Taking in this week’s discussion, I decided it would be a good idea to set
up the fans to keep running until the engine was cool, even if the key was
in the off position. It’s a very simple mod, you barely even need to open
the bonnet. Here’s how it works, at least on a Series II, it will probably
be much of a muchness on any year:
-
Jumper around the otter switch. The otter switch will variously be
located on the front of the radiator, in the header tank, or on the lower
hose. Just use a double spade connector or a piece of wire to connect the
two leads. (You’re really jumpering to ground, so there’s no need to worry
about shorts, don’t get fussy with insulation) -
Swing down the dash center panel.
-
Obtain a 30 amp inline fuse, I prefer the rectangular fuses to the
traditional buss fuse. Either style is available from your local auto parts
store. Crimp (solder if you prefer) a female spade connector to one side, a
male spade connector to the other. -
Here’s the tricky part: there are several undifferentiated green wires
attached to fuse 6. One is for the fans, the others are for other stuff.
We’re going to be working with everything powered, so be careful to avoid
shorts: If you turn the ignition key to the on position, the fans will
start (since you’ve jumpered out the otter switch). Remove the green wires
one by one until the fans stop. The wire that makes the fans stop is the
one you are are interested in. Plug all the others back where they came
from, keep the fan wire disconnected. Turn the key to the off position. -
Plug the fan wire into the male spade connector of your new in-line
fuse. Tape this connection well to prevent shorts (or use heat shrink if
you’ve got it). -
You now have to find an unfused, always-powered connection. Fuses 1-4
will always have power. The wires along the left side of these fuses should
be attached to an always powered bus. Connect the female side of your
inline fuse to this bus (there will be extra lugs). If you’ve chosen well,
the fans will come on immediately. If not, just try another lug. To make
sure you’re on the unfused side of your chosen fuse, remove the fuse, and
the fans should keep running. -
Remove the jumper from the otter switch, and button everything up.
The fans will stay on as long as the otter switch calls for cooling, even
if the engine is off. Once the engine is cool, the fans will stop. (If you
have a very hot engine, you may get an on-off-on-off effect for a while,
due to thermosiphon, but it will stop in a few minutes.) The mod will work
on A/C or non-A/C cars.
If you’re worried about the otter switch failing, and causing your battery
to drain, my experience is that it becomes non-conductive when it fails,
there should be no problem.
I still have no clue why you would want a manual switch to turn the fans on
and off. If the otter switch fails, it’s a piece of cake to jumper it out
so that the fans will be on all the time. Then just replace the switch when
you have the chance.
Mike Frank
1969 E-Type 2+2
New York