2000 F150 4.6, 4x2, 145k

Now and then I notice the A/C compressor is on when I've only got the climate control set to vent (panel or panel/floor, etc -- NOT A/C setting). I notice arctic-cold air, or A/C sounds (whooshing, etc.) after truck has turned off.

Fiddling with climate control switch (panel to Off to Panel/Floor to Off, etc.) seems to let compressor switch off.

Any idea what might be sticking or how I might troubleshoot this so it doesn't run and kill my MPG? Thought of pulling the fuse when I don't need A/C, but sounds like there are other systems on it.

Would it be hard to wire in a kill switch? I'm handy, but don't really know my way around under the hood...
Thanks in advance for any help,
Kirk

 

I think a kill switch can be wired to the lone wire going to the compressor.
But I would look for a new control switch to remain "pure" in my mechanics...
And one needs to know does the compressor switch sense a damper door position indicator?

 

Welcome to FTE severtki! The AC compressor will run in all positions of the function selector switch except off and vent. So with this knowledge, your system is likely to be normal. Good luck!

 

Hmmm... I don't have a vent position. On my 2000 F-150 XLT, the positions for climate control switch are (L-R):
Max A/C, A/C, Panel, Off, Panel/Flr, Floor, Floor/Def, Def.
I would expect compressor to run only on the two A/C and two defrost positions, right?

I was particularly suspicious when I used the heat this morning with the switch on Panel/Floor (it was a bit chilly out), and when I turned off the truck, I heard the A/C noise. Compressor shouldn't have been on for that switch position, and the thermostat should have cut the circuit, too.

So -- climate control switch replacement the most likely? What about this damper door idea?
Thanks!

 

Vent = Panel in your case. Panel/Floor may also be a compressor off mode. The AC compressor runs in these other modes to remove humidity from the air to prevent window fogging that can occur at times. All of this should be covered in the owner's manual for the truck. If you don't have one, you can download a pdf version here. Good luck!

https://www.fleet.ford.com/maintenan...ls/default.asp

 

You're truck is normal, the AC compressor runs in most of the positions even with the heat selector in the hot. This is to remove humidity, to prevent fogged up windows in the winter time.

Oh yeah - The VENTS are on the PANEL.

 

Damper: inside the evaporator/ interior fan housing many vehicles have doors that change position for floor or dash positions, some positions are stricktly heater, or cooling. Like floor-Defrost...
You can look at the original switch first, is it vacuum operated? Or dual? (Ele and Vac) Vacuum switches can hang up, I had an older vehicle another brand from my employer, I had to kick the vent housing to make the damper flip to send air to the dash ...Vacuum systems need a lot of new hose when it starts to crack and leak.
I would stay simple at first, find a replacement control switch from a wrecking yard...

 

What you are referring to is called the blend door in these trucks. He doesn't have a problem, his HVAC system is working correctly.

 

KingRanchMan02,

But what your saying is that Panel or Panel/Floor should be a compressor OFF mode -- and that's exactly when it's running for me. It sure seems like the compressor is running when it shouldn't be -- I'm in modes that just call for air to circulate (vent)...

I'll try to find a used control switch as a first step.

Thanks all!

 

from the 2001 service manual

PANEL/FLOOR
When PANEL/FLOOR is selected:

-The air inlet duct door is at no vacuum, blocking the recirculated air passage and admitting outside air.
--The panel/defrost door is at full vacuum, closing off airflow to the windshield defroster hose nozzle.
--The floor/panel door is in the partial vacuum position, allowing airflow to both the heater outlet floor duct and the instrument panel A/C registers. There is also some airflow to the A/C side window demisters.
--The A/C compressor will be enabled when PANEL/FLOOR is selected.
--The blower motor is on.

FLOOR
When FLOOR is selected:

--The air inlet duct door is in the no vacuum position, blocking recirculated air and admitting outside air.
--The floor/panel door is in the full vacuum position, directing all airflow to the heater outlet floor duct.
--The temperature can be adjusted to mix airflowing through and around the heater core to achieve the desired temperature level.
--The panel/defrost door is in the no vacuum position, blocking air circulation to the instrument panel A/C registers.
--The A/C compressor will be disabled when FLOOR is selected.
--The blower motor is on.

FLOOR/DEFROST
When FLOOR/DEFROST is selected:

--The air inlet duct door is in the no vacuum position blocking recirculated air and admitting outside air.
--The panel/defrost door is in the no vacuum position directing airflow to the windshield defroster hose nozzle.
--The floor/panel door is in the partial vacuum position, allowing airflow to both the windshield defroster hose nozzle and the heater outlet floor duct. There is also some airflow to the A/C side window demisters.
--The A/C compressor will be enabled when FLOOR/DEFROST is selected to dehumidify the air and reduce windshield fogging.
--The blower motor is on.

