Anyone here who can help diagnose a problem with my AC?

I have an 03 1500 Hemi and have a big problem with my AC.

It started 3 weeks ago, when I first started to use the system on hot days here in the UK, which are very rare indeed. The system worked perfectly until then.
I always cycle the AC at least once a week, even in winter, to make sure the refrigerant and lubricant circulate in the AC system.
Anyhow, whats happening is, when the ACsystem has been used and pressurised etc, when you turn the truck off, I can hear a very loud hissing sound, from the front of the truck near to/underneath the air box.
The compressor is cycling as it should and I do get cold air from the outlets. But this hissing sound is VERY worrying?
I wonder if the evaporator in the HVAC is leaking? even though it sounds more like it's from the outside rather than underneath the dash inside the truck.
It sounds like it's near the front passenger wheel well ??????
I'm very worried about the toxic effect withing the cab if this system is leaking.
Any help would be gratefully received.

 

Well y first thought on this is that if you can hear a hissing that loud and its still blowing cold its not a leak. If it was that large of a leak our refrigerant would be long gone by now.

 

Also there is nothing to worry about on the toxic side of the refrigerant. The hissing sound you hear is probably the compressor it self depressurizing or settling and not really a leak. Almost all AC units will have a little bit of a hiss when the unit is shut down. Even your home AC unit should do this. Some just are more insulated and you do not hear it as much. If you got cold AC, I would't worry about it. Like Hanson mentioned, if you had a leak, you would not have AC. Even with the smallest leak, you would run out of refrigerant in like 2-3 days.

 

These are all great suggestions and I thank you very much.
I don't have any AC experience at all and to be honest, it's rather daunting.
Here in the UK as you probably know, we don't often get such high temps to make us use the AC.
I can't remember what It did last year for sure, but It I don't think it made this loud hissing, like a bad/split hose on a radiator.
I know that on one side of the system, I have really hot pipes and on the other side, really cold. So there must be some refrigerant in the system.
I can't see any leaks like fluid/gas coming out........
I'm going for a run out in the truck at highway speeds and will try and see if the AC is cooling properly.
I'll post up about what I find.
Once again, thanks so much for the replys and the helpguys.[sm=icon_cheers.gif]

 

Been out for a run and the AC cools great still. No problems.
Just when I turn the truck off .............Hisssssssssssss LOL

 

makes your truck sound tuff? hehe had a problem with mine on my Avenger I had it was makin hissin noises then one day boom looked like i had NOS with spray release. all though mine had turned out to be a pin hole in the line under the firewall.

 

Mine does the same thing. Asked a tech at rumblebee.org and he said that its normal for our trucks.

 

Hi Al,

From reading through all above, it sounds like your system is essentially running as it should. The one thing I would check is if the condenser fan is in fact working when the a/c is on. That's the smaller coil to the right of the radiator. If it is, its possible that the coil is somewhat plugged. Use a drop cord and shine the light behind it. It should be clean and relatively easy to see through--similar to the radiator. If it is clean-----------------------------------You've become a year older and a little more **** about your truck!!!! :O)!

The high pressure side of your compressor (the hot side) can build considerable pressure--to the tune of 200 psi on a seriously hot day. It carries this pressure through the system all the way to the metering device where it is forced at the given pressure through a tiny little hole. On the back side of the "hole", the compressor is trying to suck it into a vacuum---hence the high hissing noise. If the fan isn't running or the coil that sheds the system heat is plugged in any way, the high pressure I spoke of will be even higher. This can put more stress on the compressor and really lend to sucking up the fuel you pay so dearly for over there.

There you have a very basic ac/r 101 class.

Hope this helps

 

I'm in the HVAC business. The noise you hear is the refrigerant pressures equalizing after shut down. Sometimes it is louder than others. If it is cooling well leave it alone. Next season have a HVAC qualified person give it a good preventative maintenance check up. He will check your pressures. If you have to add refrigerant you have a leak. Refrigerant does not get used up like gas. Hope this helps.

 

As i sit here and ponder this a little more im wondering if your not hearing some condensation dripping off a line and landing on a part of your engine that is really hott. Like when you spill water on a hot burner of the stove. You get that hissing sound.