2007 F-150 - 4.6L - 99,000 miles - Std manual temperature control.
Late last summer, I noticed that my A/C took a while to to get cold and never got real cold. With the weather finally getting hot, I noticed the same problem.
I borrowed a friend's gauges to properly recharge my system. When I initially hooked up the gauges, the low side was about 10 psi low & the high side was about 20 psi low. According to the chart, this indicated a low charge.
Once I connected the can of freon (134a), i opened the valve on the can the slowly opened the valve on the gauge manifold. The low side gauge immediately shot up to about 100 psi. Now, the low side stays high. According to the chart, high psi on the low side & low psi on the high side with a vibrating needle indicates a faulty reed valve on the compressor. However, the needle on the gauges are rock steady.
How the A/C inside acts has not changed.
Does anybody have an idea of what is going on? Am i looking at rebuilding the pump?
Any help is GREATLY appreciated!!!!!!!

 

Did you open the valve with the engine and compressor running? Was the can right side up?

 

If the low and high sides are now the same pressure, it means the compressor isn't running.

 

Like they said, the engine has to be running with the compressor operating to fully charge the system. There may be risk of exploding the can by hooking it up with the compressor off. If the low side pressure went to 100, the compressor couldn't have been running. What are the pressures exactly with the compressor running? I always set the refrigerant can in a pot of hot water so it will evaporate quicker.

 

THANX for the replies!!!!
The engine was running. I could hear & see the compressor kicking in but was not running consistently. It wold kick on, run for a short time, then kick off for a second or 2. The controls were set to Max A/C, Full Cold, & the fan on high.
The pressure would not drop on the low side when the compressor would kick off. The pressure would stay steady.
The high side would run about 190 when the compressor was running and about 150 when it was not.
Here is a picture of the gauges when the compressor was not running. I had a hard time getting the picture.


This picture is with the valves on the gauge manifold closed so it was reading the pressures off the system not the can.

The can was upright and was not sweating or getting cold when I tried opening the valve on the can.

I am wondering if 1 of the valves in the compressor is sticking not allowing the low side pressure to fully drop?

 

I'd suspect a leaky manifold in your gauge set. Disconnect the high side connection from the high pressure line to see what happens. If the manifold is leaking across from the low side, you'll know it immediately.

 

I think you may have overcharged the system

 

ProjectSHO89: THANX! I will try t check that tonight.

Patman: I will check that after I check what "Project" suggested.

ALL: I talked to an HVAC guy with one of the heating and air contractors I work with a lot. He seams to think I am getting some bleed-by. He said usually you blow past an o-ring before damaging a valve. (From when I opened the valve on the can too fast.)
Now, I think what I need is an accurate schematic of the A/C system for this truck so I can know where to check.
I don't want to pump down the system until I know what too look for & where to look.
Someone else suggest the orifice tube as it work like a valve in this system. Does anybody know if this is correct?

THANX AGAIN FOR EVERYBODY'S HELP
BassnKY

 

The orifice tube could be partially plugged. The orifice is a fixed size. In the old days the orifice was a variable opening valve but no longer. If the orifice is plugged, you need to change out the reservoir/dryer too, because that is where the dessicant came from that plugged the orifice.
If the suction pressure really is 100 psig, it definitely won't accept any more refrigerant from the can.
Try a different set of gauges and see if it is the gauge set.

 

Seriously, CHECK YOUR MANIFOLD FIRST. If it isn't working properly, anything else you do is a waste of time.

Make sure BOTH valves are fully closed when measuring pressures. If you are charging, open ONLY the low side valve.

 

UPDATE:
I hooked up the gauges and did not open the connection valve (Both lines have a valve on the quick connect also) on the high side. The low side pressure read 30 psi. I believe the gauges are leaking, not working correctly, or both.
When I tried to put freon in, the pressure on BOTH sides went to 60 psi (I think my can is running out) and stayed there.
I think I am going to try a different set of gauges and see how they act. If the gauges are reading correctly (Taking the leaking aside), it sounds like the I have a valve problem.
Any thoughts?

 

OK, I went to AutoZone and used their gauges. The ambient temperature was 80 degrees. with the compressor not engaged the pressures read 25 psi L & 150 psi H. When the compressor kicked in, the low side would go up to 50 psi & the high side would drop to about 110 psi.
Any thoughts?

 

That's strange. With the compressor not engaged I think the pressures should be equal?

Just guessing, it sounds like you have a blockage in there somewhere.

 

The pressures ARE supposed to be the same when the system is not operating. If the gauges read anything else and, assuming the system has not been operating, then the gauges are defective.

You should only see a differential in pressures when the compressor is operating. It should pull the low side down and push the high side higher.

Static pressure in the system should be approximately ambient temperature in degrees F multiplied by about 1.2 for summertime US temps. Close enough to see if there is any charge in the system.

 

With all this in mind, I think it's time to take it to a pro. If the gauges are good, you definitely have a problem.