Fan not working - A/C seems to work though - how do I troubleshoot?

[deosingh]

I have an 1989 240 N/A.

When I slide the fan switch to the 1, 2, 3, or 4 position, it doesn't seem to work whether the A/C button is on or off. I think the A/C still works because when I hit the A/C button, I can hear the A/C fan turn on and the button light turns illuminates.

Also, while I'm driving, if I hit a bump and the fan slider switch is in the 1, 2, 3 or 4 position, it turns on blowing air for a short time, then turns off until I hit another bump. Similarly, if I hit a bump and the fan slider switch is in the 1-4 position and the A/C button is on, cold air is blown out of the vents.

This indicates to me a loose connection somewhere, but I don't know where to start looking? Anyone have any advice or an electrical schematic that would be helpful?

Thanks.