i have a 2003 3500 laramie quad cab 5.9 and the a/c has a few problems such as low cooling on passenger side , a mist comming from the face vent on drivers side and when i switch the motor off i can hear a hissing noise from under the hood on the passenger side. i have checked the recirculary flap and its still good and working properly. hope someone can help me thanks.

 

You are low on R134a. Get the system re-charged to the proper weight. The hissing sound is the sound being made by the pressure equalizing the high and low side at the orifice tube. That is the high side line on the passenger side.

 

Mine does the same thing, but also has been losing freon. More than likely have a stuck vent door letting outside air in, low freon, and/or a leak. Mine we have not found a leak yet, but am thinking the connection o-rings are bad. Still in the troubleshooting stage in my case, but the condensor has checked out w/o leaks. The mist could also come from the evaporator being clogged.

 

thanks guys for the replys where can i get access to the evaporator to clean it or at least check it

 

Evap is in the dash in a plastic box. Not really going to be able to clean it without removing the dash.

 

i guess ill recharge the system and go from there , thanks for the help

 

If you are really--REALLY-- careful, you may be able to drop the blower motor out from under the housing( three screws , unplug wires, and CAREFULLY pull out from housing so as not to break any vanes on blower wheel), and using a small air hose or similar try to clean the front of the evaporator. I suggest a vacuum to remove as much of the smaller buildup on its face as can be. Spray with a mild soap and water solution and then rinse. Be careful not to overflow the lower section of the housing and allow drainage through the normal drain. In extreme cases, you cannot sufficiently clean the coil without removing the entire case from the truck. Separating the the two halves, pulling the evap and pressure washing the coil from the leaving air side. DO not use a pressure washer at full pressure, the fins are extremely fragile and delicate. There are commercial coil cleaners for evap coils but be sure it is compatible with aluminum and non acid if you do use it.