AC only works on MAX a/c

The ac will blow cold but only if I select Max A/C. If I put it on vent but have the a/c on then it blow hot. I don't mean warm I mean HOT like the dial is on hot but it is on Cold ( Blue). Has anyone had this happen to them? What did you do to fix it?

Thanks
D

read the following it may explain your problem

When VENT is selected:

The air inlet duct door, with no vacuum being applied, will block recirculated air and admit outside air. From there, air flows through the system to the instrument panel A/C registers.
The floor/panel door is in the no vacuum position to block airflow to the heater outlet floor duct (18C433).
The panel/defrost door is at full vacuum, closing off airflow to the windshield defroster hose nozzle (18490). There is also some airflow to the A/C side window demisters.
The temperature can be adjusted to heat the air but air cannot be cooled below outside temperature.
The A/C compressor will be disabled when VENT is selected.
The blower motor is on.

also read page 43 in your owners manual the part about Manual Override

FYI the 1999 model is 1st gen

Sorry i havent up dated my info. I sold the 99 an currrently own a 2003 xlt 5.4

A little late with the message, but for future reference:

This problem is usually due to a bad blend door actuator. The Max AC setting bypasses the blend door, and when the actuator is broken, air pressure from the fan can move the door to the max heat position. Sometimes the actuator will just stick in one position, and so adjusting the temp dial will do nothing.

Here is a video outlining the location, removal and installation of the actuator. This guy makes it look easy; getting the actuator in and out is pretty difficult and time-consuming. Also, the actuator post may not be in the right position for getting it installed into the blend door socket.

If this happens, then you will want to reattach the environmental control panel (I removed it from the dash and plugged it in; did not have to hook up the vacuum lines), plug the actuator in, and turn on the vehicle (accessory will work, you don't have to start the engine). Adjusting the temperature control will cause the actuator post to turn to a different position.

I had to do this, and then ended up with the actuator partially inserted, but the blend door was pegged to the cold position and I couldn’t get the actuator placed, so I had to reconnect the cable and reposition the post again so that I could finish installing. It took me forty minutes with an assistant and a pair of chopsticks to get this connector reinstalled, so if you have to move the actuator post, don't disconnect it until you are done, if you can help it.

did you get the problem fixed