Well I've thrown out the situation of having low freon for discussion earlier and of course consensus is a leak. I added freon by way of one of those guage on the can deals and it seemed to be mostly ok for a while. Today it was around 90 degrees--doggy and I were on a road trip. What started off as a comfortable trip became progressively warmer. I noted the rear air was blowing warm air--not "not as cold air" like what you'd expect from the vents being in the ceiling. Got back home and hooked up my new manifold guages I had ordered which of course, were in metric. Long story short, I added some freon but while the low side pressure seems to be in the proper range, the high side pressure is very low, as in not much higher than the low side. The compressor comes on for approximately 1 second and goes off. Both sides have a pressure drop when it comes on-maybe the low side dips a hair below ideal but I am perplexed-or actually lacking knowledge. I know this is going to be a professional's issue for me, but anyone have any ideas what could be going on. I read a little on the expansion valve but I guess I am wondering if there is anyway to narrow down the problem--guess it comes from always trying to learn stuff.

 

You still have a leak and you're still low on refrigerant.

... at a minimum.

 

Our 2003 Expedition has had issues twice.
The compressor would cycle ON/OFF for 4 sec each.
Our local Frigiking guy has been great and was saying the ON/OFF cycle should be around 30 sec.
First time the condenser had a cracked a tube which he said is common on trucks with large condensers.
After 165k the compressor developed a leak around the case gasket.
He showed me the old parts and how to look for evidence of a leak.
Since there is oil mixed in the freon there were quite visible patterns of dust coated oil below the leaks.

 

My 03 is currently waiting for a custom part from tri valley hose here in town. Problem is similar to yours as my leak is at the connection located right under passenger side where it meets a 10` alum line that feeds the rear. Long story short is Ford does not offer the long part anymore but instead offers a 2 piece replacement, which you have to buy both at 650.00. Hence tri valley hose, unsure of price as yet

 

Just for reference, on time, off time, and total cycle time can vary significantly based on the operating load and the ambient conditions. If you have the factory service manual from 96 or 97, there were graphs in there that showed the typical cycle times. Since the laws of thermodynamics haven't changed and the system design has remained pretty much the same for decades on Fords, the information still is relevant.

 

Would a faulty expansion valve for the rear AC cause the high side pressure to be low? My rear air blows warm, front blows cold--until freon leaks out after a few months. I read a faulty expansion valve can cause the rear air being warm symptom. It just doesn't seem to me that it would effect high side pressure in that manner. Am I wrong??

 

When I had the condenser replaced the next day the rear air was not working and the mechanic said he forgot to check the rear.
They replaced a clogged rear expansion valve and all was good.
The front/rear are parallel, so each has its' own expansion valve.

 

..and a low refrigerant charge will affect the rear system first.

 

Well I suppose it's time to crawl under the X in the dark with the black light. Only place I find dye on the top side is the high and low pressure valves which I suppose is from taking the guages on and off. Most people would have one of your more common leaks/issues but as Creedence said "That ain't me, that ain't me!"

 

I took my sniffer and found a pretty good leak when I took the cap off the high pressure port. I let it breathe a few minutes, put my finger over it for about 10 seconds-when I took my finger off, the alarm went off. There is a small amount from the low pressure port.You can replace those valves like valve stems on a tire so to speak. What are they called??