I am having problems with the AC in my civic. Sometimes it works great and when it does it has about a 30 degree difference in the outside temp and the vent temp. Sometimes when you need it the most like at a red light, the vent air will just get really hot. When you start to move again it will start to cool back down. I have noticed also that the vent air will get hot sometimes while the car is running down the interstate. It almost like there is a switch that is turning the compressor on and off. Any one with any thoughts
Steve

 

it could be the relay. have you made sure the a/c fan is working? that would make the air get hot at a stoplight.

 

yeah check the fan, also it could need a recharge or a something is blocking the vent(s), doubt its that tho.

 

I agree. Make sure that the condenser fan runs. Also check whether the A/C compressor belt is loose.

 

When it is not cooling, pull over and check that the fan is running and the compressor is engaged (front plate is spinning). If the fan runs but the compressor is not engaged, check that you have 12 volts to the clutch wire on the compressor.

If it is getting power but not engaging, the clutch gap is probably too wide. That causes the clutch to not engage every time, especially when it is hot under the hood. It can be remedied by taking the shaft nut and the front plate off and removing some of the shim washers from the shaft. This can be done while the compressor still installed and the system remains charged.

You may be tempted to test the clutch by jumping 12 volts from the battery right to the compressor. Do not do this with the engine running, you have bypassed all the safety features and with the fan not running, the pressure will rise out of control. It is OK to do it with the engine stopped.