Today I noticed air conditioned air blowing out of the panel vents when I put the temp adjustment to cold even though the selector was in panel and not in AC position. What might be causing this.

Thanks, John

 

A vacuum leak. Look for small hard plastic line behind the battery. If you find a rupture in ANY vacuum line, buy some rubber line that will barely slip over it, cut out the bad section, & replace it with the rubber.

 

PANEL is your vent position. If the outside temp was cold, sounds normal. Also, if the previous position was in a switch setting that runs the A/C compressor, you're just getting the last of the cooled air from the system.

Open your hood and look at the compressor clutch to see if it is erroniously operating while in vent mode.

You don't have a vacuum problem. Vacuum is used only to select inlet and outlet flow and has nothing to do with the operation of either temperature control or compressor operation.

Steve

 

I noticed my 1999 f250 light duty has the same symptom. no matter what position the dial is set to ac, panel, floor, defrost etc. the air coming out is very cold. when the temp dial is on cold. do i have to set the temp to warm or is there a way to keep the ac from coming on? i think it is having some negative effect on fuel economy.

 

Compressor operates in in all positions except OFF, FLOOR, and PANEL (VENT).

Safety and comfort were more important to the designers than fuel economy at the time of the design.

Steve