It is my experience that the A/C compressors should only run when the HVAC is set to A/C or Defrost.

My 2005 Ranger Edge runs no matter where the HVAC switch is set, except the off position.

Is it the design intent for the compressor to run in all modes except Off?

Also, every time the clutch kicks in, it sounds like a loud thud inside the cab. Is this normal? Based on all the prior vehicles I have owned, I wouldn't expect to hear much of anything when the clutch engages. (On my previous vehicles, the only indication of the clutch engaging is the lights usually flicker...)

Any help is appreciated!

 

The A/C should run in all positions except floor, dash vent and off positions. The A/C normally should not cycle very much. It can be heard but I would call it a click more than a thud. I don't know if what you are hearing is normal.

 

Thanks for the input FX4. My 3.0L Ranger has a problem. The compressor runs in every mode except off. What you said confirms my life experiences in that the only time it should run is in A/C, AC MAX, Defrost with Floor, and Defrost Only.

Does anyone have a clue what could cause this? Is the rotary mode switch bad? Is there a body control or HVAC module that might have gone bad?

I would really like to fix this since it is only getting about 16 MPG around town.

 

In the late 1990's, early 2000's and up the AC Compressor will run in all settings except OFF.
On some it will go off in Floor only setting.

The AC compressor being on only when AC or defrost is selected was correct on older models but no longer applies.

The computer runs the AC compressor now, the climate control switch "tells" computer what driver has selected but no longer directly controls the AC compressor like it once did.

There will be an AC Clutch relay in the engine fuse box that can be pulled out or, of course, the wires on the compressor clutch can be pulled off, to stop compressor from cycling.

But you would lose fast Defrost time

You may want to check with a Ford Dealer to see if there is a computer(PCM) software update for your model year and if it includes the older settings that only had compressor operating in the "old way".
There are many complaints about this constant AC cycling.

 

Ron, my 02 does not run the A/C compressor in dash vent position. The only difference between A/C position and dash vent position is the A/C compressor does run in the A/C position. There would be no point in having the dash vent position if the A/C ran in that position also. I don't think my climate control switch is unique because I have seen many others that operate the same way. It sounds like that is what Marty has experienced also. Maybe later models operate as you described but I don't have any experience with them.

The only time my A/C compressor started cycling a lot is when it was low on Freon. Having it recharged solved the problem. Another time the A/C compressor seemed to be intermittent and irregular in cycling and replacing the pressure cycling switch resolved that.

 

It is totally up to computer software now as to when AC compressor is used, so it can certainly vary by model year.

Yes, if you are low on "Freon" the low pressure switch will open as compressor sucks out Freon, and then close again as more Freon flows back in to low pressure side.
So compressor cycles on and off.

 

FX4 is right, my A/C compressor does not run if the mode selector is in dash vent only position. I haven't checked the floor vent only position yet, but I believe FX4 knows what he is talking about.

Yesterday I was driving to work, with the dash only mode and The interior of the windows started to get lightly fogged up. It is apparent these small interiors fog up easily due to the moisture being exhaled by us humans.

The more modes the A/C runs in, the more moisture is removed from the cab.

Unfortunately, the trade off is fuel economy, and the 3.0L can't really afford to lose any more. This thing sucks gas like top fuel dragster. :-)

 

My 06 and 00 both are dash only, floor only and off for no A/C.