I just want to add to this thread that if you are having issues with the stage one fan not coming on, or the second stage for that matter, and you are also experiencing intermittent a/c issues, to consider the compressor clutch coil.

Here is an excellent write-up

I have the replacement resistor and plan do the install, but I think now I'll wait till I have a moment to check the ohm reading on the compressor coil. If it's bad, I'll replace it at the same time.

Lately I've been having strange overheating issues. I'll be in stop-n-go traffic or in a drive-thru and look down to see the car is on it's way to overheating. If I turn the a/c on, it usually cools down, but not always. So I'm under the assumption that I have a bad cooling fan resistor or a/c clutch coil or both. I replaced the cooling fan assembly just a few months ago, and that seemed to help for awhile but I believe the fan resistor has a habit of failing fairly often.