[yogi_123rd]

The fan system has two speeds - slow and high speed. The slow speed system is used with the AC, the high speed system is used when the engine is hot. There are two relays involved located on the inside driver side fender wall near the radiator. Both these relays are the same part number and can be swapped. One relay is for the slow speed and one relay is for the high speed circuit. The ECM controls both of these relays based on if the AC is on (slow speed) and the temperature switch on (high speed) which is located in the intake manifold behind the throttle body.

When you turn the AC on, the fans should constantly run at low speed. This is would be normal (if you want your AC to work).

Now, testing with your AC turned off, if the fan is running at slow speed, find the relay that controls that circuit (disconnecting it will stop the fans) and
swap it with the other relay. If the fans stop, the relay is bad.

If the fans are running at high speed - do the same to check the relay. You also may have a bad temperature switch that could possibly be shorted telling the ECM to run the high speed circuit causing the same problem.

The problem can also be the ECM itself as it controls the relays. You can hear a click when the relay is activated. In my 90 Lesaber, my slow speed circuit runs constantly and I know the problem is in the ECM