When service was called, they did come within 4 hours but they had difficulty diagnosing the problem on a 3 year old AC system that they had installed originally and that was used on a limited basis by owners not in their unit most of the summer. After replacing a defective solenoid module the first day, the unit ran for a short time and then shut down again. There was a short in the wiring that the tech had to temporarily repair and had to come back the next day with the proper crimping tool to do a permanent repair. The charge was $482 for the repairs and although parts were supposedly covered for 10 years, the labor charge was outrageous for a 3 year old system. The fact that there was a short in the wiring implies that the original installation was not done properly and it should not have taken so long to fix. It seems to me that the tech was not as knowledgeable with this system as he should have been. I will not know how well the repair was done until I return to my unit next month to see if it is still working.