Help! Overheating or not that is the question

Hi, Thanks in advance to anybody that can help me solve this mystery. I have a 2003 1.8 Turbo with 39,000 miles on it.My red temp light came on flashing and beeping.(It does not stay on, it keeps going on and off ) I checked all the fluids and that seemed to be ok. I have checked the fuses and brought it in to a mechanic. He checked the waterpump and could not recreate the problem. He was sure it is the temp sensor. I ordered the part and I am still waiting for it. I kept driving my car and all of a sudden my airconditioning is blowing hot air instead of cold air. When I checked this morning there was no coolant left in my radiator, where did it go I could not find any leaks? Any ideas :screwy:

I purchased a 2000 VW Beetle with the 2.0l engine and I was told that everyonce in awhile the red coolant light comes on and beeps when the engine is started. I haven't seen the coolant gone yet but she experiences the red coolant light vs the blue one. :screwy: :banghead: