cwmarch@aol.com

Don't know everything the coolant sensor feeds. The sensor I replaced is in the upper radiator pipe/hose and has 2 leads that go to the fan controller(via the 6 pin). The 6 pin has short, approx 5" leads to the controller. My controller is mounted on the lower back of the fan box. Follow the hydraulic lines from the fan motor - should lead to the controller. The engine was running hot, not just an indication problem. Evidentally the coolant sensor wasn't sending the correct signal to increase fan speed(intermittently).

Had intermittent overheating on my 400 ISL, 03 CC Intrigue, side radiator. After talking to a Cummins mechanic (not the service desk) in Albuquerque, I disconnected a 6 pin connector on the engine cooling fan controller. Disconnecting this plug causes the engine fan to run at highest speed, if the fan/controller is working properly (eliminates that as the problem). Took a while for the engine to heat up but I found the loaded temp ran around 185 degrees, the set point for the thermostat. Proved the termostat OK. Ran the Rockies and then central TX in 100 plus temps and never saw over 200 degrees on the Silverleaf (proves the cooling system has sufficient capacity). The 6 pin plug is coolant temp, air charge temp, power, ground. Replaced the coolant temp sensor and my problem went away. Bottom line, disconnecting one plug COULD eliminate a lot of potential problems - easier to find the culprit.