I have a 2001 F -150 V8 TRITON 4X4. When i purchased the truck about 8 months ago, i did not know the air cond. was not working. I took it to a local mechanic to fix the air and he said it had no gas in it and this was not allowing the compressor to run. He also said I needed a new blendair switch. He flushed out the system and gassed it up. He did not fix the blend air switch but said he opened it to air cond. mode. He said I would have to bring it back before winter to replace the blendair or I would have no heat. With all this said since this work has been done my battery has a drain on it that causes it to go dead over night. I have to boost it off and then it will recharge itself when I drive it. I took it back to the mechanic and he unhooked every thing associated with the air and the drain was still there. He also checked the alternaitor exc. Still could not find the drain on the battery. I noticed another thing when I drive the truck with out the air on it will freeze up on the tubing and around the compressor. When I turn the air on it will defrost itself and melt. Any help will be greatly appreciated.

 

sounds like you or your mechanic need to do a parasitic draw test on your battery. being a mechanic he should know to do that already.i do this at work and then start by unplugging fuses and watch my multimeter to see if the amp draw goes away that way whatever fuse you pull makes the draw go away you know which circuit you have a problem with.

do you have any aftermarket electronic accessories?electric brake controller? CB radio? scanner? anything plugged into the trailer wiring? start by unplugging those while you do the draw test. any dome lights left on? do the lights outside the cab by the third brake light stay on when the doors are shut?