This one's stumped me.

93 Cav - cooling fan will not come on in response to coolant temp gauge alone. I let the gauge go almost to the Red (250) before manually kicking on fan (via turning on AC) - don't want to cook the head.

Cooling fan will come on when A/C is turned on (no help now since I'm low on 134A due to leak...) - assume this clears the relay as the problem

Coolant fan comes on if I unplug coolant temp sensor (assume ECM is OK due to this observation - is it the ECM which commands on fan when coolant sensor goes open?)

Have swapped relays with identical relays on car - no change.

Any thoughts???

New sensor or try a new relay pigtail. The connectors are aluminum and get really tarnished inside. Good Luck.

New sensor or try a new relay pigtail. The connectors are aluminum and get really tarnished inside. Good Luck.

Already tried sensor - no help. Sensor is common to ECM and gauge - gauge appears to be working properly (don't know how to confirm). Appears to be same relay used to turn on fan from either ECM command on or from AC clutch engage request. That's why I'm stumped - everything else that can turn the fan on does - just not the coolant temp.

?????????????????? I'm stumped. or is it stumPPed????