Tonywham Posted July 11, 2023 Share Posted July 11, 2023 2016 MP7 CXU 613 Even when it’s actually 65 degrees out while parked and at idle my outside air temp will suddenly rise to 135 degrees and my water temp will climb to 195 degrees and my A/C will not cool as well. I can rev up to 1200 rpm for several minutes and it will drop back to close to the outside air temp and A/C will be cold. When pulling a load on a hot 100 degree day my max water temp that I have ever seen is 208 and oil temp 245. What have I got going on? Quote Link to comment https://www.bigmacktrucks.com/topic/73041-outside-air-temp-rising-at-idle/ Share on other sites More sharing options...
Mackpro Posted July 11, 2023 Share Posted July 11, 2023 The ambient air temp sensor is mounted in the upper right areas of the aftercooler and the AC condenser right below it. When you sitting still and fan clutch not engaged, the heat off the condenser, aftercooler and radiator cause the ambient air temp sensor to read higher than the actual outside air. Once the fan kicks in or you idle the engine up , the fan pulls the actual “cooler” air past the sensor and the readings go down. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73041-outside-air-temp-rising-at-idle/#findComment-534647 Share on other sites More sharing options...
Tonywham Posted July 12, 2023 Author Share Posted July 12, 2023 Thanks for the reply. I was thinking I might be having problems with the fan clutch not engaging at a lower temp. Is the clutch controlled by a sensor or computer? Or possibly a faulty thermostat? Quote Link to comment https://www.bigmacktrucks.com/topic/73041-outside-air-temp-rising-at-idle/#findComment-534681 Share on other sites More sharing options...
tjc transport Posted July 12, 2023 Share Posted July 12, 2023 even with a properly working fan the ambient sensor can read wrong as it is not in the airflow. .so when sitting it reads the heat off the engine and radiator. 1 Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment https://www.bigmacktrucks.com/topic/73041-outside-air-temp-rising-at-idle/#findComment-534690 Share on other sites More sharing options...
Mackpro Posted July 12, 2023 Share Posted July 12, 2023 2 hours ago, Tonywham said: Thanks for the reply. I was thinking I might be having problems with the fan clutch not engaging at a lower temp. Is the clutch controlled by a sensor or computer? Or possibly a faulty thermostat? Engine ecm looks at coolant temp and AC high pressure switch and possibly other sensors to determine if the fan needs to be engaged. Start the engine up cold . A/C off . Rev it to about 1200 and listen for the fan to slow down. Then unplug the Green pressure switch on the AC line by the radiator. The fan clutch should speed up gradually. You should be able to feel the air flow through condenser. We have to pull the after coolers off ours every 2 years to wash the radiators out. A fault code on the oil thermostat solinoid or the piston cooling oil solinoid can cause fan issues as they are on the same power circuit on most truck pre-common rail 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73041-outside-air-temp-rising-at-idle/#findComment-534692 Share on other sites More sharing options...
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