I'm having a problem with my heater ventilation fan.  I've got a 1997 Volvo
850 with manual temperature controls.  My fan speed only works on speeds 2,
3, or 4.  Speed 1 does nothing.  I've checked the fuses, but I know that
speeds 1-3 are on one circuit and 4 is on it's own, so that shouldn't be the
problem.  Also, I've swapped out the switch for another used one, and it
made no difference.

Any ideas on where I should look next?  Thanks in advance.

Tom.