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Jeep A/C Repair Made E-ZGet Cool Without Getting Ripped Off From the September, 2010 issue of Jp By Pete Trasborg
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Many shops swear by the thermometer... Many shops swear by the thermometer in the vent when in reality the air temp coming out of the A/C system depends a great deal on the intake air temp. A typical system will only drop the air temp 20 degrees each time the air flows across the evaporator, and you know if your A/C is working well enough to keep you cool without some thermometer telling you. Many on-board-air systems come into existence directly after a guy takes his Jeep to a shop for an estimate on fixing the A/C system. All too often, the shop comes back with a quote of right around $2,000 when the parts total is well under $1,000. Anyone who can fix a brake system or power steering system can fix an A/C system. The reason the shops get away with charging so much is because so many of us don't really understand the automotive (or any) A/C system. It really isn't any more complicated than many of the systems we already understand, we just haven't had it explained to us in the right way. When I scored my new Comanche, as with every other Comanche I'd ever owned, the A/C didn't work. With this truck, it was because the condenser was hammered from an accident. Even I could see that. Like with the other MJs, I went to a few shops and got the $2,000 estimates as expected, so I decided to see if I could fix it myself. A quick Internet search turned up Jeep Air. I sent an email about the shops charging too much, how I wanted to figure it out for myself, and how I needed some tech help. I then got a quick response. I was planning on doing this one outside the magazine; it would keep Cappa and Hazel from razzing me too much and I wasn't sure it was really worth a story, so I didn't include my title, my job, or anything (I was just some guy off the street). The response I got floored me. The guy at Jeep Air responded with things like, "I hate that shops take advantage of the consumers," and "It would literally take under $700 to replace every part in that A/C system," and "I'm actually working on a book that covers this very subject right now." I was further shocked to see that the email was written by the CEO of the company himself, Jon Delucia. This flow chart shows both... This flow chart shows both the high-pressure (red) and low-pressure (blue) sides of the A/C system as well as each component's location. If you are piecing a system together from junkyard parts, you'll need to make sure the parts are in this order or it just won't work. I wasted no time in wasting his time asking all kinds of technical questions, and he batted every one of them back to me with clear and concise answers. I soon came to the realization that A/C wasn't that hard to understand, explained to Jon who I was and what I did, and asked if he wanted to help with a story. He agreed immediately and further decided the only way to really learn was to do it hands-on, so he flew out to Jp magazine's corporate headquarters to share 19 years of A/C repair and diagnosis with all of us. So join us on the other side of the shroud of A/C mystery as we team up with Jeep Air to explain the ins and outs of A/C systems and explain symptoms you might see when parts go bad. Want More?
Jon Delucia is working on a book that goes much more in-depth than we were able to here and it should be available soon after you read this. Also, Jon sent us a huge four-page, single-spaced mini-story in response to some of our questions, which we used in this story. If you want to see the entire four-page answer which gives a bit more background and other information, we've got Jon's story right here on the following pages, starting on Page 2!  The compressor is the heart...  The compressor is the heart of the A/C system, even though its only job is to pump oil and coolant through the system. It sucks refrigerant and oil in on the low side (or suction side), compresses it, and sends it out the high side (or discharge side). Compressors typically die due to a leak in the system. The oil and refrigerant constantly pump through the compressor, and a leak will release both. A compressor should last 150,000 miles, as long as it is well-lubricated. You can check the backlash a compressor has by grabbing the nut on the input shaft and turning it back and forth. Whether you are checking your existing compressor or one you are pulling out of a junkyard, if it has much more play than a new one at a parts store, you might be better off with a newer one.  If your A/C blows cold when...  If your A/C blows cold when you first fire the Jeep up, but after a few minutes blows warm air, your clutch might be shot. If you shut the A/C off for 30 minutes and it then blows cold again, time for a new clutch. Just like the clutch between the engine and manual transmission, this clutch can wear, too. Depending on use, it should last 100,000 miles. However, most clutches die due to too little oil in the system. The resulting heat from the metal-on-metal contact in the compressor overheats the sealed bearing the clutch pulley rides on and fries it. Note the nut (circle) used to check backlash of the compressor.  Jeeps that originally had...  Jeeps that originally had R-12 in them were equipped with a mineral-based oil. However, Jeep Air suggests 6-7 ounces of PAG 46 for all Jeep systems without rear A/C. While the oil is important to keep the compressor lubricated, too much oil can interfere with the refrigerant changing from liquid to gas which is necessary for the A/C to work properly.  Some companies sell a special...  Some companies sell a special oil to "protect" the O-rings upon reassembly. If you slide the O-ring down the male fitting to the shoulder and then assemble it, you should have no problem with cutting the O-rings at all; you'll save another few bucks on stuff you didn't really need to begin with.  The condenser is located in...  