gday all - having a bit of trouble with my air con in my 98 XR6 ute at the moment, turned it on today and it started making a loud sort of hissing sound from near the glove box, with only semi-cool air coming out from the outlets. Had a look at home and it looks like all my hoses are connected firmly from under the bonnet, as well as under the car. I took out my glove box and had a look there too - all seemed fine and in place, however the hissing noise is still there with no cool air when the air con is on. Im assuming I have a vacuum leak somewhere - but what Im not sure on is - would it hiss if there is little or no gas left in the unit, bearing in mind that the unit would no longer be gas compressed - resulting in a possible hiss of remaining escaping gas. I think it may be coming from the solenoid but I couldnt really pinpoint where it was coming from.
Im hoping that I only have to regas my aircon to fix the problem, but Im thinking that Ive got a vacuum leak somewhere else...
Any help would be appreciated.

yeah, the vacuum connections are made behind teh glove box (CC and aircon) and if you just have aircon behind teh control unit too.

Check those for hissing.

Does the hissing go away when the engine is under load. If it goes away it's def a vacuum leak, if it remains, it's not vacuum.

thanks for that - will put the foot down a bit tomorrow and see if it remains cheers.

No leaks at all?

You can check your A/C by running it for about 5 - 10 mins max cool, high fan(1st engine start is good as the radiator hasn't heated up), visibly check the compressor clutch is engaged, and with the black plastic surround removed (the one that sits around the hood catch)have a feel of the condensor (sits in front of the radiator), it should feel warm/hot pretty much over the whole surface area - if it only feels warm maybe the top half or less, then that's a good indicator that there's been a loss of refrigerant. If you have a look at the sightglass on the receiver/dryer (cylinder like item sitting nearby), if there's a fair amount of bubbles flowing through, that's a good indicator for loss as well.
A system running properly should be pretty hot on the compressor output pipe to the condensor, condensor should be hot pretty much over it's whole surface, the pipes to the evaporator at the firewall should feel pretty cold.
It's a rough test, but should give you an idea in case the heater box doors are playing silly buggers. If you do have a refrigerant loss, obviously there may be a leak, so it may add to the recharge cost.

As mentioned though I'd suspect a hose leak - but check your A/C as above.
If you have to pull the dash to play with the airbox - consider a CC conversion - I'm doing mine at the moment - XH's need a bit more modification than the E series though .

thanks for that, will advise on end result.

mine made the same sounds as yours, it was a blocked TX valve

the quickest easiest test is to hold your hand on the suction hose near the firewall. its the larger one of the two hoses. if its not real cold your down on gas, thats given your compressor cuts in in the first place.