Car overheating especially when a/c is on

my 2002 Ford Taurus (240,00K miles) is overheating when the a/c is on and the car is in gear. The mrchanic or I can leave the car idle with the a/c on for an hour or more without it overheating but as soon as I drive away, the gauge starts to rise. I’ve changed the 2 fan relays in the front fuse compartment and had the thermostat changed last year. Any ideas? With the temps over 100 and leather seats, NYC is not a fun place to drive lately. Thanks in advance

The problem might be caused from a restricted radiator. With that many miles on the vehicle it isn’t unheard of.

Take it to a shop that has an infrared thermal gun. And ask that they scan the radiator with this to determine if there are any cold spots.


Once you start moving, the transmission fluid gets hot and adds heat to the radiator - sounds like more heat than it can dissipate - Tester is probably right. If it doesn’t overheat sitting, the fans are fine, they don’t do much when you are moving

I sound like an old record, have a coolant pressure test in addition to a radiator cap test done. Summer is cooling posts, winter is battery posts, I wish the web lackies could provide a link we could point users to for general problems like this.

“as soon as,” isn’t quite definite enough. From the moment you move away from totally stopped do you drive 10 feet, 10 blocks, 10 minutes, or 10 miles before the temperature is HOT? And under the same circumstances what occurs with the AC off? Does your mechanic have a proper scan tool? If so the temperature from the ECU can be monitored and compared to the dash gauge.