AC Seems dead

Hi all
I own a UK '97 Prelude 2.2 VTi which seems to have a fault with the AC.
The green light illuminates but there is no nice cold air or a dip in the
revs. Is there anything that I can check or is it a visit to a AC technican?
I've just purchased the car and was told the AC has a re-gas 2 years ago.
Many thanks
Jules
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If your system has any residual pressure (momentarily poke the H pressure valve near the (front) condensor pipe, you may get away with a simple recharge with some Duracool. Most garages can do this for about $20-30.
Otherwise, go see an A/C shop and get quote. All A/C systems leak a small amount of gas (mostly out the compressor shaft seals) over time. The other most common leak is the hose O-rings, followed by corrosion holes.
If your system has no or minimal residual pressure, then there's air in the system which has to be removed. You cannot simply recharge an unevacuated system and expect it to work, because it won't.
You should know that A/C shops are licenced and have to comply with a whole raft of regulations.
The A/C shop will do the following:
a) replace the hose O-rings. They may want to replace the drier canister. Resist this suggestion unless they can demonstrate that the drier is defective. Just because its 9 years old is not adequate justification. When the hoses are removed to replace the O-rings, the drier connections have to be blocked to prevent contamination with atmospheric moisture. A couple of minutes of exposure won't hurt it.
b) pressurize the system with nitrogen to test for leaks. Compressed air cannot be used because this causes rapid oxidation of the compressor oil into damaging (and corrosive) compounds. If there are leaks, they will inject some dye and small amount of refrigerant and try to locate them. If found, the injected refrigerant has to be recovered, not vented.
c) Assuming there's no leaks, evacuate the system and test that the vacuum is maintained.
d) Assuming a maintained vacuum, recharge the system with (now getting expensive) R143a refrigerant. You may want to check out the Duracool web site for alternatives.
e) charge you about $300 for the above, plus any parts. Hose assemblies are usually outrageously expensive. You may want to search locally for a shop that can rebuild hoses. This generally takes some effort on your part, as most shops prefer to use OEM parts. What is often required is that barbed pipe ends have to be gas brazed on to the existing pipes, and new hoses crimpted on. Rebuilt hoses typically cost about 1/2 or less than the OEM.
Stewart DIBBS
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Thanks Stewart.
I took it to a local auto electrician who pumped a small amount of gas into the cannister and the AC works immediately. They then refilled and included a dye as you mention above. I was told to return if it stops working again so they can trace the leak.
I've noticed since the re-gas that every so often, with the AC on, you hear a hissing sound from the front vents. It lasts around 5 seconds or so.
Thanks for the advice.
Regards
Ju
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