| A/C Retrofit: R-12 to R-134a |
| If your Jeep Cherokee still has the R-12 freon in its system, and the amount is too low for it to cool you at all--or it's so low that the compressor won't engage--then you might want to try what I did for our Jeep, which is to convert it to R-134a refrigerant (freon). A cheap R-134a refill/retrofit kit ($30 or less) if available at most auto parts stores. I picked up one from my local parts chain here in western North Carolina for $29.88. Why convert to R-134a? Well, if you want to keep your R-12 Jeep "original," then don't convert. But if you value cool air and can't justify the expense of getting R-12 charged every few years--or more often in a leaky system--then read on... I must say, first, that if your Jeep's system leaked out its R-12 low enough to trip the low-pressure cut-out switch, you might have such a major leak in the system that it will require replacement of some part--a rubber hose, the receiver/dryer, evaporator, condensor, compressor, etc., which would result in a very high repair bill. You can check to see if the level is this low by turning on the a/c to either of the three a/c positions (MAX, NORM, or BI-LEV) and, with the engine running, watch to see if the compressor's center part (clutch) is spinning along with the belt and pulley. These systems cycle on and off normally, so if it turns a bit, then stops, your freon level isn't low enough to trip the switch, and your Jeep might be a good candidate for a retrofit providing an acceptable length of time until your next need for a freon charge--which you can do yourself at very low cost. If the clutch is stationary with a/c in one of the three "on" positions, then either the low-pressure cut-out switch is tripped (this keeps compressor from running "dry" and burning itself up) OR there is a problem in the a/c electrical circuits like the a/c dash switches, relays, wires to the compressor, etc. The fittings for R-12 and R-134a are different and are a tell-tale sign (besides a sticker on the a/c compressor) of which refrigerant you have in your Jeep's system. R-12 is possible to get refilled, but is no longer available off the shelf for consumer use in the United States--due to "holes in the ozone layer" and all that jazz... I followed the instructions on the retrofit kit and converted the family's Jeep to R-134a on Saturday, July 5, 2003. It works fairly well, but doesn't get super-cold like R-12 did in this Jeep. A good mechanic told me the reason for this less-than-arctic air in retrofitted R-12 to R-134a vehichles: the condensor, the part of the a/c system in front of the radiator which looks like a small radiator itself, is smaller in R-12 systems than R-134a systems. R-134a condensors have larger tubes and more coils and dissipate the heat from R-134a refrigerant better--which they are designed for--than R-12 condensors, which weren't designed with R-134a in mind. I guess that makes, sense, but I'm no expert. I didn't replace any of the seals in the Jeep's a/c system, or any other a/c parts on the Jeep. I got the a/c system evacuated--a good a/c shop can do this for a small fee and I believe federal regulations require the remnants of your old R-12 to be captured ("recovered" is the term they use) in a "safe" manner. (There was very little left in our Jeep's system due to a slow leak.) After the system was evacuated, I drew a vacuum (with the engine off and cool) using a hand-operated squeeze-type vacuum pump with built-in guage on the suction side of the compressor. I didn't have the correct wrench size for the valve opening bolt, so I used a pair of locking pliers on it for ease and speed. I opened the valve, then attached my vacuum pump on the valve port marked with an "S" on the Jeep's compressor. "S" means "suction" and is also known as the "low pressure" side. The other port is marked "D" for "discharge"; you don't use the "D" port as that is the high-pressure side. Never try to fill the compressor on the D side!!! I "pumped" the vacuum pump until it read 20 inches of mercury vacuum (20" Hg). It took quite a while using a hand pump, I'd recommend using an electric vacuum pump if you want an easier job of it, but my way only took about five minutes' worth of pumping. While still holding the vacuum, you must shut the compressor's valve and then disconnect your vacuum pump. If you forget to shut the valve before removing your vacuum pump, then atmospheric pressure will rush in and air fills up the system, meaning you get to pump it out all over again! If air is in the system, then that's space where freon isn't = less cooling than a properly evacuated system. Then, I simply followed the retrofit kit's instructions, adding on the R-134a-specific fittings over top of BOTH the Jeep compressor's factory ports. You then attach the kit's hose and valve to the first of three included bottles of freon "mix" (see below for explanation of "mix") and the other end of the hose to the "S" side compressor fitting, the new R-134a fitting included in the kit, which is left in place even after the retrofit, by the way. You then start the Jeep, turn on the a/c to "MAX", "NORM," or "BI-LEV" (either one will do) and open the compressor's valve on the "S" side and then open the valve on the freon bottle's hose. My instructions said to turn the bottle upside down. The compressor will not engage at first due to lack of freon in system, until the freon begins to go in and the system's low-pressure cut-out switch is turned back on--the swtich turns on automatically, as freon pressure rises and is not something you manually have to turn on. You must shake the bottle to get all the freon mix out of the bottle and into the system. When the bottle feels cold to the touch and very lightweight, it's empty. Next, shut the compressor's "S" port valve and then remove the freon bottle's hose. Repeat with a second bottle, again inverting and shaking the bottle after it's connected to the compressor "S" port. The Jeep's air seemed cool at this point, but not cold. I opted to put the third bottle of freon mix in the system but didn't invert it to the upside-down position. Ifigured this way, I wouldn't overfill the system. I really need to put a guage on the system--low-pressure/"S" side--and do an accurate measurement, but this will do for now. The kit I used on our Jeep came with the fittings, a retrofit warning label (so mechanics won't try to put R-12 in it), and three cans of freon "mix." The mix includes proportionate amounts of R-134a, polyol ester oil (oil for compressor lubrication), and stop leak additive, all built-in! That way, you don't have to worry about getting the ratio of oil-to-freon wrong. I'm glad the kit has a stop-leak additive. The Jeep had a slow leak somewhere in the system--we had taken it to a mechanic some two or three years ago when he filled it with R-12 (big $$$$$$$) and determined the cause of the leak. The Jeep isn't our daily driver, so we put up with the non-functioning a/c for all these years due to the condition of the Jeep versus the cost of getting the R-12 system up and running again. Why? Well, our Jeep is no spring chicken. It has 213,000 miles on it!!! This seems to work though, as we've used the Jeep's a/c a whole bunch--it's been in the 90's here in Western North Carolina--every day since I did the retrofit, last Saturday. I realize that evaluation at this point is not a long-term trial by any means, but it's a good sign! (Photos of this procedure will be coming soon!) |