Why does the A/C in my car stop working when the car stops moving?

Every time I sit at a stop light, the temperature in my engine starts rising. Additionally, if I sit there long enough (as often happens in rush-hour, downtown traffic), my air starts blowing hot. Then, when I speed up again, the engine cools down, the temperature gauge lowers and the air gets cool again. It runs cold when the car is moving. I have had the entire A/C replaced and the hose which connects my coolant tank to my radiator has fallen off, and put back on a few times. So, why does my car keep getting hot? Why does the air keep getting hot along with it? Is there a correlation between the two?

Why does the A/C in my car stop working when the car stops moving?
There might be a correlation between the two, but probably not. Check to see if your water pump or radiator is leeking. Check if the anti-freeze is leaking. Your cooling thermostat could be broken. The radiator fan motor could also be broken. Another possibility is the cooling pump could be bad.
Reply:Your electric fan on the radiator is not working.......Nothing else.


Air needs to flow through the radiator to remove the heat from it.


If you're stopped, and your electric fan is not working, air will not flow through it untill you start moving the car.
Reply:Engine temp is related to the following:





Radiator, water pump, fluid level, thermostat





Check for leaks, top fluid, replace parts if needed.





A/C - Freon levels (if its an older car, it may use the older freon which WILL require some replacement parts to fix)





At a stop light, the engine isn't running as fast and the A/C will be working harder to cool your car, so the air won't be as cold as when your moving. The same thing happens in reverse for your engine coolant, the faster you go the cooler the engine temp.
Reply:Rolling along forces outside air to flow thru the radiator, cooling the water and assisted with the engine fan to cool the engine. When you stop, heat builds up in the engine compartment while its running and the air conditioner compressor also heats up, thus no cool air. The compressor is not connected to the radiator water. That hose to the coolant tank to the radiator really doesn't help as the coolant tank is only a reservoir for the coolant only. Remedy? (a) get a larger radiator for more water capacity to cool the engine or have the present radiator flushed out. (b) install an electric engine fan to assist the main fan cool the engine. (c) check the opening of the grill to see if there is any obstructions and to see if the radiator is not clogged with dead bugs, debris or other trash preventing the engine to "breathe". (d) keep the coolant/water ratio at proper level. You could also install ram air scoops but that may be too much. Hope that helps.
Reply:It runs more efficient when the car is moving because the engine can generate more electricity. but if you say it blows hot air must be something wrong. Check your alternator
Reply:you have a bad electric cooling fan motor or a problem with the controls or wiring to it. this fan cools the radiator and a/c condenser. if it does not work you will get the exact symptoms that you described.


if your car does not have electric cooling fan(s), the problem will be the fan clutch for the radiator fan.
Reply:did they replace the condenser,in front of the radiator? and also for the heating,the condenser could have stuff like leaves and debri stopping the air flow to the radiator.
Reply:Your radiator is probably going bad. I would also look at the serpentine belt. It powers alot of the things under your hood including AC, water pump and alternator.