I think I have tested and isolated the problem, but I thought I would verify before I go out and buy parts.
Several months ago, my fan speed on my heater control lost the second from lowest setting. Basically, low and second from low would operate the heater(A/C) blower at the same speed. The third and high settings worked as expected. This past weekend, the third setting now operates at the same speed as the bottom two and only the highest setting is different.
I went under the passenger side of the dash and pulled the connected from the lower motor and the blower resistor.
There is power going to the blower motor at all four fan settings. When the switch is set to high, there is no power at any of the four terminals on the blower resistor connector (not the resistor itself).
At the three lower settings, power is present at the same single terminal of the four. It is one of the central terminals. Essentially, the switch does not seem to have any effect until it is set to high.
It seems a reasonable conclusion that the switch or the associated wiring is faulty. I plan to replace the switch.
Am I on the right track or should I be looking to something else first? Reply by email and to the group if you don't mind.
Thanks,
Jason