My air conditioner cooling coils get frozen approx\.after 2 hrs of running i have showed it to the service boy they first serviced filled gas and even changed the fan motor. but still the problem remains the same .

Did the system freeze up? How old is it ? What type of filters are you using ie. Pleated or plain fiberglass. Did the technician look at the indoor coil to see if it was dirty. What is the temperature outside?

If you have serviced the air conditioner such as cleaning the condenser coil, changing the filter, cleaning the evaporator coil and checking the refrigerant, you have done about all you can do. Most air conditioners can cool up to a 30 degree differential. If its 100 outside most units will be able to maintain approx. 70 degrees. It also depends on how tight the home construction is as well. Find out if you have ample enough insulation in the attic. This always makes a good difference. Also, is there insulation in the walls and how tight are the windows? In the middle of summer all depending what the weather is like, most air cond's are running at their peak. If you have not cleaned the outdoor condenser coil with a hose and a sprayer, you might do so. Turn the power to the unit off first. Also, have the refrigerant checked. Hope this helps.

Please understand first, air conditioning system not only cooling the area but also removing the heat. If heat in the room stays constantly, even 24 hrs running a/c couldn't cool the room.
Now, why the a/c could not cool the room or remove the heat from the room.
Check air filter, evaporator coil and blower wheel for clean. If not service the unit immediately. And also check indoor fan motor rpm. If rpm is low, replace fan capacitor. Check for gas pressure to confirm no leak or running with short of gas. It's advisable to service both indoor and out door once in 6 months at least. Otherwise, your electric bill will kill you lot. Thanks.

service and checked the gas you see ice is coming or not on cooling coil

Most common reason for unit freezing up is lack of air across the evaporator coil (where cold air comes from), usually because the filter and or coil is dirty. Check the filter - wash if it needs it and make sure coil is clean. Brush with a brush or use fingers to remove matted dirt/hair.

A less likely reason is 'low on refrigerant,' and unless you know how to install a service valve and charge an air conditioner (along with finding the leak) you will need to call a Service Tech.

hope this helps

Turn off your A/C and put your fan switch in ON or FAN. Run the fan only for approx 3 hours. Check your air filter and clean/replace as necessary. Also check your evaporator coil and clean if necessary. It is possible that your evaporator coil is frozen up from a dirty filter or coil. If it continues to be a problem, you probably have a refrigerant problem which will require a certified service technician to address. Try taking care of the filter and coil first. :-)

If the coil was frozen over it tells me there is a different problem. If the coil is frozen over try this. turn the circulating fan to the on position and the sir conditioning to off . Let it run this way for 1-2 hours to melt the ice and re-establish the air circulation. Then turn the a/c back to the cool mode and see how it performs.

Lower temperatures during evening and night conditions can cause coils to freeze over. Running you A/C with the fan in the on position generally takes care of this problem when you are cooling.

Four things cause icing up:
( 1 ) Is your filter clean? dirty filter blocks air flow causing iceing up. replace filter
( 2 ) Do you hear the Indoor fan running? If the fans not running the unit ices up. Check Capacitor to fan if good.
Bad fan motor... replace fan motor and cap. If both good
( 3 ) Check Air Handler evap coil if dirty and or clogged, restricts air flow causing unit to ice up. Use toilet brush to clean.
This is always a big possibility if you have pets.
( 4 ) If the above are not present then you are low on refrigerant.
Low refrigerant will cause icing up because the gas does not flash properly. This will require a service tech.
refrigerant leaks can be as simple as a loose cap on the king valve, leaking schrader core, to coil leak.
Have the service tech show you the leak. If it is in a copper line it can be fixed. If the system is over 10 years old limit the amount you want to spend. 10 years is the standard life expectantcy anymore. Good luck

If the running capacitor is bad the compressor will draw above average amperage and the overload protector will cycle the compressor off. You should take it in for service.

Check the indoor fins and air filter if dirty, so if its dirty cleaning is needed specially the indoor fins it should not be block with dirts. But if it is clean then you need a qualified technician it may need additional gas.