Any ideas what I should check.  The radiator fan comes on low speed when I
turn the ignition switch.  It runs continuously regardless of temperature
(even if sitting overnight).  It goes off when I shut the engine off.    I
replaced the fan switch with a new one and no change.  I jumped the wires
that go to the switch and it is operating correctly, both high speed and
low.  I haven't tried replacing the relay behind the headlight b/c I thought
if that goes bad, the low speed fan would never come on.   Anyone have
experience with this problem.

Thanks
Dave