2003 Nissan Altima. A/C quit & engine overheated.

Sounds like the water pump is cavitating . Replace water pump. Check coolant level also. Open the bleeder valve usually located on thermostat housing to remove air from system. close valve when coolant is present while filling. close radiator cap and top off recovery bottle to correct level. These engines are prone to overheating, do not let temp gauge get in the red.

Heater core may be clogged. Try flushing it to see if water flows through freely. Also check the heater water control valve for restrictions.

2000 Nissan Altima Heater Air Condition Section HA 76 pages Here is factory service repair manual for your vehicle . Do you know how to do testing on these system ? Automotive electrical system testing ? How to read a wiring diagram ? When hot outside is the inlet pipe to evaporator freezing up ? Do you know where this is , under the hood in the engine compartment at the fire wall . What are gauge readings , Is the compressor engaging ? Were any switches replaced ? Ambient temp. , thermal transmitter switch . pressure etc...

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

Air pockets will make the guage do that, and also cause your heat to come and go. Also, a poor radiator, as in rotting, or plugged up, will cause high temperature issues.

Locate the temp switch in the engine bay, if its a single wire just earth it and see if your gauge moves. If it does then get a new switch.

first useing a scanner or temp gun check the actual engine temp. if it is hot check for fan opperation, air lock in the cooling system water pump operation I think youll find the prblem to be the fan

On the bottom of the air unit is the lever that changes temps. It likes to fall out of place.I propped mine back with a piece of half-inch copper pipe a couple of years ago.Remove glove box then panel on front side of console to access.

It sounds like the fix is a simple one. Just change the thermostat. If you don't know how to do this go to an auto zone or similar auto parts store and they will assist you. good luck and please rate my answer.

My 2005 Nissan Sentra 1.8s with 55,000 mi. blows cold air from the heater. Coolant not circulating in engine. Lower hose stays cool to touch. Both heater hoses cold. Changed thermostat - didn't fix it. Coolant not leaking or dirty. None in oil - no oil in radiator. Changed worn water pump belt - pump spins freely with no noise or resistance. Cooling fans come on after warm-up. Temperature gauge stays in normal range then jumps to hot and back again. Coolant good to 10 below - didn't freeze here yet. No other problems or repairs to car. Afraid to drive and make worse. Help!