When I turned on the air conditioning today in my FD, I heard a hissing sound, coming from the passenger side near the glove compartment area, that sounded like air leaking. The a/c did not blow cold, and when I checked under the hood I found that all of my freon had leaked out, as the little glass window that shows the freon status was fogged up. Can anyone please tell me where the freon leak could be?

Thanks in advance for your replies!

 

Pretty much the only way to find this is with a dye. You'll have to go to a place that works with car A/C and have them put dye in your system. You can probably watch them when they run your system and see the leak for yourself.

 

I did get dye put in the a/c system when I refilled the freon last summer, but when I looked for any leaks today near the firewall on the passenger side, I did not see any visible signs of leakage. From hearing the hissing sound, it seems as if the leaking is in a concealed area behind or under the glove compartment on the interior side of the firewall.

 

This is from a fading memory, so it may not be exact:
There are two 1/4" to 1/2" diam hard lines a few inches appart that have an aluminum like finish that go through the firewall from the engine bay, behind the dash into the AC cooling unit (a plastic box with an aluminum ~2 "x 7" x 10" cooling grid, (not to be confused with copper colored ~5/8" heater core lines that pass thru firewall above the center tunnel about a foot to the left.)
These hard lines have nuts that appear to be compression fittings just behind an interior rubber firewall gasket. Sounds like one of the nuts loosened and freon escaped into the engine bay (if the rubber gasket was properly sealing the firewall). You can probably find an exploded view of all the parts in the 1993 Parts Manual in the body section, that you can download from the stickies section at the top of this page. Page 3-H 5 shows the exploded view of the under dash cooling unit. If you can access the nuts from the engine bay side that would definitely be easiest. Hopefully someone who dissassembled or removed theirs can help you furthur.
Hope this helps a little.

 

You cannot assume that [all] the refrigerant has escaped; rather, you need to put refer gauges on it to determine what is going on and perform diagnostics. A low pressure cut out switch will prevent the compressor from operating in the abscence of a charge. The hissing sound you refer to can be cause by the flow of refrigerent through the expansion valve [metering device] located in the evaporator box (as opposed to a leak), however, the system could also be partially clogged at this point.

If the system has had a refrigerant conversion, e.g., R12-->R134, then it could very well be gunked up and clogged. BTW, most leaks in these systems will develop at the o-ring joints or compressor shaft seal.