I am also going through this same problem, my X was taking about 15 mins to start cooling, I had read a post on here that said the compressor is worn and takes a while to come on stroke (variable compressor not switched on and off).

So I buy a new compressor from the states and have a mate do the install and gas. He did this and noticed the Auxiliary fan was not turning, he said this will cause high pressures and heat in the system which is probably why the compressor was on it's way out.

The AC works straight away now but heats up at the lights because the fan isn't running. I had checked quite a few times to see if the fan was going but it never spun.

So I got a new fan from the states, and installed that (petrol fan just changed the motors over as the shroud has a fill in piece where the intercooler is). It still was not spinning, but I noticed today just after starting it it spins but only for about 10 secs, I checked it a few times today and noticed after a drive and re started it itwould spin a high speed but then slow down to a stop.

Don't know if this helps you...

So at the moment I'm looking at the AUC sensor, (little black box connected into the harness). Does anybody know about these??

I also have a this code coming up
41F0 Electric Ventilator - Short Circuit to B+

OK just found this
"That sensor box thing on the top of the fan shroud is for the automatic recirculation"
so that is useless...

When your "mate" installed the compressor and added gas, did he properly evacuate the system, then weigh the freon installed?

I have yet to mess with the A/C on the X, but on one of my other cars, if it does not get fed the precise amount of freon, it will display the same symptoms you are describing. Too much freon, and the system shuts down while in traffic when it's really hot out. As soon as you get moving, it's fine. Nothing to do with the fan....underhood heat raises freon pressure to an unacceptable level, (even if the engine is not hot enough to decide it needs the fan turned on). There is a high pressure switch that shuts the compressor off. Same thing if the pressure is too low. And it is virtually impossible to get this car right with just a set of compound gauges...you must have a scale. You can use a seperate scale, or most of the advanced freon machines have one built in. The older and also less sophisticated machines just use pressure...not good enough.

Yup +1. Good description Skyline

Also if you search. We have members on here that noticed the fan not spin. Then while evacuating the entire system, and filling in freon, the fan kicked on, and increased speed as the pressure reached proper levels.

BTW...this is what my friend's shop uses to refill A/C:

EEAC325B, Service Center, A/C, KOOL KARE™ Plus, R134a

This thing is almost totally automated and computerized. A tech with NO A/C experience could fill a system on the fussiest of cars without screwing it up.

You hook it up, then program in the type of car you just hooked up. It will first completely evacuate the system, and test that it holds a vacuum. Then it tells you to start the car and it will automatically fill the system with exactly the correct amount of freon, (by weight). It adds the correct amount of compressor oil at the same time. It also adds a shot of UV dye, just in case a leak develops. It will pause in between steps and tell you what it wants you to do. Perfect charge every time....pretty awesome. But given the price of this machine, you would expect that.

I have two cars that could care less how much freon they have; charge it until it blows cold, and you're set ('96 Jeep Grand Cherokee and '04 4Runner). My Infiniti is incredibly picky; it takes a good machine to get it working right. Then there's the X5...which has yet to need attention; so I don't know.

Based on what I keep reading on the forums, the X is also very picky. It takes very little freon, and it needs to be pretty close on the money to function properly.

Yes it was done properly, evacuated and weighed. It doesn't matter if the engine is hot or cold, fan must run if AC is on or the pressures will rise and cause boiling of the gas when the car is not moving.
Remember I have an error (electric fan)

hmmmm, hard to know what to do, i still think the gas level needs checking first, then maybe the fan.

why couldnt it be a simple 12v supplied = fan on no 12v fan off, with this pulse thing it makes it all that much harder to fault find, or am i missing something

yeah I have run out of places to look. I was going to put an oscilloscope on the fan today but didn't get time, will have to be next week...

If you have access to GT1, it can turn on fan for testing. Otherwise, you need something applied to that pulse wire. I don't remember what though.