AC pressure after changing compressor ????????

Discussion in 'General Chevy & GM Tech Questions' started by DAREDEVIL, Aug 16, 2010.


    DAREDEVIL New Member

    Hi, i need to know how much pressure i need to fill in my 1996 Suburban !

    It has rear AC aswell.

    Any help would be very much apriciated .


    PS, maybe somebody knows how much goes in a 88 Camaro also ???? LOL ( wifes car )
  2. MightyMax

    MightyMax New Member

    Did you add in oil to the COmpressor as well??

    And put a vaccuum on the system??

    If those are in place, it should take about 3 - 4 cans easily.

    Do it with manifold guages, then you can watch the pressure build, and stop when it gets to 40 - 45 Low side.

    I don't believe the fact of having rear air makes a difference, but I could be very wrong on that assumption.

    ---------- Post added at 11:21 PM ---------- Previous post was at 11:19 PM ----------

    If you put on a new compressor and therefore the system is empty.

    If not done as well, change out the accumulator and the orifice tube.
  3. murdog94

    murdog94 New Member

    X2... And yes 40 -45 MAX PSI depending on temp, which most of the R134a cans have a temp guide, on what the proper charge is for the ambient temp.

    DAREDEVIL New Member

    Thank u all, but i have a 30# can and REAL gauges to fill the AC , also yes...oil in and vaccum done..-28 !!!!
    but @ 45 PSI my compressor wont even turn 65 it will work fine...??????????????????????????mmmmhhh
  5. murdog94

    murdog94 New Member

    Seems that your high pressure switch has had it. And you are at 45PSI on the low side with the compressor running? not to be stupid just confused because i know that real guages allow for more accuracy. but you should have a 3lb system. So i would have installed 3lbs and gone from there. but that is why i am confused because your low side should be 45lb with the compressor engaged. If the compressor is off then it isnt sucking on the low pressure site to lower the system pressure.

    DAREDEVIL New Member

    When the compressor is running it reads 55-60 PSI on low and about 250 on high !!!!after turning it off, it reads 75 on both !!! mmmmmhhhhh I'M LOST ..LOL

    Tomorrow i will bring it to an AC shop and let them figure this SH[T out..hahaha

    98 degree down here today ....sweting my a$$ off.
  7. murdog94

    murdog94 New Member

    Hmm sorry man. Confussed is right.. Is it cold at least?? And do you know how many lbs of R134a you put in? But it really seems like you have a bad high pressure switch. And or else a low pressure switch depending on which you are jumping to get the compressor to run...

    DAREDEVIL New Member

    Not jumping any...just filling it untill ~ 60 and then it comes on !!!!! and yes its cold but i still have a small leak in my thats why i filled it new ( i thought i fixed the leak ) THOUGHT !!!!!! is the main I found out that J&B weld is not strong enough on aluminum AC pipes...hehehe
  9. murdog94

    murdog94 New Member

    WEll thanks for the insight.. and that may be some of your issue is a the leak may not be allowing the proper pressure at the actual switches.. But i would lean twards a bad low pressur switch then. Since it is supposed to tell the compressor to kick on when you obviously have enough pressure.

    DAREDEVIL New Member

    THANKS, i look into it !!!!
  11. MightyMax

    MightyMax New Member

    Yeah, I agree 60 PSI is really high for the Low side.
    I would say your pressure switch on your Accumulator (maybe different on your truck compared to mine) as well.

    One other thing you can try is letting out some of the freeon...and then jumper the compressor to see if you can get it to ~45PSI
    Then see if it blows cold....
  12. Quincy

    Quincy New Member

    I have not done this in a few years but it sounds like you have it about right. Go to another vehicle and put the gage on when the motor is off then start the motor and see what they are running. as long as they are both the same refrigerant you are ok. Dont worry about the rear air or the leak as long as it is real slow. It eventually will have to be fixed but a slow leak will not stop you from charging the unit. If you put the righ pressure when the motor is off and when you start it the pressures dont match the control vehicle you will have to check the evaperator coil for dirt, or fan motor. [Which should be on high.] Or the fan belt. The suction line [large line] should be very cold to the touch but not so cold that it frosts up.

    Good luck.

    Last edited: Aug 17, 2010

    DAREDEVIL New Member

    Thanks much !!!!! and welcome to the site !!!!!!
  14. Quincy

    Quincy New Member

    Thank you and keep me posted on your progress.


    DAREDEVIL New Member

    Thanks for all of your help , AC WORKS !!!!!!!!!!!!!!!!

    But ofcoarse now i have a new problem....hahaha, WATER PUMP !!!!! and how the hell do i get the fan off ??????? Is that thread on there left or standart ????

    ANY HELP WOULD BE AWSOME !!! LOL, damn truck,,,but i love it ..HEHE
  16. murdog94

    murdog94 New Member

    I believe it is left handed.. Not 100% but that is reverse of rotation...

    DAREDEVIL New Member

    GOT IT !!!!!!!!!!!!!!! build me a nice tool , 2 holes and a little cutting and tool was done !!! BTW, the thread is standard rotation !!!! water pump works fine, all sealed up and AC is working aswell, changed to a billet distributer and everything works, only thing is it pops the code for the cam sensor and i dont know why..LOL
    after i delet it its fine , shut it off and back on, code showes ...MMMMMMMHHHHH ..oh well. !!!!!!!!

    Thanks for all of your help guys !!!! Anything i can help, just ask !!!!
  18. starsilverado

    starsilverado New Member

    In dealing with your AC problem. If you pulled a vaccum on your system while still having a leak then you pulled air and moisture into the system. you could have non condensables in the system causing the weird pressures. You need to fix the leaks, pull a really good vaccum and weigh the charge in. There should be a label under the hood stating the proper amount of refrigerant to put in. The rear AC could take upto an additional pound it will say on the label how much for just the front AC and the total for the front and rear. Also the low pressure switch will open at say 40# (not sure exactly what it opens at) then there is a differential before it closes again it maybe 60# again not exactly sure. It sounds like the switch is working properly. The main thing is a leak free , clean, dry system and weigh the charge in.
  19. MightyMax

    MightyMax New Member

    If you think you have a leak.
    Pull the vacuum and let it sit over night (24 hours) then put the guages back on and see if the vacuum is still there.

    DAREDEVIL New Member

    NO LEAK....but a lot of **** in the system i orfice tube is glooged up and changed it now we see...i have know how no problemo ...i can fill and all that in my sleep now...hahahahaha

    THANKS FOR THE HELP GUYS !!!!!!!!!!!!!!

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