High Pitched AC Whine on 04 explorer-mostly at higher RPM

[mdisalvo]

My 04 has 138k on it now and as far as I know the AC has never been recharged or serviced. I went on a road trip over the weekend and was running the AC fairly hard on the highway and it started making a whining/whistling type of noise that sounds like it's coming from the center of the dash/vent area. Any ideas what that might be or any troubleshooting advice so I can diagnose the culprit? Not sure if this matters but prior to this I noticed the AC was starting to blow warmer and taking longer than usual to get cold.

 

[Joe in NY]

it could be that the evaporator developed a leak and you are hearing it whistle.

Also cars are not supposed to have the AC serviced or topped up ever if they are in good shape. Only when things go wrong does it need attention.

Do the vents still blow strong ?

 

[mdisalvo]

Yea they do blow strong, I removed the blend door about 5 years ago if it matters.

 

[mdisalvo]

Well I figured it out...this is going to go down as one of the easiest fixes on here of all time. My friend had closed his vent by the window about 95% just leaving enough of it open to create a whistle noise.

Since I have this thread started I do want to ask about the AC taking longer to get cold and not quite getting as cold as it used to. Should I take it to an AC shop or wait until it completely stops blowing cold air?

 

[Joe in NY]

I've had that exact same issue haha

Probably should. When these systems get low it can allow them to freeze up the evaporator which means no air flow. But more importantly when it gets low not enough oil makes it back to the compressor and then the compressor starts to wear out and cause huge headaches in the near future.