AC Clutch Not Engaging

[Thafisher]

I am trying to put refrigerant in my 05 Mountaineer and can't do so because the ac clutch isn't engaging.
I have seen it engage in the past, and a few weeks ago I turned on the AC and it blew cold. Actually, for the past half a year the AC seemed to work intermittently.
For example, It'd be hot outside and I'd turn the AC on. It begins to blow cold air after a second then completely at random the air will start getting warm. To resolve this I would typically just press the down button on the thermostat, (Turn the AC lower) even though it was already at it's coldest temp it would usually get cold again after doing that.
Now that I'm finally beginning to use the truck again after it sitting for a month or 2 I noticed I have no AC. It's warm no matter what so I assumed it was low on refrigerant. Which it has done before. (I figured it had a small leak)
But as you know, you can't add refrigerant until the AC clutch engages... The AC clutch won't engage though if it's too low on refrig... So how would I go about adding the refrigerant?
Assuming my AC clutch isn't shot completely that is.

Also, when I push down on the valve high pressurized air comes out. So there's alot of pressure in it, without the clutch engaged of course..

Thanks!

 

[Rcflyer330]

If you have rear ac check the lines that go to the rear. They are located on the passenger side of the vehicle. They tend to rub together and eventually rub a hole. I had that happen and the car would not take refrigerant but the ac pump was still cycling like normal. Start with checking fuses then if you have a dvom (digital volt ohm meter) check the resistance across the clutch coil and spin the center of the pump make sure its not seized.

 

[Thafisher]

If you have rear ac check the lines that go to the rear. They are located on the passenger side of the vehicle. They tend to rub together and eventually rub a hole. I had that happen and the car would not take refrigerant but the ac pump was still cycling like normal. Start with checking fuses then if you have a dvom (digital volt ohm meter) check the resistance across the clutch coil and spin the center of the pump make sure its not seized.

Where would they run? Under the hood, or under the vehicle? I will pull some fuses just to rule that out in an hour.
I have a multimeter, same functionality?
It's not seized, I turned it by hand recently.

 

[Rcflyer330]

Under the vehicle passenger side with mine I could see the oil spot on the frame but not the actual hole. Multimeter/dvom same thing just a longer name.

 

[Thafisher]

Under the vehicle passenger side with mine I could see the oil spot on the frame but not the actual hole. Multimeter/dvom same thing just a longer name.

Ok I will check that out.
How do I go about checking resistance in the ac clutch? I don't have easy access to anything providing power to it.

 

[Rcflyer330]

You would need to pull the connector on the pump and check it there. The reading should be 3 to 5 Ω. That's just to make sure the clutch coil is not burned out. You could also check voltage on the pigtail going to the compressor clutch for 12v.

How's the car been running since the last problems you where having?