So, a couple weeks ago my wife and I have been having problems with our 2004 Honda Accord 3.0 Couple. The main issue is the car overheating (or seeming to overheat). Here is everything I know.

When at highway speeds with a/c on, the car temp starts going up after a bit. If you stop the car and turn off a/c, the car runs at a normal temp. Also, just now I let my car idle with the a/c on full, for about 1.5hrs. When I check on car, it was about 3/4 up the temp dial.

So, I turned it off for a bit. I went back out and turned it back on. I had a/c on and the temp started to go back up. I turned a/c off, and the temp started to go down a bit.

Anyone know what could be the problem? Both fans up front are running as they should be I would imagine. It is kinda hot right now as it is in the 90's today. But yeah, it seems that on a hot day with a/c on, the car will overheat even at idle. I would have thought a 2004 wouldn't have such overheating problems. There is plenty of coolant in the system and no visible leaks.

 

From your description, the thermostat is likely not opening fully and causing the temperature to over-run. A new thermostat is indicated.

It is also possible the temp sensor is not sensing the correct temperature. If you can buy or borrow a infrared temp sensor, you can check that temps are going over 195F (overheating). If temps are normal and gauge is in overheat range, the sensor may be faulty.

good luck