What is causing my car's AC to make a hissing noise?

I have a 2006 Ford Crown Victoria Police Interceptor whose HVAC system makes a hissing noise when I turn it off. When I put it on normal AC, Vent, or any other setting; it goes away. But if I put it on Max AC or turn it Off, it makes a hissing noise. It sounds as if it is running, but it is not when I have it switched off. It blows cold and hot when I want it to, I just want to know what the noise is. Also: it only happens when the car is running. If I turn the key to the #2 position before the ignition, it doesn't make the noise unless the engine is running. Any idea as to what may be causing this?

This vehicle uses vacuum motors to change the "modes" from heat to defrost to panel and to change recirculate to fresh. The vacuum system also has a vacuum reservoir to store vacuum.

You've got a vacuum leak.

VACUM LEAK

  • My car is making noise when I turn the wheel, what could be causing it? I put power steering fluid in and double checked it to make sure it was full, which it is. But whenever I turn the wheel it still makes a terrible noise, i almost want to not drive it anymore just because of that noise. Anyone have an idea what it could be? Is it the power steering pump maybe? If it helps, my car is a 2001 Ford Mustang, FWD. The noise is coming from the front of the car.
  • Hissing coming from under my ford 2e250? Hissing sound coming from my ford e250? There's a disconnected hose right under the passenger side, underneath. It has 3 holes and stops when I out my finder over then. What could it be?
  • What's causing my car to over heat? I have a 02 Ford Focus. EVERYTIME we drive it the dang thing overheats and when it starts to go off of course the air blows hot. However the thermostat will go back down and the cool air will come back on again SOMETIMES white driving. I can also shut car right off sometimes and start it back up a few mins later and its fine, It just goes up and down on its own. All the right amount of new fluids and all that are in the car. We had a new fan put in also and its still not helping.
  • Noise works, but when I push it, it also makes a clicking/rattling noise? I have a 2012 Ford Focus, and while the horn works, and sounds (as it normally does), when I press it, it also makes a weird clicking/rattling noise (also kinda like a jingle sound - hard to describe). It sounds as if it's coming from behind the center console/under the center console, but it's hard to tell. Any ideas what it could be? With any answers - any advice on how to fix it? Question should say HORN Works

Add Comment