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Discussion Starter #1
Hi all, new to the forum but here goes! I have an 04 Ford Explorer. Late last year the A/C was not getting very cold and now is not getting cold at all. I assumed that it simply needed recharged. However a new problem presented itself before I got the A/C recharged. A few days ago, anytime the A/C / Heater fan is turned on, you can hear a "hissing" sound coming from the rear compartment, driver side. The sound comes and goes and gets loud and quiet with no pattern. If you open the hatch, the sound is coming from the "vent" on the driver side of the rear compartment. Im not sure if the hissing sound and the A/C problem are related or not! Any info would be appreciated.
 

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What engine?
Does it have Automatic Temperature Controls (EATC)?

Some of the AC controls are vacuum operated......it may be a vacuum leak. You need to remove a few panels to get at it.......the front AC should still work though. I think your problem lies elsewhere.
Can you hear or see the compressor coming on?
 

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Discussion Starter #3
4.0L 6 Cylinder. Not to be retarded but Im not sure what an EATC is! The compressor is kicking on and off rapidly, about every 5 seconds or so! The hissing sound only starts when the A/C is on. Im thinking the lack of A/C and the hissing sound are unrelated but unsure. Thanks for the help Jim!
 

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4.0L 6 Cylinder. Not to be retarded but Im not sure what an EATC is! The compressor is kicking on and off rapidly, about every 5 seconds or so! The hissing sound only starts when the A/C is on. Im thinking the lack of A/C and the hissing sound are unrelated but unsure. Thanks for the help Jim!
EATC= Electronic Automatic Temperature Control

Since the compressor is cycling every 5 seconds I'd say it needs some Freon...but you need to find the leak.
The hissing noise could be normal unless it's a vacuum leak....hard to tell from here :)
 

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I'm going to guess on the hissing....
The front is a cycling clutch orifice tube, and will excessively cycle (the compressor) when low on charge.
I think the rear A/C has an expansion valve. I think you are hearing the expansion valve hissing since the pressure is so low.

Bottom line: Get it charged up. Find the leak.
 

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Note: The A/C system is a sealed system. If it needs a charge then it has a leak. Check the A/C connections for a dirty oily grime. If you fing this oily grime it is a mixture of dirt and refrigerant oil and is usually due to a failed "O" ring, or gasket. A charge could last a season, but leaks do not usually get better.
 

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The clutch kicking in and out every 5 seconds is called "short cycling" and indicates that it is low on refrigerant. It should be checked for leaks before recharging and if an oily film is found at the source of the leak, a few ounces of oil should be added to the system after fixing the leak, then evacuation and recharge.
 
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