Why does my ac pump clutch run when i am in every swithc position except floor and vent. It will turn on and off for all the other positions def, mix, ac, max. Is that normal or do i have a problem. 92 f250 5.8l xlt

 

Normal!!!!

A/C helps defrost to defog the windows...

 

I always unplug mine at the compressor in the winter. Less drag on the engine...

 

Just wondering how that can be. I mean....if is off at the switch then its off at the compressor....right?

 

Somewhere that I don't know of, it gets a signal to activate the AC compressor when you turn on the heater controls. As I said, I disconnect my plug, and my missus's at the comp to not have it come on, in the winter. Mabe in March, I will re-connect it to get it lubed and circulated for the warmer months.

 

Strange thing is, when I want more heat in the cab, I turn the control to Max AC. The compressor isn't turning, but the output is more than the normal heat puts out. I don't complain...I just can't explain...

 

As far as I know in my experiance. Way back it was recomended to operate the ac now and then in the off season to prevent pump seals
lubricated. Then sometime in the 1970s auto mfgs. included a built in
feature of the system to cycle all the time the main control is turned on.
So when you hear the pump comming on and off, thats what it suppose
to do merly just to excercise it. Check out any operators manual from
the 1950-1960s and is written in ink to operate the AC now and then in
the AC off season.

 

As stated above, it helps to keep the compressor and system lubed. It also dehumidifies the air, making the defroster more effective.

 

"Max" A/C just means it recirculates the air from the cab, instead of drawing in fresh air. This works great for heat and A/C... but kills defrost/defog.

 

Air Conditioner/Heater


How The Circuit Works

The Air Conditioner/Heater System contains a Function Selector Switch and Vacuum Valve, a Temperature Control Lever (on the instrument panel), a blower housing assembly, an evaporator assembly and ductwork (behind the instrument panel), and Compressor and Condenser (in the engine compartment).

The Function Selector Switch and Vacuum Valve operate together to control system vacuum and electrical operation. Vacuum motors operate doors to direct air flow. The Function Selector Switch connects power to the Blower Motor and to the A/C Clutch Field Coil circuit.

The A/C Clutch Cycling Pressure Switch cuts off power to the A/C Clutch Field Coil when there is low refrigerant pressure.

The Temperature Control Lever moves a control cable connected to the Temperature Blend Door, which directs air through and around the Heater Core to obtain the desired air temperature.

With the Ignition Switch in RUN and the Function Selector Switch in any position except OFF, voltage is applied to the Blower Motor.

The speed of the Blower Motor is regulated by the Blower Switch and Blower Motor Resistor. With the front Blower Switch in LO, current flows through the Blower Motor and three resistors. In MED-LO, current flows through two resistors. In MED-HI, current flows through one resistor. In HI, current does not flow through any resistors. With the Function Selector Switch in OFF, the Blower Motor does not run.

With the Ignition Switch in RUN and the Function Selector Switch in MAX, NORM (A/C), FLR/DEF or DEFROST, the A/C Clutch Field Coil is activated, and the Compressor starts.

Lever Position and Operation
OFF - Vacuum is applied to the Outside Recirculate Door Vacuum Motor, closing that door to outside air. The Panel Door closes the instrument panel outlets. The Floor-Defrost Door opens the floor outlets. The Blower does not operate and air does not pass through the system.

A/C MAX - The Outside Recirculate Door closes to outside air. The Panel Door sends air to the instrument panel outlets (vacuum on motor). With the Temperature Control Lever in the Cool position, the Temperature Blend Door prevents air flow through the Heater Core.

A/C NORM - Outside air comes through the Outside Recirculate Door. The Panel Door sends air to the instrument panel outlets (vacuum on motor). The Temperature Blend Door controls the air through the Heater Core.

VENT - Air flow is the same as in A/C NORM. The compressor is OFF.

FLOOR - Outside air, controlled by the Temperature Control Lever, is passed through or around the Heater Core. The Panel Door is closed and air is sent to the floor outlets (vacuum at ports A and B of the Floor-Defrost Door Vacuum Motor). The compressor is OFF.

FLR/DEF- The Outside-Recirculate Door lets in outside air (no vacuum at motor). Vacuum is applied at port A of the Floor-Defrost Door. The door moves to mid-position and air is split between the floor and defrost outlets. The Panel Door closes and the A/C compressor operates to dehumidify the air.

DEFROST - With no vacuum at any Vacuum Motor, air passes through the outlets. The compressor operates to dehumidify the air.



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