I’ve begun hearing a strange noise when the ac or defogger is in use. It makes a ssshhhhh sound. Then as I was driving white smoke began coming out of the vents. Before I take to mechanic can anyone give me some info on what could be wrong? I drive a 2005 pontiac vibe
The sound is likely a leak. Three things can leak in there. Coolant (the heater core or hoses) Refrigerant from the A/C or air from the blend doors that are operated on a vacuum. The cheapest would likely be the blend door, but it would not make the smoke. Either of the other two could make the smoke. Does the smoke smell sweet?
Your description of the hissing sound is too vague to be of any use. I won’t even try to guess.
The “white smoke” that you sometimes see is no doubt just water vapor. It is like seeing your breath on a cold day. It occurs whenever warm, moist air meets cold, dry air. It is harmless and it even provides assurance that your A/C is working strongly.
Since you have no real complaints about your A/C’s operation you might even change your mind about going for service.