Nissan Repair: Altima AC

Question
QUESTION: Hi, AC issue I am hoping you can help guide me.
Vehicle: 2007 Nissan Altima SL, 2.5L sedan.
AC worked fine in the morning, in the afternoon no cold air. I took it in and had the system evac and re-charged (was a bit low) but did not solve the problem. Compressor clutch now does not seem to be engaging. The fuse is good. Can you steer me to help diagnose the problem, relays? clutch? compressor? I am fairly mechanical and have electronics background just limited Air Cond experience.
Compressor is very experience for this vehicle.
Thanks

ANSWER: Hi Elvin,

Question, when they recharged the system, did they replace things like the orifice filter, or check to see if the evaporator or condenser was clogged? Did they do a leak test? Normally this would be standard procedure, but I have to ask.

If the compressor clutch is not engaging then either the connection is bad, or there is not enough pressure in the system to activate it. There is a pressure switch to monitor the high side of the system and if it is not working properly it will not allow the clutch to work. It is a safety device.

Can you check these and get back to me?

Aloha
Calvin

---------- FOLLOW-UP ----------

QUESTION: Thanks for the reply. There was no mention of an orifice filter check, but they did do a leak test and installed dye to verify leaks. They said the system was holding pressure fine but was low (never been touch from new), they did an evacuation and then re-charge with 1.21 lbs.
It was working fine and then just stopped with no warning or gradual warming. When it initially stopped blowing cold the engine would slow and "load" when the AC switch was turned on - like the clutch/compressor was kicking in, but now it does not do that. I was going to try and disconnect the clutch and check for power there, but wanted an expert opinion first to avoid time, frustration or damage.

Answer
Hi Elvin -

You can check for power at the clutch, but that will not diagnose the problem.

My feeling is you should take it back and have them put it on the gauges. If there is blockage the pressure switch will not allow the clutch to work. Have them check the orifice filter as well.

From what you describe, there seems to be poor circulation in the system.

Hope this helps -
aloha
Calvin