A couple weeks back as I was driving my 2006 350z, Suddenly the a/c went from being cold and quite quickly began to blow hot air. ive ran a few tests as follows:

checking pressure of the a/c system low port which was normal

turning on the a/c and checking if the compressor was turning which it did.

the next step that I did was vaccum out the lines and recharge the system but buy no avail, the a/c still was hot.

what should be my next steps to figure this out.

 

Does heat adjust? Door might not be working.

 

it adjusts to heat just fine

 

Heat adjusts just fine.

 

Are the lines cold?

 

Possibly thermal switch.

 

How would I check to make sure that this is the problem.

 

Would I be Touching it by hand?

 

You could use an infrared thermometer..or touch it

 

I cannot give you full instructions for the Z. Never had an issue with it. However, there are a couple of generic related issues. The thermal switch I refer to is the evaporator temp sensor (keeps the evap in the correct zone by stopping or starting "flow" to it if it gets too hot or too cold). This is located near the evaporator, usually held on with a clip. But, beware that there's also a chance of the evaporator being bad either in addition to the sensor or on its own. Finally, there is another sensor in the cabin somewhere (again, never had to look for it) that monitors cabin ambient temp to tell the AC sys when to cycle on/off. Could be as simple as that.

As you can see, it's not quite shooting fish in a barrel, but I'm sure there are vids on YT that can help you out in at least locating the units. As on most cars, the evaporator and sensors are behind the dash. Testing them is another matter. There are usually two conditions, open or closed, which would seem to say you could check them with a VOM. But I doubt its that simple.

I dunno, for areas like this where my own hands-on is limited, I would tend to "take it to a shop", especially for AC, I'd take it to a specialist. I've torn down entire AC systems on my older cars (BMW, Datsun, Volvo, all pretty simple) before but the Z's tight confines and me being an old(er) guy, I'd rather just farm it out. Haha.

 

A/C troubleshooting is a b!tch unless you have high and low side guages. As mentioned above the high side should be cool to the touch. If your A/C runs cold for 5-10 minutes then blows hot you have water vapor icing in the lines. Vacuum it down, replace the dryer and recharge.
Other things to check-
Make sure you're using the correct refrigerant. (R134 IIRC?)
Use a cheap recharge - guage to see if your compressor is producing enough pressure ON THE LOW SIDE.

In the summer a lot of shops offer "free" A/C checks to diagnose problems, that might be a good option. Gl!