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Old 05-29-2011, 02:15 AM
BadBrent BadBrent is offline
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Join Date: May 2011
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Default Diagnosing AC problem(s) on 94 XLT 2WD

I'm hoping this is the right section to post this thread in, but if it's not then a moderator may feel free to move it to the appropriate section (my feelings won't be hurt).

1994 Ford Ranger XLT 2WD 2.3L I4, 110k on the odometer

I purchased this truck here about 2-3 years ago, and mechanically the pickup has been just fine, but as long as I have had it I have had to constantly fill the AC system up with R-134a to keep the system running long enough for the compressor not to kick in and out every 5 seconds or so. This summer though, I have not even been able to add freon to the AC system, and have even had a can of Red Dye actually explode in my face and spent 1-2 hours cleaning myself and the Honda Rebel off sitting in the garage.

Several weeks ago I purchased a halogenated gas sniffer (it's a cheapie off of eBay) and I actually managed to figure out where the leak was coming from after all of these years. Right now, my freon is leaking out through the high side service port, and I diagnosed it using the sniffer and the 'soapy water and bubbles' test. I also have a feeling the low side service port valve core should be swapped out too since I have not been able to put any freon into the system. There's still freon in the system because the compressor kicks in and out every 5-10 seconds (at least I'd think there is). When I connect a can of freon though to the system, I know the valve is being opened because the PSI changes from maybe 20 or so with the compressor off up to 45 or so PSI.

I have purchased some average quality manifold gauges and a compressor-powered AC vacuum speficially for R-134A from Amazon, and they should be arriving next week. I have already purchased the new AC valve cores for both the high and low side, and I have a core pulling tool to swap them out easily. Next weekend I plan on evacuating the entire system and hopefully removing all fluids and such, swapping out the two valve cores, putting a vacuum back on the line for a minimum of 1-2 hours, and then filling it back up with the proper ratio of oil and freon.

There are still a few questions I have about this entire process though, but I do know that I want to do it myself rather than have a shop doing it because I've heard reports from friends about some of these companies being extremely shady and severely overcharging (but I'd imagine it's probably people who aren't even qualified to do the work).

If I plug a gauge into the low side, and I can't put freon into the system but I can still measure the PSI while the compressor is on and off, what would cause something like that? I just want to make sure what I'm doing is actually going to fix my problem. I have to replace the high side valve core as it is, so I'm hoping by swapping the low side valve core out as well will fix the problem I have with not being able to introduce more freon into the system.

Is there any chance there could be something wrong with another part of the system? From my understanding, a clogged orifice tube could also be responsible for the symptoms I'm having, and I also understand it could be possibly one of the low or hide side pressure switches (which I think I know where they both are, but a little reaffirmation from somebody who knows would be great). Since I'll have the system evacuated, it would be perfect timing to clean the orifice tube if needed as well as maybe flush the system completely. I 'have' put in a single can of StopLeak in the past, and I know some of that nasty crap can actually clog up the system. Once I learned how bad this stuff was for the AC system, I stopped using it.

As of right now, my plan for next Saturday is to evacuate the line (I know I'm not supposed to vent freon into the air, and I will ONLY do that if I can't get the 'recapture' method to work that I've found on the internet that involves using dry ice to suck the R-134a back into an empty can - I have 3 empty 12 oz. cans with service adapters on them already). I also might possibly have access to a reclaiming machine on the weekend, and that's what I'm hoping for first and foremost. After I evacuate the line, I'll swap both low and high side valve cores out, and possibly just swap out the low and high pressure switches if there's a chance they could be the problem. After I replace the hardware, I'll put a vacuum on the line for at least 1-2 hours and then check the seal on the entire line (pretty sure all R-134a setups need to have 28 inches on the vacuum). After that I'll start with the oil, and I'll put in the correct amount necessary and measure by weighing the can using a postal scale, and then the freon all the way up to 28 oz. I don't even know if I'll have to jump the compressor yet, but I'm hoping the vacuum alone is enough to get the first can of oil and freon into the system.

Another question on my much oil does the system need? I understand you have to have the almost exact right amount of R-134a versus oil for the system to work properly. I'm not going to use premixed cans either to fill the line up...I want to do it properly so I don't have to screw with this mess again.

I know this post is long winded, but I have a lot on my mind as far as this goes and I want to start this repair with as much information as possible. If you've actually read all of this, I do appreciate your time and hopefully there might be something I can do to return the favor in the future. If you need more info from me just let me know. Thank you very much in advance.
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