When I turn on the heat or AC the compressor makes a THUD sound every time it engages. I've never had a vehicles, new or old that did this. Only have 19k miles. Haven't gone out to try other Rangers to see if this is common.

 

Im guessing you haven't run the a/c in awile mine did the same thing on a 2001 B4000 it helps to run it at least once a week for about ten minutes to keep everything in check

 

It does it even when I've used the AC for hours.

 

beats me then I hope its still under warranty

 

There is nothing wrong with it, you have described normal operating sounds; myself and everyone else that I know that has a late model Ranger experiences this. If after reading this you are still concerned, call your service manager and have a quick talk with him.

 

The other day mine was cycling on and off every minute or so and I thought something was wrong with it. I asked one of my techs about it when I got back and he explained that since I had it on defrost it was just cycling to keep the compressor in running condition throughout the cold weather.
I had never heard the noise except with the A/C but I expected it then. I never had a vehicle with A/C before (well working A/C that is) so it was a revelation. Made perfect sense once he explained it.

 

These newer rangers will turn the A/C on if the **** is on any position EXCEPT for OFF, VENT, and FLOOR. (I don't understand why VENT/FLOOR combo would kick on the A/C, but whatever haha)

I have a 2000 B3000 and the compressor thuds like crazy anytime it engages. Just the nature of the beast. I've evac'ed/recharged my a/c and added an aftermarket (BG) refrigerant oil to it trying to quiet it down, and it did help a little, but it's still very noticeable. Pressures look great, and it blows very, very cold... just have that dang thud.

I think it's just the design of the compressor. These trucks weren't made to be smooth... or quiet... or even comfortable (although they DO ride better than most other trucks out there).. they are supposed to simply be a tough li'l pickup.

 

Check the belt on the air compressor.

 

My 01 has always done that. I had it checked, and they said it was normal.

 

The problem is that clutch on your a/c compressor has to wide of gap, this can be adjusted using shims that look like 1/4" wahers that are diffrent size and thicknes that you can buy at any parts store. Since this is under warranty you should take this back to your dealer. This is not normal sounding, to wide of gap and it will make aloud thud and in time will cause premature wear on clutch to small of gap and will cause the clutch to not completly release.I had the same problem with my 2000 ranger it was out of warrant so I fixed it my self.