TWIMC:
I have been mulling over this very idea of adding some radiator  fan
speed indicators. 
Allow me to share the (unexpected) results of my prototype(here forth to
be known as the Lewis mod).After studying the schematics I formed a plan
that satisfied my four basic project guidelines:
1>minimal parts
2>cleverness of design
3>ease of assembly
4>effectiveness

Step one;I only used a momentary contact pushbutton with built in LED ,
four wires and push on terminals to connect the previous two items.

Step two;With the above parts I was hoping to activate high speed on the
radiator fan and monitor the automatic hi/lo speed of fan motor with
bright/dim of LED by judiciously selecting its series resistance.To
accomplish this I focused my work on the second stage radiator fan
relay. I removed the relay cover and drilled a hole in it for wire
egress. Then I soldered the four wires to the  terminals inside the
relay;  85,86,87 & 30 on my vehicle. I mounted the LED/switch in the
blank under the emergency flasher rocker switch.Two of the wires were
connected so upon switch closure the relay was energized, hence
activating rad fan to hi.The positive lead of the LED I connected to the
output of the relay i.e. the hi input of the fan.I found this wire could
monitor both hi and low fan speeds;6 volts=low, 12volts=high. The final
wire was ground and went to the resistor which was connected to the
negative lead of the LED.

Step three:it was easy for me to assemble and minimal impact on existing
hardware.

Step four; testing.To initiate  hi/lo fan speed I jumpered the proper
wires at the thermostatic switch plug. The LED displayed a corresponding
bright/dim!! The switch also operated the hi speed function!! Everything
worked as planned the first time,how many times does that happen!?!Now
for the unexpected results.During the first test drive, upon reaching
around 40mph, I noticed the LED was on!How could this be?The engine was
cold and the temp needle had not even moved!While pondering this I
stopped for a red light and it went off?!?I once again got up to speed
and it came on again.Have you figured it out?The fan was free wheeling
from the force of the air being pushed through it, turning the motor and
causing it to behave as a generator!!
As I see it this makes  the LED a dual purpose indicator:
A> hi/lo rad fan indicator(now only effective at slow speeds).
B> Rad fan bearing condition indicator! If the bearings start drying out
and stiffening up the freewheeling effect would be reduced.

Anyway, I'll keep evaluating it and try to keep you updated.

Ken Lewis  kdlewis@juno.com

86Doublecab pickup
85GL
60 356(almost finished)
61 AH Sprite (for sale)