ac not cooling good unless going down road

presure on low side is low but on high side its exstremely high and it didnt start till i added a little 134a with stop leak in it does anyone have any ideas what i should do

 

What are the pressures?
Leak stop in an AC system is bad juju.

 

That could be part of the problem. In my opinion, all Leak Stops are snake oil. If you have a leak, you need to fix it.

One area that can affect high side pressure is a condenser - especially one that is dirty. They get that way driving down the road. You may need to pull some of the front grill to adequately clean. Put a hose on it with just water coming out of the hose - do not use a high pressure nozzle. Take you time. Go all over it from top to bottom - back and forth - over and over.

Worth a shot.

 

This is a normal condition for (a) cabin is hot, (b) outside temp is hot, (c) no airflow over the condenser. If you spray a little water on the condenser, and the high pressure starts to drop pretty quickly, it sounds normal. There are other things that will cause high pressure. Water in system that freezes as it passes through the Tx valve. That will block the flow of refrigerant and ramp up the high pressure (not to mention greatly reducing cooling until the high pressure switch kicks the compressor off and air flowing through the evap warms it enough to melt the ice. But this cycle will continue until the problem is fixed.

Yesterday my low side was around 35, high side was over 300. Not that unusual for R134a when the outside heat is up in the 90's and there is no air flowing through the condenser except for what the fan can pull.

 

I have to agree with lester - Stop Leak in the AC is a big no no!

Also the " I added a little 134a to the system" is also a big No No! I assume you added via one of those crappy do it yourself kits. You can do more harm than good. An over charged system will not cool better and in fact will cause the opposite less cooling.

Get the leak actually repaired correctly.
Get the system vacuumed and properly charged by a professional.

You will be much happier.

 

And for those complaining about fairly new trucks with poor cooling performance, you need to look no further than the current automatic transmission fluid problems many are reporting. If the factory can't fill the tranny correctly, do you really think they will get the freon charge "spot on?" For 8 dollar's worth of R134a, assuming you have gauges and a decent vacuum pump, you can make certain it is dead on. If it still cools poorly, you will have to check evap and condenser for cleanliness, compressor for proper high/low pressure, and finally the Tx valve which is the heart of the cooling system anyway, it is the device that measures evap temp and sprays freon as needed to keep the temp where it should be.

A good A/C book from one of the parts houses will explain exactly how to test all of this stuff just using the gauges (and pump if evacuation is needed).

 

this guy is spot on take it easy with the hose though, you dont wanna mess up the fins. also might wanna change your cabin air filter that could be cogged and not allowing enough air flow.

 

You can also visit a tool store like Harbor Freight and buy a "comb" made specifically to straighten condenser (and radiator) fins. Mine has like 6 sides with each side having a different spacing. Then you can restore it back to factory condition if you have hit lots of rocks, big bugs and the occasional bird.