'95 Z28.

First I checked the relays. They work fine.

Then I unpluged the computer and grounded the harness at the correct pins as shown from shoebox's web site. They then work.

Turned the car on with the AC running. Still don’t work

Checked the ohms range on the temp sensor. It was within range as my repair manual said.

What else am I missing?

 

If I understand, you grounded the lines at the PCM that go to the relays and the fans kicked on. That leaves 3 other possibilities since I doubt you have an intermittent break in the wire. Two are unlikely, that is the connector is bad at the PCM. You could tell that by looking. Or the PCM has a bad ground. Also unlikely but check them just to be sure. Two of the 4 wires are tan/white on the red connector and on the blue connector. These 2 wires go to the ground near the ignition coil. The other 2 are black/white and are on the red and the white connector. These 2 go through a splice and end up at the ground point above the starter. Ohm them end to end.

The last possibility is the output or I should say the driver circuits in the PCM are bad.