"Fpbear II" wrote in
. net:

I have a 12V 0.8A Nidec TA450DC fan in some equipment and I need to
slow the fan down to about 75% of its speed. It has four leads: red,
black, yellow, and green. I guess that yellow is the RPM sensor and
green is the high/low voltage sensor.

I tried using a 5-ohm resistor as well as a zener diode on the red
lead. This did not work because the equipment senses something is
wrong, and the fan won't spin. To try another strategy, is there
something I can place on the green or yellow lead to trick the system
into reducing the fan speed?

The usual way to slow down a DC fan is to drop the voltage below 12v
until you get the speed you want. But it sounds like you've tried that
and it didn't work. What kind of equipment is it hooked up to?