5ktq Radiator Fan only works on high...

["Bernard Littau" <bernardl@acumenassociates.com>]

Hi list,

My '88 5ktq's radiator fan only runs at its high speed.  The fan comes on
when the engine coolant temperature reaches a certain temperature, and
cycles on and off.

I understand (I think :-) that the fan's two lower speeds are derived from
the blue resistor plate mounted in front of the radiator.

I am not clear on what commands the fan to use the lower speeds, and how
whatever that is relates to the high speed mode of the fan.

Given the above behavior, is the resistor plate definitely bad?  How is the
multifunction switch involved with the radiator fan?  Are relays suspect in
any way?

In short, how best do I figure out what is broken, so that I only replace or
fix what I need to?

Thanks,

Bernard Littau
Woodinville, WA
'88 5kcstq