To walk through it together, all you need the information on the relay
locations, and David’s wiring diagram which is the same as Fig.24 for
the Compressor Clutch and Auxiliary Fan from the Electrical Guide for
your 96 4.0L.
What David did is add a relay which provides a Parallel ground, or
alternate ground, for the Cooling Fan Relay when the compressor clutch
is engaged.
The original wiring circuit has the Radiator Thermal Switch as the ONLY
control for the Cooling Fan. In the original circuit, when the
Radiator Thermal Switch is closed (coolant temperature elevated) a
ground is provided to the relay, and battery (NOT ignition-switched)
power operates the relay and provides power through the closed relay to
the Cooling Fan.
David’s added relay is operated by ignition-switched power from the
Red/Brown wire from pin 87 of the Compressor Clutch relay whenever the
key is in the run position and the compressor clutch is engaged. This
added relay switches a ground or supplies a ground in parallel with, or
around, the Radiator Thermal Switch.
When the key is turned off and the compressor clutch is switched off,
the Cooling Fan may still run if triggered by the Radiator Thermal
Switch, until the coolant temp in the radiator at that switch falls
below the set point, and the ground is no longer supplied to pin 85 of
the Cooling Fan Relay.
Apparently David mounted the new/additional relay next to the
Compressor Clutch Relay which is the forwardmost on the Right Front
component panel under the bonnet. You will see the pin numbers and
wire colors in the Electrical Guide Fig.24, and also on David’s pdf of
that page with his added relay & wiring.
You then need to run a wire from the new relay, across the radiator top
rail, to the Cooling Fan Relay, pin 85, Green/Brown wire. That Fan
Relay is the forwardmost on the Left Front Component Panel.
I would suggest that any time you make any modification in the original
wiring, that you do the following:
(1) Carefully walk through the proposed new or additional circuit to
make sure you understand exactly how it will work and change function;
(2) Record/save a document with complete notes and/or diagram of the
circuit, so that several years after making the change, you will know
exactly what was done & why, and how function was changed.
Not everybody is as skillful (skilful in UK 
and/or careful as
David, to walk through the process and to make sure the circuit is the
same on your 96 4.0L as on his 94 6.0L. He devised a very simple and
effective solution.
George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Veekay valde@verizon.net
Thank you. It does help, and I plan to hunt down those
wires this weekend. Undoubtedly I am closer with your
help than without.
I was hoping someone could dumb it down for me and point
out specifically where, under the hood these wires can be
found.
// please trim quoted text to context only