Dave:
Thank you. Any ideas on how to test the fan to see if it has two speeds? Does it kick to a higher speed at some higher temperature? If so, if my is not working, I presume it would likely shut off when it hits that temp, right?
MOG37, yes the higher fan speed is to offset a higher coolant temp. If you are comfortable with electrics then breaking connection to fan itself and connecting it directly to battery should prove it works and can run at a higher speed than you are currently getting.
If this proves to be the case then maybe the high speed fan relay is faulty. Check with replacement. This relay is the first of a row of five similar size ones with low speed relay adjacent.
Each of the relays are triggered by a ground connection to relay coil (pin 85) provided by ECU and dependant on coolant temp. I suspect after the low speed one is triggered it remains on and with further coolant temp increase the high speed relay is triggered effectively by-passing the dropper resistor that limits fan to lower speed.
BTW this resistance described as "Ford cooling fan resistor plug" of rectangular shape should be found in loom close to fan connection socket, and a clear sign you have a two speed cooling fan system.
