Saturday, October 15, 2011

Car AC Blows Warm Air ?

There are many possibilities for Car AC blowing warm Air.
This problem is very common and noticed by Many cars and Truck users.

The possibilities for this problem are:---
1) Refrigerant is getting lost on AC system.
2) Compressor not engaging when  A/C is turned ON.
3) There is obstruction / clog in the system.
4) The blend air door  is stuck inside the HVAC unit.

The Blend door getting stuck problem is very much noticed.The blend door actually moves as per you set for heat and cold.If the blend door is stuck up in HEAT mode,then no air will pass through evaporator and warm air will blow.

For troubleshooting the problem in your case.You have to check all the possibilities mentioned.

You can start by inspecting the function/ working of compressor.

Is the compressor engaging when you turn ON the AC in your car.

If you notice that compressor is engaging, this confirms that AC is working properly.This also confirms that there is enough refrigerant in your system.So if compressor is working,then the problem is towards blend door motor.The Blend door motor needs to be replaced.Its located in the HVAC unit.The HVAC unit has to be taken out,to replace blend door controlling motor.
This is not a easy job.Its time consuming job.

BUT,NOW think on the other side.If your compressor is not working.
When you turn ON AC,the compressor is not engaging,then.
In that case there are two possibilities.
1) The compressor itself is faulty.
2) The problem is related to AC clutch.
To confirm this you will have to do a simple jump wire test.

In this test you connect compressor clutch wire directly to the battery.Please use fused jumper wire,so if fuse blows,then you know that clutch is problem.
Now if the compressor runs while you jump compressor clutch wire,then its confirmed that compressor is running and working.And the problem is with clutch related components.The clutch related components are bad A/C compressor clutch relay or a bad clutch cycling switch or pressure switch.

But if compressor is  running when you jump the compressor clutch ,but compressor is not engaging,then problem is with compressor clutch.

If the compressor clutch engages and compressor starts running but still you get no cold air then its problem of refrigerant.Its low or getting leaked.AC pressure test needs to be done.


You will have to get AC pressure gauge testes,to check refrigerant in the system.
Connect the pressure gauge tester to the high port of the AC.
There are to ports,high port and low port.The high pressure port is located between the compressor and the condenser in the front of the engine compartment.If the pressure is checked low then,AC compressor will not engage.Because low pressure safety switch  will not trip to engage the compressor.If the refrigerant is checked low, then AC refrigerant has to be recharged.The air in the system has to be purged out,before filling/charging AC system with refrigerant.The refrigerant should not be overfilled or under-filled.If you dont know exact refrigerant capacity of refrigerant required in your car AC system,then get detail from cars manual or from local car AC repair service store or from local HVAC technician.

To do refrigerant pressure test,the procedure is as follows:---
Click the link below:---

But if the refrigerant is checked ok and compression is also running properly,and still the AC is not cooling and just blowing warm air,then its blockage issue.

The dirt clog obstructed in the orifice tube.The orifice tube is located in the high pressure hose between the condenser in the front of the radiator, and the evaporator located in the passenger compartment.Due to the clog in orifice tube, the refrigerant will not pass freely in the system.In that case the orifice tube needs to be cleaned,serviced.

If you see frost or condensation on the high pressure line from the condenser to the evaporator and AC is blowing warm air.You get no cool air from any vents, then problem is blend door .The door is stuck in the HEAT position, or possibly a badly clogged cabin air filter that is restricting airflow.You will have to manually take apart the dash and inspect the movement of blend door and see.If you notice that door moves freely and its not stuck,then problem is climate control module.

This procedure should help.

For more car problems help.
This are best blog sites to refer:---