I have a 2000 Nissan Frontier Crew Cab pickup with 52k miles on which the A/C was working fine one afternoon and the next morning it was blowing nothing but ambient temperature air (well, you know the hotter than ambient air Frontier thing - that's a bear during August in South Carolina!). This is a 134A system and it does appear to have considerable pressure on it (I very quickly attached an open R134a charging hose just to see). The compressor and clutch engage fine although it doesn't sound like the compressor is working very hard and the engine doesn't sound like it loads up as before. There's also a whiz/singing noise under the dash when the compressor is on that 'winds up' when the A/C is engaged and 'winds down' when it is disengaged - so I know at least the system is circulating refridgerant a little bit. If I were to guess based on this limited information, it almost sounds like the throttling valve blew out or the compressor is fried (but so suddenly?).
I was a certified A/C tech back when R12 was going out of style and am both an Electrical and Mechanical Engineer so I should be able to tackle this. I was wondering, before I buy a new set of R134a gauges, if someone could supply me the hi/lo side nominal pressures for this vehicle. The manuals in the auto stores don't appear go beyond 1999 and most of the counter folks get cross-eyed when I ask to find a hi/lo spec.
Jake Kohl