DoctorQ

Looking for feedback from members using OBDII Scan Gauges (i.e., Aeroforce, PLX, etc) to monitor water temperature. Why just scan gauges? Trying to compare apples-2-apples (or as close as possible) to how I monitor my water temp (which I use the PLX OLED OBDII scan gauge). The 2005+ Mustang GT does NOT have a H20 temp sensor. Rather, the GTs are configured with a CHT (Cylinder Head Temp) sensor. The 2005+ 4.0L V6 has an ECT (Engine Coolant Temp) sensor which is mounted in an actual coolant passage. The issue with ECT sensor equipped vehicles is that an accurate reading of CHT cannot be obtained (important for fuel economy and emissions). The 2005+ 4.6L GT is equipped with a CHT sensor, no ECT. The CHT is mounted into the wall of the cylinder head and is NOT connected to any coolant passages… the PCM uses algorithms to ‘interpret’ water temp readings.

Anyway, here’s the issue… My cooling fan does not kick on until water temp (per my OBDII scan gauge) reaches 215F… it will run until temp drops to 202F, then shuts off. Others have indicated that the low-speed fan should kick on around 200F, and drive temp down to 192F. I took it into my local Ford dealership service, and they advised my cooling fan is “operating within spec and cycling within parameters” (stating fan engagement is based on various PIDs, not just water temp). If anyone is willing to run a quick observation on their vehicles, I’d like to know at what temp your cooling fan engages. I simply had the car idling in the driveway and waiting for cooling fan to kick on.. then observed gauge water temp. Then as temp dropped, noted at what temp cooling fan turns off. (again, mine turned on at 215F… and turned off @ 202F. Thus my temps consistent run 200+ , and up to 230F when under load)… this seems too hot. I appreciate any/all input.

(1) At idle, my cooling fan turns on under 200F
(2) At idle, my cooling fan turns on between 200F – 214F
(3) At idle, my cooling fan turns on at 215F +

DoctorQ

OK... guess I need to open this up to any/all types of water temperature monitoring (including all scan guages like Aeroforce, PLX, etc PLUS anyone who has installed an in-line water temp sending unit/gauge. Bottom-line: would like to know what others are experiencing in regards to when their cooling fan engages (what water temp is observed when cooling fan kicks on... then off). Thx.