male connectors for the power going in (with a plastic covered female connector) and the same for the power going out. I simply removed the connectors, slipped on a splitter on each of the switch's prongs and reconnected the rad fan's wires to one (each) of the sets of splitter prongs. So now I am back as I was originally with a normally functioning fan with the exception that I have an extra connection available in and out at the rad switch.

I then used the electrical wire in the appropriate thickness (tell the fellow at the auto store where you buy this stuff that you hooking up a rad fan...) I ran it from the rad fan switch up to and then along with the other wires on the outside of the inner wing, then pushed through the rubber grommet through on the firewall near the driver and into the car.

Here you have options on what and where you wish to have your switch. Though you could use one of the unused switches on your instrument panel, I would suggest you leave them alone unless you are electrically inclined..I also have doubts that an unused rear fog lamp switch can happily take the power of a big rad fan (unless you have one of the cars fitted with a rad fan relay and you wire to the relay or you install a relay). I bought a small chrome push-pull switch, made a small L-shaped bracket with three holes on one side (to wood screw it into the wooden member under the dash and to the side of the car) and then mode a hole in the other side of the my L-bracket to put through the pull switch and tighten it. In this place it is easy to reach, easy to wire and still out of the way and hidden. Wire each of the ends to one of the wire terminals on the switch .

Now go back to the radiator, attach two female connectors to the wires (easy to do) and plug them in to the extra male connectors you put in. Reconnect the battery. (If you left the new switch on the fan should come on as you are connecting the battery...turn it off).

Test the switch. Now turn the switch off and let the car heat until the rad fan comes on by itself. If it does you are fine. Turn everything off and affix the wires where convenient with electrical tape so it is out of the way but not stretched.

When you turn it on, you must look casually at your passenger and explain that you are "activating the Turbocharger".
 

PORTING YOUR HEADS

This process matches the exhaust ports of your engine heads to your exhaust manifolds.