A/C Blowing Hot Air and Releasing Pressure

[bbrown0414]

I had a leak and just replaced the A/C line on my 94 Explorer Sport. The A/C was blowing hot air and I assumed it was just due to no R134 in the system. I charged the system and could only get it to 25psi. When I let it run for a second, the pressure release valve on the back of the compressor blew out a burst of R134. The air never got cold before it blew out. What could be causing this.

 

[FL.Cracker]

I had a leak and just replaced the A/C line on my 94 Explorer Sport. The A/C was blowing hot air and I assumed it was just due to no R134 in the system. I charged the system and could only get it to 25psi. When I let it run for a second, the pressure release valve on the back of the compressor blew out a burst of R134. The air never got cold before it blew out. What could be causing this.

Did you evacuate the system properly?

 

[bbrown0414]

Yes, every thing was done correctly. Also, I don't know if it makes a difference, but when it blew out, it was like a greyish color almost like grease mixed in.

 

[FL.Cracker]

Yes, every thing was done correctly. Also, I don't know if it makes a difference, but when it blew out, it was like a greyish color almost like grease mixed in.

Blew out greyish from the pressure release valve or the vents in the cabin? Does the system hold pressure anymore? Has the evaporator core ever been replaced, they are prone to cracking where the top line enters the core.

 

[bbrown0414]

It holds pressure, but only around 15 psi. I just replaced the evap. due to it leaking there. As far as I can tell, it is holding steady at 15 psi so there shouldn't be any leaks.

 

[FL.Cracker]

When your filling it do you have the two wires going to the pressure switch (on top of the accumulator) jumped so the compressor clutch is always engaged?

 

[bbrown0414]

No, no wires are jumped, but the clutch seems to stay engaged.

 

[1Byounkin]

I'm having the same thing with my a/c. Stuff blow out the compresser. It had the dye in it, but could not find the leak.

 

[bbrown0414]

Yeah, I had the dye in it, but when it blows out the back, it covers everything! I just happened to be watching when it blew out!

 

[1Byounkin]

It did this last year. Haven't checked this year yet. Everything has been replaced, but a few things. The truck was idling and pressure released.?? Checked the pressure and looked good. The truck ran and air got cold. But if the engine is rev to 2000 to 3000rpms (normal driving), than the compressor would kick off and on > which would not make much cold air. This is the mystery I'm at now. Mine is also at R 134.

 

[cloaked_chaos]

I had the same problem with one of my explorers. The cooling system had been empty for quite some time due to a bad compressor and leak in the line so I replaced the line, compressor and accumulator. I was able to put enough r134a in to get it cooling, but whenever I would get over 3,000 rpm it would shoot out of the valve on the line coming out of the compressor that dumps it when the pressure is too high.

It turns out my orifice tube was clogged with crap, and was not letting the r134a pass by at a very quick rate, causing the pressure buildup and subsequent discharge.

I'm not sure exactly where the crap that was clogging it came from, but after I replaced the orifice tube (only $1.99 at autozone) the cooling system worked perfectly from then on.

 

[bbrown0414]

I think I am going to try that! Do you happen to know of a good write up on replacing it?

 

[cloaked_chaos]

Here is a diagram showing where the orifice tube is located.

The orifice tube is in approximately the center of the image. It is located inside the lower pipe of the a/c evaporator. Basically just remove all r134a from the system, pull the connection apart at that joint with the special a/c hose removal tool and use thin needle nose pliers to pull the old orifice tube out. Make sure you don't break it apart as they can be extremely brittle after years of sitting in there. You may need to lubricate it to get it out. I don't know which lubricants are compatible with r134a so I would just squirt a little PAG 150 oil in there. PAG 150 is the standard lubricant for the a/c system anyway, and you can get a 3oz bottle of it at autozone for $6.99.

Once you get the old orifice tube out, lubricate the new one with the PAG 150 oil, and push it back into place approximately in the same position the old one was in. Using the new o-rings that the orifice tube should come with, re-install the a/c hose and then go through the steps of vaccuuming the air out, testing for leaks, and refilling with new r134a.


Autozone has kits for special order to help you remove the old orifice tube but I found that a little lubricant and some needle nose pliers worked just fine. I was too rough when i was pushing the new one in and I broke it (it can be a really tight fit), so I just went to the store and bought another one since they are only two bucks.

I take no responsibility if you follow my advice, and I don't guarantee that it is the proper way of doing it, but this is how I did it and it worked fine for me. This does not cover flushing the system to clean out the rest of the crap in the lines (which I highly recommend) since I replaced everything except for the condenser and evaporator.

 

[bbrown0414]

Thanks for the diagram! It will be a few days before I can try this. I am going to go look at a 1998 and 2004 explorer on Mon. or Tues. and I may buy one of those! Either way, I will still be trying to fix this one, it may just be longer before I try it if I buy one of the others. I will try to give an update whether it worked or not when I try it.

 

[Iron Weasel]

The diagram is accurate, however, it doesn't convey the fact that orifice tube is located in the end of the evaporator that sits underneath the accumulator so you'll have to remove the accumulator to be able to get two wrenches onto the ends of the liquid line and the evaporator. It's easier if you disconnect the accumulator from the upper evaporator line and leave it hooked up to the A/C line so you can just swing it out of the way.

Also, the stock R-134a system calls for PAG-46 oil, not 150. 150 is a fair amount thicker than 46.

 

[bbrown0414]

I figured I would give everyone the update on this. It was the orifice tube that had clogged up. Thanks for telling me about that cloaked_chaos, I would have never figured that out! It still doesn't blow as cold as it should but at least its cool air now and I can drive it with the windows up! If anyone knows of something to check that could make it colder, please let me know.