So, the AC in my 2010 f150 5.4L is not working. It won't blow cold and it's too hot for that! Now I'm a very green, very newbie back yard mechanic, I'm just learning and trying to be more self sufficient. From what I can tell, it sounds like the AC compressor is not engaging. I did try doing a recharge last weekend but I may not have done it right and just wasted refrigerant. So far, I have checked the fuse and the relay as per the fusebox diagram for that truck. Both appear fine. That's as far as I have gotten as I'm not really knowledgeable enough to know where to move to next. Would the compressor engage if there was low refrigerant? Any help you can provide would be great. Thanks all!

 

Has it ever worked correctly for you? What's the history?

 

I bought the truck used last month and the AC has never really worked. I get some cold air through the vents but it's not AC cold.

So i just poked the Schraeder valve on the low side line with a screw driver to push the pin in and there was no release of gas? Could it just not have enough freon in it to engage the compressor? Should i just put a recharge kit in?

 

I don't know much about AC systems but I do know that if all of the refrigerant gas has leaked out then moisture and other gases might have leaked in. You need to have the system checked for leaks (there's a reason the refrigerant is gone), maybe a few components checked and changed (there's a drying unit for example, plus seals might be bad), purged (vacuum to remove all gases), then properly refilled.

Parts like this, below, have desiccant that gets saturated. Just one thing that needs to be verified. Once AC systems leak completely out of refrigerant all kinds of problems can crop up.

https://fjcinc.com/what-is-the-diffe...n-accumulator/

 

AC tech here. if there was no gas when you poked the schrader then it has leaked out. nathan is correct. there are band-aids like the cans of r1234 refrigerant you can get at a part store but if the system has been open to the atmosphere it won't work great until you fix it properly. you may not do all of this but I figure the procedure may help someone else out.

the components are likely still good, they have safety cutouts that would keep the compressor from engaging at low pressure (and high pressure but that isn't your problem). you can tell if the compressor is engaging by looking at the front plate of the pulley, if the whole thing in spinning, it is engaged. the pully should always spin but the plate will be stationary if power wire to the clutch isn't hot (not engaged).

the process to fix it would go a little something like;

hook up refrigeration gauges verify no pressure

charge the system with nitrogen (because it won't add moisture, but if you are doing this in a garage and the system has been open you probably won't hurt it), use the nitrogen charge to look for leaks. I start at about 175 psi, take some dawn dish soap mixed about 1 to 4 or 5 with water and spray down every joint in that ac system. if there is a leak, you will see bubbles, they can take a few minutes to show up. hopefully it will be obvious and easy, if you dont see a leak, work the pressure up in increments of 25psi. or so, i wouldn't recommend going much past 300 psi total.

once you find the leak, repair it. leaks can show up in evaporator coils (inside of cab), condenser coils (stacked on the radiator), the compressor shaft seal (between the compressor body and the pully) or any hose/ pipe connection. often times it is a rubbed line and that the easiest to deal with. if you get lucky and have a quiet garage, hearing the leak is sometimes the best way to find it.

once the leak is fixed, change the drier (which is attached inline somewhere between the condenser and compressor and about the size of a 22oz beercan, not sure on a ford actually)

leak check with nitrogen again to make sure you have a closed system

system back together, you will need to vacuum the pressure down to -30 (technically 28 but whatever) this will boil off any moisture in the system and prep it for charge. let it stay on vac for a good 30-45 minutes if the system has been opened for awhile or you used regular air instead of nitrogen. shaft seal leaks will commonly show themselves under vacuum as well so if your pressure creeps back up then that may be an addition issue.

at that point you would be ready to charge but I am getting into the weeds and didn't mean to make a class of this. hopefully knowing what needs to be done will keep you from getting taken advantage of if you take it to the wrong shop.