Hi. Thanks for using JA! I will try and help you out.
Here is the information on the cooling fan operation of your engine. This list give details of the fan on and off conditions.
Please let me know if you have any more questions.
Cooling Fan On Conditions (On/Off Fan)The ECM will turn on the cooling fan, if any of the following conditions are met:Engine speed is less than 2250 rpm.The engine is not running.The engine is cranking.The temperature of the coolant temperature sensor for the C-10 and the C-12 engines is greater than 96 °C (205 °F). The temperature of the coolant temperature sensor for the 3406E, C-15, C-16 and C-18 engines is greater than 102 °C (216 °F).Active diagnostic code for the coolant temperature sensorThe intake manifold air temperature is greater than 87 °C (189 °F).The intake manifold air temperature is greater than 72 °C (162 °F) while the boost pressure is greater than 70 kPa (10 psi).The "Fan with Engine Retarder in High Mode" is programmed to "YES" and the retarder has been on at least two seconds.The "A/C Switch Fan On-Time" is programmed to a value above 0 and the A/C high pressure switch is Open. The ECM is counting after the A/C high pressure switch has closed.The "PTO Activates Cooling Fan" parameter is programmed to "Continuous" and the PTO On/Off switch is on.The manual fan override switch is on.
Cooling Fan OFF ConditionsThe cooling fan will be turned off by the ECM if engine rpm exceeds 2300 rpm or when all the following circumstances are met:The engine coolant temperature for the C-10 or the C-12 engines is less than 92 °C (198 °F).The engine coolant temperature for the 3406E, C-15, C-16 and C-18 engines is less than 98 °C (208 °F).The fan has been on for at least 30 seconds.The intake manifold air temperature is less than 53 °C (127 °F).The "Fan with Engine Retarder in High Mode" strategy is not active.The "A/C High Pressure Switch Strategy" is not active.The "PTO Activates Cooling Fan" strategy is not active.The manual fan override switch is off.
I thought that the fan kicked-in a lot sooner , and maintianed around 180 F but I may be wong. I began paying more attention after the truck received bad twist when it went in a ditch and opened up a seam in the rad. Until I can get that repaired I keep the rad cap loose and it dosen't leak when not under pressure. I would perfer the temp. to be lower.
Thanks for the information. On earlier engines the fan did come on sooner. But when 2WS engines came out, the temp went up to 217. This is also when Cat put 2 thermostats in instead of one. This helped up the flow of coolant.