2007 Shelby GT coolant fans not working


New Member
Jul 9, 2011
2007 Shelby GT coolant fans not working

I'm new to the forum. I have a 2007 Shelby GT (4.6L) with 20K miles and its bone stock from the factory. The temperature gauge goes up past the normal range if the car sits idling or if the car is driven slow. The coolant fan does not work in low speed or high speed. The temperature gauge runs in the mid point of the gauge while driving the car at highway speeds. I checked the main 40 amp fuse and its good (used an ohm meter) and I checked with a 12V test light and there is power to the fuse terminal in the fuse box. I next checked the high speed fan relay and its good with 12V to two of the 4 fuse panel terminals. I checked the low speed fan relay with the same results. Next I disconnected the harness plug going to the electric fan where the resistor is and jumped 12 v from the battery directly to the fan motor wires. Needless to say the radiator reservoir tank is full to the correct level of anti-freeze. The fan turned normally in low and high speed when direct 12V from the battery. So it stands to reason that the only two other problems are either the cylinder head temperature sending unit or the PCM is not sending out the information for the fans to turn on. Logically if the cylinder head temperature sending unit was bad then it wouldn't give an accurate reading at my instrument cluster temperature gauge (right ?). Today I intentionally let it idle in my driveway and let the temp gauge needle go just past normal into the high range then used a high end non contact infrared thermometer (made by Fluke) and I got readings of the engine block temp in the 230 to the 235 range shortly after shutting the engine down to make sure it didn't get too hot. I have never allowed it to seriously overheat by shutting it down when it approached the high end of the normal range. Never any steam or usual indications of serious overheating. Coolant level always normal. I have also noticed that the air conditioner pump will cycle every few seconds with the AC air coming out of the dash intermittent cold then warm then cold again, warm again. Today I was supposed to have an OBDII diagnostic scanner (not just a code reader) on the car but the guy forgot to bring it home from work. If the scanner triggers the coolant system check and the fan runs then I will know its not a wiring issue. I did check the wiring connectors and they were clean with no oxidation. I did put dielectric grease in the two fan plugs to eliminate any corrosion problems down the road.

Anway, I'm STUMPED at this point. I would appreciate anyone sharing their knowledge with me about this fan problem.

A little added info - I recently retired after 40 years as a full time professional auto bodyman and automotive painter. I ran my own shop for the last 26 years. I still have all my tools and a nice shop set up at home where I have a well equipped 28' x 40' heated and air conditioned garage/shop to work in. I do most of my own mechanical work but if I think I'm getting into something beyond my abilities I pay a professional. The local for dealer has been swamped all week because of the holiday week end last week and couldn't get me in. At this point the fan problem has turned into a challenge for me to get it straightened out before I have to take it a dealer service department.

again - any help will be appreciated.
  • Sponsors(?)

StangNet created a new car social app called knowmoto! Add your Mustang or post a photo in the knowmoto app and enter for a chance at a $100 gift card from LMR. Click the LMR Logo for more about the knowmoto Mega Thread!