Radiator or water pump

[dfor]

2002 Nissan Maxima. 168,000 miles. Engine temp rises when the car is sitting at an idle with the ac on. Never use to do this. Turn the ac off and the heat on and the temp lowers.

Car is fine when driving down the highway. I replaced the thermostat, thinking that was the problem (not). Water pump or radiator. Thanks for any help.

[festerw]

Is the electric fan coming on when you turn the AC on? If not check the motor on the fan.

[dfor]

The electric fan in front of the radiator does come on when the AC is turned on.

Checked this morning, and after about 5 minutes, no overheating. But then again, it was only 5 min. and it's only 60 degrees outside. I was hoping that it would have been the fan, once you mentioned it.

Any other thoughts appreciated.

[Pickering Snow]

First the fan should always come on with ac to get highside pressure down thats a seprate fuction of the pcm. The Fan also will come on with the fan switch which is in the rad, when the temp hits 228 and then shuts off at 221 again another funtion of the pcm/ fan switch.

On your car since its when idling with AC on i would suspect a coolant flow issue , has the compessor loads the engine more even with the fan but the key here is some MAX cars have duel fans a pusher and a puller the pusher is sometimes hard to see. Best to check temps at both hoses when this is happening its a good way to comfirm stat issue or no circlation, both hoses should be equal temp, just be careful i use a thermo gun for doing this. Theres a poss it could be just slightly low on coolant has well dont trust whats in the overflow jug, another thing hows the ac temps in the car when its running hot is it still cold? .

There is a remote chance on a 3.0 max motor the waterpump impeller is starting to slip but its slim, i would suspect something more simple since its intermitt and only on really hot days, check rad and condensor for debris build up has well causing poor air flow threw the rad.

[dfor]

another thing hows the ac temps in the car when its running hot is it still cold? .

No cold air coming out of the AC when it is running hot.

[Pickering Snow]

No cold air coming out of the AC when it is running hot.

Well now theres a raft of poss for this is the ac overcharged, causing the compressor to build up to much high side presuure causing the compressor to drag on the engine and overheat, again it makes me wonder if the fan is spinning at correct speed, since you say it cools back off when you start driving again.

Without seeing it kinda tough but i suspect a issue with ac, fan or both.

[dfor]

Thanks Fred and festerw for the suggestions. It ended up being that the a/c condenser needed cleaning. It had a build up of dirt and debris throughout the years. Hasn't heated up since.