I have a 10 year old air conditionerthat freezes up and i can't find the drain tube in it.

The defrost cycle is not working. After a predetermined number of hours of compressor running time, a timer actuates the defrost cycle, which stops the compressor and turns on a heating element to melt the ice. Either the timer or heating element is not working. Also, make sure the melted ice water is actually draining and not re-freezing.

The problem is the drain is clogged. Remove the back panel in your freezer and at the bottom of the evaporator coil you will see a hole about ½" in diameter this is the drain tube. Try using a turkey baster to flush out the drain tube. You might need to use some warm water to melt the ice and then run a wire being very careful not to puncture the hose and run it down the tube to free up the drain. This tube travel down to the bottom of your refrigerator to a pan sometimes located on top of the compressor or somewhere else down there. It collects the water there to evaporate. After cleaning mix a 50 -50 solution of baking soda and water and run some down the drain tube this should help prevent future clogs. You can enter your model # at www.appliancehelponline.com for a diagram or illustration of your refrigerator. Not all models are available.

sounds like the evap coil is freezing. it is frozen if you have low air flow. check the lines and see if your suction line is freezing. also check your filter. if you think your drain line is clogged cut the line and blow out with an air compressor or nitrogen. all you should need to fix the line would be a 3/4 in coupling or a union. hope this helps

Good day,
If it happens that infrequently then nothing is technically broken.
More of a design, engineering issue.
Check this. It's for a freezer but the rules are the same.

http://www.fixya.com/support/t4759036-upright_freezer_not_drain

The condensate drain must be clear, otherwise there will be a lot of moisture in the coil area. If there is not enough air flow the coil can freeze -check filters are claen and fan is working properly.

HI .did you pull the fridge, away from the wall, and clean out the drain tube ,at the back. if not pull fridge away from wall, find the drain tube, and clean. thanks the appliance doc

check to see if the fan running first, if yes than you may be losing freon. if not , try a new fan motor

Make sure the condensate drain is clean and clear of any debris. With the indoor unit off, Remove the inspection panel and pour a gallon mixture of 10% Bleach to Water solution in the drain pan. Do not overflow the pan but check to make sure there is flow to the outside or drain. Clean out the drain hose if you have to. A freezing coil is a sign of either not enough air going across it or not enough charge in the system. Check to make sure all of the return air vents as well as supply vents are in full open and unrestricted. If they are, you will need to have the charge checked. If this turns out good, have your technician install an anti-freeze kit. This kit will temporarly turn off the compressor unit for a short period when the sensor in the kit experiences a freezing condition. Then after a bit, it will turn on the compressor. It may not cool as much as it was, but it may get you thru. Good Luck!

Seems to be a common problem with these units. You can get a drain tube heater ( got mine from an online refrigerator parts distributor), though may not totally solve problem. Some suggest running a copper wire through tube - supposed to conduct just enough heat to keep tube from freezing.

drain line is blocked check bottom tray if is collecting water if not drain line blocked