The condenser is located in front of the radiator and has become the most crucial part of the system since the switch to R-134A. Its major function is to condense the vapor to a liquid. Since R-12 changes states at a lower pressure than R-134A, the condensers used 40 years ago aren't as efficient as the condensers used today. So if you are piecing together an A/C system, you'd be better off not using anything designed before 1993 (the year the government mandated R-134A). Factory-installed condensers were often painted black for aesthetic reasons, but the paint can decrease efficiency.  Don't force the fittings on...  Don't force the fittings on the A/C system. Many of the fittings are made of aluminum on one side and steel or brass on the other. The quickest way to strip the threads is to force it. If you can get the fitting out of the Jeep, put it in a vice and hit it with a hammer simultaneously on opposing sides. Repeat while working around the hex until it turns easily. By doing this, you loosen the oxidation that forms between the two different metals, and are more likely to get it apart without damage.  Inside the drier is a pipe...  Inside the drier is a pipe that leads to desiccant, similar to that little white package found in a new ring and pinion box or bag of beef jerky. However, this desiccant pack is about 11/4 inches thick and filters out debris in addition to pulling moisture from the system. The liquids pass through the desiccant to the bottom where a tube picks them back up and sends them to the expansion valve. If the drier is beyond its useful life, you might see evidence in the form of the expansion valve freezing or the compressor running too hot (oil and water don't mix). If moisture gets into the system it can react with the R-12 or R-134A and form an acid that will eat the aluminum parts from the inside. For that reason, it is strongly suggested to replace the drier every time you open the system, and to keep it capped until just before you are ready to pull vacuum on the system.  The expansion valve (shown)...  The expansion valve (shown) or orifice tube (used on later systems) is where the liquids change from high pressure to low pressure. It changes the refrigerant to a mist which allows the evaporator to more quickly change it to a vapor, increasing efficiency and decreasing the temperature. If the expansion valve or orifice tube goes bad or becomes clogged, it will appear as an uncommonly low reading on the low side of the system (5lbs or less).  On later systems (TJs, JKs,...  On later systems (TJs, JKs, KJs, etc), the drier and expansion valve are replaced by this unit which houses the accumulator and orifice tube. The accumulator also has desiccant in it, but it can also store a small overage of refrigerant which helps keep excess liquid out of the low side of the system. The orifice tube performs much the same function as the expansion valve; because it has the addition of a screen attached to it much like that found on a fuel pump, it keeps debris from re-entering the system.  The evaporator is where most...  The evaporator is where most of the magic that you can feel takes place. The misted refrigerant from downstream changes state from a liquid to a gas, absorbing heat in the process. That results in the surface of the evaporator being cooler than the surrounding air, and the blower motor then blows that fresh coolness out of the vents. Evaporators typically only go bad from the aforementioned acid due to moisture intrusion, puncture, or from microscopic copper particles that come off the blower motor as it wears, eventually cutting a hole in the aluminum.  An easy way to identify which...  An easy way to identify which refrigerant your Jeep came with is to look for a valve on the fitting at the back of the compressor (top). The older R-12 systems typically came with the compressor already pressurized with refrigerant and oil so the install simply required bolting the compressor in, attaching the lines, and opening the valves to charge the system. The blue cap on the R-12 fitting is a dead giveaway that it was converted to R-134A at some point in the past. The right fitting is from an R-134-only system.  Another trick to get seized...  Another trick to get seized fittings apart is the dual-wrench trick. Of course, we all know about using a wrench to hold one side steady while turning the other side. In this case, the key is to turn the side you want to remove back and forth a little at a time. A 64th of a rotation is all you should expect here, and you will eventually end up with a little pile of oxidized aluminum that will fall out of the fitting. Back-and-forth, back-and-forth, repeat a few hundred times, add lubricant if it is really tight, and it will usually come apart with enough good thread left to reuse-if you were patient enough.  If you are recharging your...  If you are recharging your system, ignore all the gimmicks. If you're A/C system is low on refrigerant but is still blowing cold (say 38-degrees), you will never get a 20-percent improvement over that (or 30.4 degrees out of the vents). Also, much like stops-leak for tires, the leak-stopping solutions are designed to gel up once they hit air and can destroy your compressor, clog the desiccant pack, and clog tubes in the system. Stay away from the gimmicks and use regular old R-134A.  If your tire has a leak, you...  If your tire has a leak, you wouldn't fill it with air that has dye in it; you'd use some soapy water to find the leak. Use the same principle here. Spray the soapy water all along the fittings you can see and most of the time you will find the leak. If you don't, it means the evaporator itself is leaking, and you will need to get a new one.  Once you've replaced whatever...  Once you've replaced whatever components you really needed to replace in the system, you will want to draw a vacuum on it for 20 minutes. This enables you to detect any leaks and draws any remaining moisture out of the system. You should be able to rent one of these in your area from a decent parts store or local shop. If not, this is the one thing that you will have to take the Jeep to a shop for.
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