I have a 2007 Ford Freestyle and last summer the A/C would only blow cold air when you would accelerate. If you were idling like at a stoplight it would blow warm air. I bought one of those freon refill kits and added freon but it said I was already over pressurized. So now that winter has passed I bought an AC manifold gauge kit and emptied the system and tried starting over. When I add freon the low pressure side goes up way too much and the high pressure side doesnt go up enough. So the low pressure side is over the recommended pressure and the high side is under the recommended pressure. Do I need to replace the compressor or is it something else? (I can also hear the compressor kick in when I put on the A/C)
I hope you took it to a shop and had them reclaim the refrigerant.
When ever refrigerant is removed from a system for service, you must evacuate the system. That means hooking up a vacuum pump to the high and low side and drawing a vacuum to remove moisture.
Any time a system does not operate as designed, the first check is for leaks. If there are no leaks, a part is defective. Usually, the first part to check is the metering valve/orifice. The compressor kicks on and off based on demand, but it will also do so if the system is improperly charged (leak).
If the low side climbs but the high side does not, I don’t understand how that could happen unless there was blockage between the low side and the compressor (Frozen water droplets?), or the compressor may indeed be defective.
Any time you recharge, you should add a small shot of oil as well. They sell it mixed with the refrigerant already.
If you just emptied the system and recharged through a manifold then you just blew air and moisture into the system with it. Those collect in the condenser and prevent proper heat exchange. You must evacuate the atmosphere with a vacuum pump, and you should use a micron gauge to measure and test the vacuum levels.
If you did not do the latter, you should take it to a shop for them to fix. You would spend more money getting the equipment than having it fixed.
You aren’t getting enough airflow over the evaporator. When you stop, no air, no cooling for the AC, warm air out the vents. You move, air flows over the evap, cools the AC, the car blows cool air.
Check to see your electric fan is running at idle with the AC on. You may have 2 fans, one that runs always with the AC, one extra for high engine temps. Also check for a clogged evaporator. They tend to collect debris over the years, back-flush it with a hose.
I agree with Muatangman, except I think he meant the condenser that is in front of the radiator. I had a,similar problem with a Ford Aerostar years ago. It turned out that the fan clutch mounted on the water pump was slipping. It would move enough air through the radiator so that the engine didn’t overheat, but wasn’t moving enough air past the condenser to dispel the heat. The technician noted very high readings on his manifold guage. He directed an air flow through the radiator with his shop fan and the manifold guage readings dropped to normal and the cool air then came out the vents. A blocked condenser so no air flows through it may cause your problem. Personally, I don’t mess with air conditioning systems. I am afraid I might damage more than I fix.
I don’t mess with AC either, but I do know that you would have to pull a vacuum on the system when you are starting with an empty system.
A simple explanation; You have to pull the existing air out, to make room for the refrigerant.
Yosemite
You must also evacuate the moisture. That remains in the system well after the air is “out”. On a system that has already been run, you’ll need to leave the vacuum pump on it for a little while. Inches of Mercury are not enough to measure; must be measured with a micron gauge.
A good gauge is going to be $200+ (the cheaper ones are still over $100 but suffer for accuracy).
Vacuum Pump is going to be $250 - 300 at an auto store for a Robinair or similar. We’re talking a basic pump, not a lot of accessorizing… Used pumps are risky since you don’t know how well maintained they were. I had one… needless to say it was a waste of $$.
The manifold needs to be vacuum rated - O-Ring Seals and not packed valves; they leak under vacuum.
For example, exploded view of a yellow jacket manifold for replacement parts… http://yellowjacket.com/product/brute-ii-manifold-replacement-parts/
When you start considering the cost of doing it properly, you realize you could probably get it checked and even fixed for less. If you don’t do it properly, you’re going to be self servicing it until the cows come home. 
Time to go to the shop. 
Trust me… I’ve done this on various occasions with great success. However, I already have the tools handy. They can be the difference when it comes to improper system operation, but it isn’t worth paying for them if you don’t need them for AC work. One job on the car isn’t justifiable.
Without the tools, you may make your problem worse.