I know that the A/C is an integral part of the defroster on my '08 Ranger (4.0 Liter) and it is supposed to operate when the defroster is on. Mine continues to 'cycle' off and on when the heat and the defroster are in the 'off' position. Any thoughts as to why?

 

What do you mean by the Heat is in the "Off" position? The temperature has no on/off, just a heat control. If you have the fan control still set to the defroster, it's not off. Off would be in the "Off" position (vertical). Unless the fan control is point to "Off," it's not off.

 

Let me restate what's going on:

When I turn the ***** for the fan to the vertical position and I turn the diverter **** to "OFF" (also vertical) the A/C compressor cycles off and on. (I know, I know there is no actual "OFF" position for the fan - the best that I can do is simply turn it down so that it 'barely' runs but, for all practical purposes, it's as far "OFF" as it can go.) The position of the middle **** - the "TEMPERATURE" **** - can remain in any position - fully in the blue (cold) or fully in the red (hot).

The A/C compressor continues to cycle off and on. Anyone have any idea why or is it simply the way that it's supposed to be?

 

I understand what your saying, i hear mine click on and off all the time even though i have my diverter **** to "OFF". I'm guessing thats just how its made? no expert here though

 

Ok, gottcha. I haven't noticed mine cycling unless I have the right selection switch actually on a setting that would require "defrosting" or A/C. When it's OFF it remains off with no cycling.

 

I don't know about the 08 but my 02 shuts down the A/C compressor when in the 'off', 'floor' or 'dash vent' positions. I think the 08 should be the same. I don't know why the A/C compressor would cycle in the off position. Possibly the A/C clutch relay is stuck closed and is continuing to supply current to the A/C clutch but that does not explain why it cycles on and off.

It is my understanding that the A/C compressor cycles on briefly when it is first started to help keep the system operating when it is not being used. That relay or system may be malfunctioning.

 

I don't know if these trucks have electric a/c controls or if they are vacuum operated. This seems like a control head issue. Luckily for you it's nothing major or expensive. Unlucky for you, it's gonna be a bitch to find. If it is a vacuum control head, there is likely a pinhole leak in one of the vacuum lines. If electric, there is a short somewhere. Whether that short is in the control head or in the wiring somewhere I couldn't tell you. For some reason the system isn't shutting completely off. For a temporary fix you could unplug the low pressure cycle switch, located on the outlet side of the evaporator core, should be between the evap core and the accumulator. The low side port is right by it, should be on the passenger side of the firewall. The accumulator is the big metal can with a/c lines going in and out of it. The heat should still work but you won't have the dehumidifying effect of the air blowing over the evaporator core. The compressor and compressor clutch are good because they are operating, the blower motor and switch is fine, the blend door and thermostat are working fine, it's just the mode selection side that is jacked. For some reason the power to the clutch isnt being cut off. Sorry if my ramblings seem scattered, only half way through my coffee...

 

My 08 did that a couple of years ago. Turned out the freon was low because the condenser had a pinhole leak in it.

 

The compressor cycled on and off even with the switch in the off position? Shouldn't have, the compressor shouldn't do ANYTHING unless the switch is on A/C, Max A/C, or one of the defrost positions. Rapid cycling of the compressor is characteristic of an under or over charged system, but it wouldn't make the compressor cycle all by itself.

 

I made it easy on mine, if this helps at all. I just removed the electrical connector for the AC compressor under the hood. It makes it better for fuel consumption and I don't have to listen to that annoying clicking of the compressor turning on and off continuously