Why is my ac not coming on?

As long as the a/c clutch plate is not engaging and the clutch bearing is not making noise while rotating, you should not have any problem.

my autodata belt book shows 18 hyundai belt set ups 1992 to2012 and only one that runs a special belt for the ac
for all the rest the ac pulley is required as the belt runs around it to drive power steering, alternator , water pump
test the ac pulley by removing the belt( after drawing a diagram of how it runs ) and trying to spin the pulley
if it is as you say have a mobile mechanic/ ac mechanic come and remove the pulley and replace the bearing ( about 1 1/2 hour and $20.00 for the bearing
if the pulley spins then disconnect the wire to the compressor so that the clutch is not engaged for the compressor

Air conditioner clutch is going bad and needs to be replaced.

Knowing make model and year would help. Most newer vehicles, 2000 and newer, will adjust the idle control up to compensate for the compressor engaging. Possible there is an issue in the idle air control valve or electrical circuit.

is your car at an idle when the a/c is engaged it takes power to run this circuit your engine will slow down. most cars have a sensor that will increase you idle when a/c is engaged. this also compensates for the added drain on the alternator

the belt driven aircondisioning unit is located under the hood. there are usualy metal lines coming off of it and one should have a valve in it ...looks like a tire,air valve. when car is running, turn the AC on. the unit has a two part clutch that the belt will turn. when the AC is off...the pump or compressor will engage and the hole belt driven piece will rotate when the AC button is on. , when it is off....or not getting power to the clutch , the pully will spinn but the inside clutch will not.

iff the unit engages and turns when the AC is turned on, and still blows hot air, then you may have a leak in your refrigerant line. iff it dosnt engage, then check your fuses .if everything is good to go..then it is mostlikly a vacume issue located in the dash behind the AC switch and display that moves the vent from hot to cold....

Ok..that is a strange one.. I am going to hazard a guess and suggest you look to the AC compressor.

When you run the defroster the ac compressor comes on..typically whenever the outside temp is above 40 degrees.. the ac compressor kicks in to dry out air inside.

Often when it rains.. the windows fog.. you turn on the defrost.. the ac compressor tries to come on.. and.. there ya go.. rather there your serpentine belt goes.

Several things could cause this.. worn belt.. failing belt tension-er... or failing ac compressor..

If the ac compressor is frozen meaing it will not turn..when the electric clutch on the front engages.. it would cause the pulley to stop turning.. and the belt would have a hard time staying on a non rotating part.

Or if the belt tension-er is bad..or the belt is worn.. when the additional load of the compressor kicks in.. it jumps off.

Finally it could be a combination of all three..


Best of luck..

Unplug the ac compressor,it comes on when the defrost is turned on,you have a ac compressor clutch going bad,or the ac compressor itself is bad.

Are you sure the noise is coming from the compressor and not the belt tensioner or other accessories, when you turn the ac on it put more of a load on the engine. If not since the compressor was changed twice was it properly oiled and the clutch turned manually to insure proper lubrication. I am hoping if it is the compressor that the reciever dryer and expansion valve was changed and the ac system was flushed well, to insure no contamination, or blockage damaging the new compressor.

if the compressor was locked up the drive belt would come of when u engage the AC compressor, your problem is most likely a low charge