Posted: Mar 21 2007 at 6:44pm | IP Logged

There are so many points for the referigerant to escape.  It could very well be leaking in the AC pump internally, though usually you get an oil mess.  Plus with so many points that are hard to get a tester to, you'll be scratching your head.

I never found Nissan's truck AC to be all that great anyway. 

Too get the best possible track down.  Take your grill off, and remove your glove box.  This will allow almost unrestricted access to the condensor and evaporator.  Also... are they using a Sniffer, or dye tester?  Sniffers won't detect anything if they're set too low. 

Posted: May 07 2007 at 10:28pm | IP Logged

I've had to replace the Hi pressure hose on my 2003 Frontier twice in the 4 1/2 years I've had it.  Both times, the hose lasted about a year and 9 months or so.  Both times I bought a new hose at the dealer for $100 a pop, evacuated the system and re-charged it with the help of my brother who's an A/C repairman. 

If you've got access to someone with a vacuum pump you might also try pulling a vacuum and see if it will hold it.  If it doesn't you definitely have a leak somewhere.  If not, then it might be something else like a bad compressor, thermo coupler, etc.