Iíve owned two JGCís (í94 and í00) and really liked both of them, but each has had a virtually identical problem with leaking A/C evaporators that has driven me absolutely crazy. Although I have found much information regarding leaking A/C units and wet floorboards in previous forum posts, service bulletins, and other websites, none of it has been very applicable to my personal experience with these leaks. Surely others have shared this problem, so I thought Iíd post details here.
The most common fix cited for wet floor boards is to clear an obstruction in the drain tube by drilling a small hole in the center of the circular condenser duct and use a wire or other object to clear the obstruction. There is an explanation, service bulletin info, and some good photos of the evaporator shape and design at: http://www.aircondition.com/tech/questions/4/
However, neither of my leak problems had anything at all to do with an obstruction in the drain tube, so this was a waste of time. The issue is particularly difficult with ZJ models, because on these the drain tube is designed to flow into the frame and the discharge side is not reachable. On the WJ model, the discharge side of the drain tube is clearly visible and reachable from within the engine compartment, so technically you could attempt the ďclear the obstruction in the tubeĒ problem without having to drill the hole in the duct.
Another suggestion Iíve read is to examine and reapply sealant where the drain tube enters the frame. The idea here is that condensate water fails to drip from the discharge end of the tube, and instead flows along the underside and back into the vehicle. Once again, this had nothing to do with my problem. On my WJ with the visible discharge tube there was clearly no water coming from it whatsoever Ė it was all leaking into the vehicle. Iím certain the same was occurring on the ZJ but I could not verify it at the time because the tube was not visible.
The bottom line is that both of my leaks were caused by a structural failure and design defect in the shape, material, and function of the circular condenser duct and drain. The problem occurred from the plastic on the backside of the duct somehow becoming compromised and a forming a small hole, allowing water to leak directly onto the floor instead of out the drain. The maddening part is that because the hole forms on the backside against the frame it is not really visible until you actually remove the evaporator (huge job) or cut out the duct. More on that laterÖ
I have a theory on how this hole might form. Because the circular duct is designed with the drain tube in the middle of the circle and not the bottom, by definition the condensate water has to collect and lay in the bottom half of the circular duct before it can build enough to being flowing out the drain. This is part of the design defect. Bear in mind, I live in central Florida so Iím running the A/C a good 5-6 months straight. Over time, with that water constantly laying in the bottom of the duct some type of acidic reaction or other event occurs that causes the plastic on the backside to weaken and eventually form a small hole. Because it is on the backside you canít really tell where it is coming from, but now all your condensate water ends up running down onto the floorboard and making a huge mess.
So, once this occurs how do you fix it short of pulling the dash and replacing the whole evaporator? On my ZJ, out of sheer frustration I ended up literally cutting the entire circular duct off of the evaporator, and rigging a small funnel and tube to collect the water and send it out the drain hole. It worked, but it wasnít pretty. I also wasnít careful enough back then to examine the part I cut off, I just threw it away and rigged the funnel and moved on.
When the identical problem started occurring this year on my 2000 WJ, I set about to take it more slowly. Took a Dremel cutting tool and a chisel and began cutting away only the 1/3 or so portion of the circular duct that is BELOW the bottom of the drain tube. It didnít take long before I located the aforementioned hole on the backside that was causing the problem. To fix it, I made use of epoxy putty you can purchase at any hardware store. After cutting away the bottom portion of the circular drain I used the epoxy to form a new bottom, so that now when water flows downward out of the evaporator instead of collecting and laying in the bottom of the circular duct it flows directly out the drain tube. The interior cavity of the drain duct is not hollow, it contains vertical splines that provide structure for the epoxy to adhere to. Also keep in mind when working with epoxy putty you need to moisten it a bit before applying to ensure it makes a good, waterproof ďstickĒ. If you apply it dry it tends to not stick well enough and youíll continue to get leakage.
So, thatís what Iíve learned from many, many hours of frustration dealing with maddening JGC A/C condenser leaks. I hope this information helps others who experience the same.