Ok, here we go. When I start my Elantra, the A/C works just fine. As the engine heats up, the A/C stops working. Under normal operating conditions, the needle on the temp guage stays around the middle mark, and now it jumps up just below the "H", but not redlining. It does this with, and without the A/C on(A/C just blows out warm air anyway at this point). All signs point to the thermostat, but the A/C problem confuses me. Also, if I turn the heat on, the temp goes back to normal, or close to. Please advise!!!!!!

Edit: Im suprised that the heater takes that much heat away from the engine. I wouldn't think it would make that much of a difference.

 

I'm thinking thermostat too. If not, it could be something really serious like a leak or cracked head or something. I don't mean to scare you, but I had a Plymouth Sundance years ago that behaved like that and it turned out to be a cracked head.

First step, though, is the thermostat.

 

ok first check the radiator is full (do not remove radiator cap when hot) then just leave engine to idle until needle on gauge reaches just above half way then the radiator fan should cut in at the same time check you dont have any leaks. if the fan doesnt come on you may have a fault with either coolant temp sensor, or the fan itself if it does come on then yes i would be looking at either thermostat or radiator blokage.

 

Thanks for the feedback. The fans do kick on, and the radiator has fluid, with no leaks. I guess i'll go buy a thermostat then and swap it out. Hopefully that will fix the problem.

 

while your changing the thermostat it might be worth changing the radiator cap as well......just in case

 

I would go with replacing the t-stat first. On some models if the computer sees the temp too high it will not allow the ac to come on to not add to more over heating

 

Your problem is you water pump, If you say the radiatop is full it means that the water is not been transmitted to the engine fast enough if any at all, what cause this is the impellars located within the pump erode's during time, this is caused by lime scale which causes metal fatigue.
About the A/C cutting off this is programed this way once the temp gauge rises.