99 Acura TL. The Temp gauge only goes up when idling for a long time. It dosent matter if AC is on or off. Many times i catch The needle going up and i quickly turn the car off. Today I was able to pop the hood and see whats going on. My passanger side fan was no on!!!!!!!!!!!

Does anyone know why? All my fuses are good. Im thinking its a relay, but which one?

 

passenger side fan is active with the AC on, and if the temp goes way hot it may be a secondary--- Im not certain on that part
The temp should be rock steady - only the driver side fan coming on and off would tell you the engine is even running at idle!

When the temp starts to climb and you shut the engine off- it makes the problem worse- now there is NO flow of coolant- before at tleast there was some with a problem
So parts get even hotter- fix this asap!!!

First thing to check= is the driver side fan working- the sensor for it is lower passenger side of radiator- the bottem of it- look for a wire- that goes bad a lot
Does the passenger side fan cone on and off with the ac control on
2nd- Is it full of coolant- check when dead cold- radiator full up to the neck- and the overflow bottle is at cold line- with the hose inside the overflow cap attached, so it goes into the bottle- those like to fall off too and the coolant cannot transfer as designed.
3rd- how is the radiator cap seal- look worn? a parts store can test its pressure holding abilty or you can just buy a new cap and thermostat- install those and probably fix the problem
4- how many miles???- supposed to replace the water pump- coolant and timing belt at 105 k miles or 7 years
Check those things out