DEFROST
When DEFROST is selected:

--The air inlet door is in the no vacuum position, admitting outside air.
--Both the panel/defrost door and the floor/panel door are in the no vacuum position so that most of the incoming air is directed to the windshield defroster hose nozzle. There is also airflow to the A/C side window demisters.
--The temperature setting will determine the amount of air that is directed through the heater core and the amount that bypasses the heater core.
--The A/C compressor will be enabled when DEFROST is selected to dehumidify the air and reduce windshield fogging.
--The blower motor is on.

 

steve(ill) why leave out the PANEL position? This Q has come up time & time again. If everything is working right, the AC compressor "will be enabled" in every position except OFF, PANEL, or FLOOR. The AC should run in all the other positions as long as the temp is warm enough. Below the low temp limit the AC shouldn't run in any position.

 

OK, heres the complete run down on the entire system, both manual and EATC.

System Airflow Description — Manual Climate Control

Max A/C
When MAX A/C is selected:

• The air inlet door is at full vacuum, closing off outside air and admitting only recirculated air.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• Blended air temperature is available.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

A/C
When A/C is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• Blended air temperature is available.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

PANEL
When PANEL is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside air temperature.
• The A/C compressor will not operate.
• The blower motor is on.

OFF
When OFF is selected:

• [*]
• [*]
• [*]

PANEL/FLOOR
When PANEL/FLOOR is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at partial vacuum, directing airflow to the floor duct and the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• Blended air temperature is available.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

FLOOR
When FLOOR is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct. A small amount of airflow from the side window demisters will be present.
• The temperature can be adjusted to heat the air, but air cannot be cooled below the outside air temperature.
• The A/C compressor will not operate.
• The blower motor is on.

FLOOR/DEFROST
When FLOOR/DEFROST is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/floor door vacuum control motor is at partial vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct, defrost duct and side window demisters.
• Temperature can be adjusted to heat or cool the air below the outside temperature.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

DEFROST
When DEFROST is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/floor door and the panel/defrost door vacuum control motors are at no vacuum, directing airflow to the defrost duct and side window demisters.
• Temperature can be adjusted to heat or cool the air below the outside temperature.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

System Airflow Description — EATC

AUTO
When AUTO is selected:

• The temperature control setting is manually set to the desired setting.
• The air inlet door vacuum control motor is automatically controlled by the EATC module, based on the temperature setting.
• The mode door vacuum control motors are automatically controlled by the EATC module, based on the temperature setting.
• The A/C compressor is automatically controlled by the EATC module based on the temperature setting. The A/C compressor will not operate if the outside temperature is lower than approximately 6ºC (43ºF).
• The blower motor is on. The blower motor speed is automatically controlled by the EATC module, based on the temperature setting, but can be manually overridden.

OFF
When OFF is selected:

• The air inlet door is at full vacuum, closing off outside air from entering the passenger compartment.
• The panel/floor door and panel/defrost door vacuum control motors are at no vacuum, closing off airflow to the defrost duct, side window demisters, floor duct and instrument panel A/C registers.
• The A/C compressor will not operate.
• The blower motor is off.

MAX A/C
When MAX A/C is selected:

• The air inlet door vacuum control motor is at full vacuum, closing off outside air from entering the passenger compartment.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

PANEL
When PANEL is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside air temperature.
• The A/C compressor will not operate.
• The blower motor is on.

PANEL/FLOOR
When PANEL/FLOOR is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at partial vacuum, directing airflow to the floor duct and the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
• The temperature can be adjusted to heat or cool the air below the outside temperature.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

FLOOR
When FLOOR is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct. A small amount of airflow from the side window demisters will be present.
• The temperature can be adjusted to heat the air, but air cannot be cooled below the outside air temperature.
• The A/C compressor will not operate.
• The blower motor is on.

FLOOR/DEFROST
When FLOOR/DEFROST is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/floor door vacuum control motor is at partial vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct, defrost duct, and side window demisters.
• Temperature can be adjusted to heat or cool the air below the outside temperature.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

DEFROST
When DEFROST is selected:

• The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
• The panel/floor door and the panel/defrost door vacuum control motors are at no vacuum, directing airflow to the defrost duct and side window demisters.
• Temperature can be adjusted to heat or cool the air below the outside temperature.
• The A/C compressor will operate if the outside temperature is above approximately 6ºC (43ºF).
• The blower motor is on.

 

Excellent! Thanks for all the great info.

 

The condensed version:

AC compressor is enabled in all modes except OFF, FLOOR, and VENT (PANEL on some units).

"Enabled" means the operation of the compressor is allowed based on other parameters, it does not mean that it will actually operate.