Where is the exspanion valve on a carrier model 50dk507154

If the compressor wOnt cycle, it means that the pressure is not correct. How much freon, (and what type) did you put in, and did you PULL DOWN (with vacuum) the system to about -29 inches before putting the freon in? Did you use manifold gauges? If so, what is the high pressure, and what is the low pressure, at what ambient temperature?

line that goes to compressor is low side line out of compressor is high side
always fill on low side
also r12 hase been band for sevral years and should not be used
if this freon is r-12 conpatible or replacment then your fine
after leak been repaired and system pressurized and vacumed out
start engine put a/c to max blower motor to hi open windows
conect your fill bottle to low side open valve and system will start filling
when freon reach enougt pressure the compressor should start and draw in
the freon if it fails to start you could jump the low pressure swich to help draw in
freon when system has drawned its capacity shut off your bottle and disconect your line to fill
cap off the valve
if compressor fail to start you have another issus could be electrical
take CAUTION doing repairs to a/c system

Yes it does have a pressure relief valve so u don't blow the line or canister.Hope this helps clear your mind.

the low side is the larger hose that goes back to the compressor.
the high side smaller line comes from the compressor to the to
the condenser ( or the unit in front of the raditor ) on any units
with r-134 from the factory the low side has a different fitting for
putting in freon. some high sides don't use any hose connectors
because there is a site glass in the line where the high side would connect.

Normally due to low freon. Also, notice if the a/c compressor clutch engages, as it will not if the freon is low.

you could have a blockage at the dryer also. have you the ability to put a manafold guage on it to see if the low side pressure is too high which would indicate a blockage somewhere. you should be seeing a number around 30 on the low side with the compressor running. as far as the controls they are vacuum controlled so you may have a vacuum leak making it change. you still should have cold air if ac is on and temp is set for coldest and recirculate is on. hope this helps and good luck

You would need to clean the area around the puncture real well and get some epoxy putty to repair the hole. Allow for the area to dry and harden at least 24 hours.
Then you would need to evacuate the system to make sure no moisture is in the sealed sytem or ice will form in the lines and block the flow of freon. The system will only hold about 1/3rd of a 12 ounce can of R134a which anyone can buy a a automotive arts store. You would need to find a way to tap into the system to charge and vacuum it. The old folks used to purge a system instead of vacuuming it. The newer freon is environmentally safe so no special card is needed to purchase it. However it is still dangerous. You must not breathe the stuff or connect it to the high side of the compressor. The discharge side willl always be the high side and it will always go to the cooling condenser and is small steel line. An ear coming out the compressor is an ideal spot to connect a saddle valve to tap into the system. Before attaching a saddle valve you will fair better if you sand the copper down to prevent leaks. A saddle valve can be purchased at any appliance parts store. Ask for an A-1 line tap. To do the job right you need guages. The low side pressure should not exceed 5 PSI. Thats all the smart pills I have. The gauges will have 3 hoses. Blue(low side)red(high side)yellow(freon). Put your blue hose on the A-1 tap, connect your freon to the yellow hose, and put the red hose on the vacuum pump. Open all the valves on the gauges and turn on the vacuum pump.(Leave the freon closed). After 30 minutes close all valves and shut down vacuum pump. If the vacuum holds, open the freon can and crack open the blue hose, let the freon go in slowly till it equalizes. Bubble test for leaks at the patch. Plug in the ice box and watch the guage drop. The needle on the blue gauge should be close to 5 PSI for a correct charge (over charging will choke down the compressor,not good). Remember the ice box only holds 4 ounces! That is one third of a 12 ounce can. Weigh it in if you want to be exact. Check for leaks. If all goes well it will be good as new.

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whenever the ac system has been opened it should be hooked up to a vacuum pump designed to evacuate the ac system of any foreign debris and oil etc and after should be able to hold a vacuum to show that there are in fact no leaks then if all is ok at this point you can then charge your ac with the proper freon specified for you car when the pressure reaches satisfactory level the ac compressor will then cycle on you should not bypass the low pressure switch

Frost on the low side line means the system is overcharged (too much freon).  Look on the tag insided the fridge and it will tell you how much freon it holds.  Usually 4.25-5.50 ounces on average.  The loud noise sounds like you have air in the system.  I would evacuate, from the high side while running, and let it run empty for 5-10 minutes.  Then while running put the valve core back in the high side.  Then unplug the fridge and charge with proper amount of freon thru the high side.  Wait about 5-10 minutes and plug back in.  Normal low side pressure should be 0-3 psi.  This is a good indicator of the proper amount of freon in a good working system.