Air Conditioning - Trane XE 1000 leaking fluid

I have a Trane XE 1000 a/c unit in my house, which is probably about 18 years old (???). When I go outside to look at the fan/motor unit water leaks out of the back of the unit onto the cement pad it sits on. It has always done this and I was told by a repairman that it was perfectly normal for it to do so. There is also a pipe, however, that sticks out from the side of the house at the second floor level above the outside fan/motor unit. It's an open elbow pipe that points towards the ground. The same repairman told me at the time that if I ever saw water/fluid leaking from the elbow pipe, then it meant trouble. About three days ago, i noticed fluid (water?) leaking from the outside elbow pipe. As far as I know, it has never done this before. My a/c unit is presently functioning.

My questions are: 1) what does the pipe connect to? 2) what is leaking out of it? 3) is my unit in trouble? 4) if so, what do I need to do to repair it? 5) how much will it cost me? 6) is it something that I can do myself?
I appreciate any and all comments/suggestions.

Thanks,
Planview

the water(not flowing but wet) out of the back or around the condenser is normal after rains or on a real humid day..might want to check it out inside for leaves and dirt hose it out for the season.the pipe from the house should be the condensate from the furnace air handler..BUT if the air handler is in the attic and you have a metal pan under the unit up there this is possibly the emergency overflow pan and needs to be checked.the unit itself has a dedicated trapping set up with white PVC that always drains water the drops of humidity collected during a cooling run....and that pipe also runs out side.if you don't have that secondary pan under the unit in the attic that pipe is your condensate and water out of it is normal(pencil round water flow).if you don't see water coming out during a warm day of cooling there might be a blockage.big question :confused:to define that mystery pipe where is your air handler when your standing out by the condenser with the fan and the compresser?in the basement or abovre you in the attic?

Thanks for your reply sminker! It would be in the attic. I'll pop up there and check it out to see if there's a secondary pan...

Yes you should have called your HVAC company the day you saw the leak. Main drain line is blocked, Darin pan gone, or you have a block of Ice in the unit. Call before your ceiling gets wet.