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Juan Crespo
Juan Crespo, Tech Trainer
Category: Ford
Satisfied Customers: 1526
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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I have a 07 mustang v6. It was over heating on my wife. The

Customer Question

I have a 07 mustang v6. It was over heating on my wife. The temp gauge will go to the half way point without the fan turning on. Also when I turn on the Ac, even for just a brief second, the fan will work and stay on. I've replaced the engine coolant temp sensor and tried replacing the high and low speed fan relays. Any help is greatly appreciated, thanks.
Submitted: 1 year ago.
Category: Ford
Expert:  Eric replied 1 year ago.
HI,Ok, I need to get the vin number of the vehicle so that I can pull the schematics for the cooling fan system
Customer: replied 1 year ago.
Customer: replied 1 year ago.
Any luck?
Expert:  Eric replied 1 year ago.
HI,sorry for the delay. I am having internet router problems and just now got back online but dont know how long I will have access so I will release this for other experts to help
Expert:  Juan Crespo replied 1 year ago.
Hi there.The fan motor relays are controlled by the onboard computer (PCM) based on signals it gets from the engine coolant temperature (ECT) sensor and the A/C pressure sensor, so any malfunction on the system should have set a code - most auto parts retailers will do the PCM scan free of charge.Is coolant level OK? Any visible leaks? Have you done any work to the cooling system lately? Is the Check Engine Light on?
Customer: replied 1 year ago.
Coolant good, no leaks, and no recent work. More to come on the code
Expert:  Juan Crespo replied 1 year ago.
Looking forward to it.Best Regards.
Customer: replied 1 year ago.
Expert:  Juan Crespo replied 1 year ago.
OK. P0128 usually sets when there is a problem with the thermostat not closing or opening correctly - which would also account for the symptoms you described. Replacing the thermostat should take care of this issue.Best Regards.
Customer: replied 1 year ago.
Except for the fan not engaging, once I make it turn on by playing with the Ac it works perfectly. I'll replace the thermostat and let you know if it works.
Expert:  Juan Crespo replied 1 year ago.
It's all sort of connected; engine heat makes the coolant hot which makes the thermostat open up; then as the hot coolant flows, the ECT reacts to the high temperature and sends the pertinent signal to the PCM, which then energizes the fan relay to make the fan motor turn and pull the heat away from the coolant circulating through the radiator and the cycle begins again. As it is, the PCM has deemed the ECT signal unreliable and has set a code. Turning the A/C on triggers the default function which is FAN ON.Don't forget to erase the code after thermostat replacement so the PCM can again run the monitor that allows it to check how the system is working.Best Regards.