High pressure on the low side

[silverbullet99]

Tonight I helped a friend put in a new condenser and a new orifice tube.

Put in the new parts (w/ oil in them), put everything back together, and evacuated the system (less than 30hg).

I put the first can in as a liquid on the high side, it went right in. Started the second can and it went near half.

Started the truck and put gas on the low side. The low side was reading about 75 and the high side was cycling from 60 - 100(compressor off/on) Started the next can and the low side went up to 120 and the high side was now at 125 - 175 (compressor off/on). I believe I saw the high side go up as high as 225.

The outside temperature is hovering about 73deg tonight and the A/C felt somewhat cooler than that.

The high pressure on the low side has me thinking that there is a problem here, maybe a clog.

The old orifice tube looked great, could have reused it.

Any ideas on what I did wrong or what is going on with this A/C? What should I check?

Thanks for any help,

Jim

 

[rayamx69]

I would first check the orifice tube to make sure it is the right one and that it is in the right way. Did you flush out the system before you recharged (evaperator, lines etc). Also were the pressures fine before you started?

 

[silverbullet99]

Pressures were fine to start. I made sure I put the orifice tube in the way it came out. Didn't compare to the new tube.

Will have to pull the tube and flush the system. Any easy way to do this?

 

[rayamx69]

the easiest way to flush the system i sto disconnect the lines and pour ac flush through them and blow it all out with an air hose. the only reason the low side is going to be that high is an obstruction some where. W hat are the high low pressures at idle and at about 2500 rpm?

 

[Maniak]

I've had 2 orifice tubes "blow in" over the years.. I get a can or 2 in the system and then the low and high pressures end up about the same.

After the last one I used a set of channel locks (the kind with jaws that look like pliers, not the flat ones) and I crimped the tube where the orifice when in all the way around a little.. now the orifice tube won't blow in (and didnt)..

You'll know if blew in when you go looking for it.. and its not where it was when you installed it.

Your "supposed" to change out the evaporator when that happens.. I didn't both times it happend (different evaporators each time).. and my a/c still blows in the low upper 30 to low 40 range.

~Mark

 

[rayamx69]

also here are the specs on your system
oil capacity 8 oz
ref capacity 32 oz
Low pressure should be 30-50 at idle
high pressure should be 150-225 since you have a new condenser

 

[rayamx69]

maniak is correct. a busted orifice will wreak havock on an evapporator. its like a radiator, and if it gets clogged the pressure will skyrocket

 

[silverbullet99]

I don't exactly remember the pressures at higher rpms. Will check them next.

Thanks for the help, I'll let you know what I find. Also when I blow out the system where do I inject air and where does it come out. Then I would put in the full amount of oil where would I put this much oil?

Thanks!

 

[rayamx69]

blow air through which ever port you put the flush in. i would put the flush in the line that goes to the top of the evaperator, and blow air through it so it comes out the bottom. and clean the rest of the lines individually so you dont contaminate the new condenser, the drier, or the compressor. when you put the oil in, i usually disconnect the low side line from the compressor and dump it in the line. that way it lubes the compressor first since the system has been flushed and is dry