Just replaced the ac compressor,dryer,and orifice tube. Vacuumed the system but it won't take 134a.What am I doing wrong?

Did you replace the orifice tube?

Could be a sticking blend door. An ac tech can pit gauges on it and confirm if the charge level is correct and if the compressor is cycling correctly.

You AC compressor is failing, the debris are plugging the tube, replace the compressor receiver dryer and have the system flushed out professionally.

when you replace new compressor/you shoud have to flush ACsystemby usingR11 AND needto replase expantion valve .after that you need to vaccuming AC system.also put AC compessor oil and refill 134A gas.

There's not really a diagram for the actual removal and installation. A good repair manual might list steps like these: First, your system needs to be purged of the freon. Next, unplug the AC clutch/pulley assembly at the front of the compressor. Remove the belt, then the AC lines on the compressor (usually in the back), then unbolt the AC from any mounting bracket(s) and remove. To avoid having to press on and off the clutch/pulley assembly you might want to make sure you're buying a complete compressor assembly. Read and follow those directions concerning oil for the compressor. After installing the new AC, reconnect the lines with new "O" rings. Most if not all compressor manufacturers will not honor any warranty unless you change out your orifice tube (also called an expansion valve) and accumulator (aka the dryer) at the same time. Recharge the system with the appropriate amount and type of freon, most likely R-134a.

Did you replace the dryer,and the orifice tube?If the orifice tube was not replaced,this is most likely the problem,what are the pressures while it is running,and how much freon is in the system?If the system does not have enough freon it it,it will do this,but if it does,the cycling ac compressor is because of the orifice tube,if the system was not flushed out,and there was a new orifice tube installed ,then it is stopped up again.Let me know something so I can help.

any charge port will evac the system
the compressor will not be running
adding oil is not necessary as there is enough in the replacement compressor
run the vacuum pump for a couple of hours and then lock of the system to see it it holds vacuum

You will need to check with a/c gauges, most of the time when a/c line frost is a sign of low on freon.

When the A/C compressor was replaced and recharged, was the system vacuumed and the accumulator and orifice tube (expansion valve) replaced too. Also was the right amount R134a in the system to run properly??
To diagnose problems, an A/C manifold gauge set is needed to read high and low side pressure readings. Avoid adding refrigerant with a simple charging kit like the ones sold at parts stores. Don’t add any stop leak, this can cause problems in the compressor, expansion valve or condenser.

Keep in mind that using an A/C gauge set and seeing BOTH high and low side readings can help in diagnosing the problem when you know what to look for. First, on a 134A system the high and low side service ports are different sizes. AC gauge sets have color coded hoses, the blue color coded hose has a connection that fits on the low side service port and the red hose has a connection that will only fit onto the high side. The yellow hose won’t hook up to anything if just checking the readings; it can be used to connect to a vacuum pump or attached to a refrigerant can or tank.

Normal readings on high and low side with AC OFF (static pressure) - Depends on outside temperature, but normally is between 80-105 PSI Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s - Ranges from 25-35 PSI - Note that on many Chrysler products a normal reading on the low side may be 15-25 PSI Normal high side reading ranges from 200-350 PSI Don’t assume that if adding little Freon is good that adding a lot is better!  Overcharging just a little can decrease the performance of the system and possibly damage the compressor.

With the AC on the coldest setting, use a thermometer in a middle vent. Normal vent temperature readings will vary depending on the (ambient) outside temp. The vent temperature should range from around 42-55 degrees in my experience. If normal gauge readings are obtained and the vent air is cold - STOP don’t overcharge the system. The only proper way to remove refrigerant is with a AC recovery machine so if this is being done at home I can’t emphasize enough not to over charge the system. And actually the best way to insure the proper charge is in a system, is to use an AC machine to recover the R134a and then evacuate and recharge the system with the correct amount. Most cars have the specified amount on a decal under the hood.

Both low and high side readings are lower than normal, this indicates a cars AC system is low on refrigerant and is under-charged. If both low and high side readings are too high, this indicates an overcharged system - too much refrigerant. This also can indicate that the condenser fan is not working, is too slow or the car is overheating and heat is transferring from the radiator to the condenser. 

When the low side goes so low that it’s reading shows it is in a vacuum, the most likely cause is a bad expansion valve or blocked orifice tube. Another possibility is a restricted condenser. Blocked condensers are not as common as they used to be but if a compressor fails and comes apart inside the remnants can end up in the condenser causing it to restrict the flow of refrigerant.

When the compressor clutch is definitely engaged and the low side is high and the high side is low, the most likely cause is that the compressor is failing - it is not pumping sufficiently. Rarely an AC clutch could be slipping but usually this will be accompanied with a squeal or chirp.

I hope this will help you understand why the comprssor failed, Keep me posted, be glad to help you get your A/C running 100% again. 

need to evacuate the system check the orifice tube put back together and re-vacuum system to remove the air from the system.
it's cycling to fast which means air in the system.

any air left in the system will counter any refrigerant in the system.