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A/C issues on 84 C10 with 5.3 LS

Discussion in 'Tech Discussion' started by shortboxin, Jun 2, 2020.

  1. shortboxin

    shortboxin Junior Member

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    I know, I know. A lot of info, but without it you won't know what I'm dealing with.

    Evacuated and charged the A/C system on my 84 C10 and I'm having issues that I've never experienced before on any vehicle. Of course, it's a kluge, so I should've expected to run into some problems. It cools, but no colder than 82° at idle and it's got very high pressures. System was previously converted to R134 with the 305 engine and worked fine until I opened it up last August to swap in my 5.3 LS engine.

    Setup:
    Aftermarket fans with shroud which turn on when A/C is switched on (not the compressor cycling)
    OEM evaporator
    OEM condenser
    NEW accumulator
    NEW Sanden SD7B10 compressor
    NEW custom suction and discharge hoses
    NEW orifice tube

    Blew as much oil as I could out of the evap and condenser since I don't know what was in it. Connected the hoses, but not until I added 6oz of PAG 46 into the system in various locations. Evacuated the system using a vacuum pump from Autozone. Pulled down to 28" of vacuum and left it for an hour.

    Started adding R134 with an outdoor temp of 94° and a jumper on my low side switch until I got 12oz into the system. Pressures at that time with clutch engaged:

    LOW = 28PSI
    HIGH = 160PSI

    Added my second can of R134. Low side jumper removed, but clutch was engaged 100% of the time as the pressure was too high for it to ever cycle off. Pressures now at:

    LOW = 60PSI
    HIGH = 230PSI

    Added most of my third can of R134, but quit due to the high pressures. Probably added 8oz or so. This means I only have 32oz of R134 in the system at most. From what I can tell, capacity is 44oz with R12, so it's technically still 20%-25% low... Clutch still engaged 100% of the time. Pressures now at:

    LOW = 90PSI
    HIGH = 330PSI

    Outside temp had climbed while charging and was around 98° by the time I finished. Interior vent temperature at idle is around 78° (give or take a few degrees), so not working too well. Drove the vehicle on surface streets as well as the freeway. Vent temp dropped to around 58°, but still not great considering.

    Any ideas on the cause for the high pressures? Thanks in advance!
     
  2. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Hmm, what orifice tube did you use, fixed or variable? What was the oil pre-charge of the new compressor out of the box, and was that six ounces in addition to that plus the residual amount in the evaporator and condenser?
     
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  3. shortboxin

    shortboxin Junior Member

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    Hey, thanks for the feedback!

    Definitely fixed, just like the OEM.

    Didn't know that the compressor might be pre-charged. No info came with it when I ordered it online. It's actually a knock off Sanden. Made an assumption that it had no oil in it besides assembly. Could it be that there is too much oil in the system?
     
    Last edited: Jun 3, 2020
  4. yevgenievich

    yevgenievich Full Access Member

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    All new sanden compressors come with oil already added SP-15. Only for larger systems usually more is added or compressor drained first. Very often some compressors(non factory sanden) will come with oil that should be drained before adding correct oil.
     
  5. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Over-oiling is definitely a no-no, but it sounds like there may have been oil in there for transport that you needed to drain off according to the above info so that could be worse in terms of cooling efficiency. If there was no information provided regarding the oil that’s in there, it’s imperative that you drain the compressor and add the correct oil.
     
  6. shortboxin

    shortboxin Junior Member

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    Based on what you guys are saying, I'm thinking it had oil added. Will separate system, blow out evap, empty out compressor, and drain out new accumulator. Thinking about adding a parallel flow condenser while I'm at it. Once system has been drained, how much should I put in? Full system is supposed to be 8oz, but even a drained compressor, accumulator and evap will still have residual oil...
     
  7. yevgenievich

    yevgenievich Full Access Member

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    Parallel condenser might not be as needed in a single cab truck. It helped for my suburban but that was with dual ac system. Accumulator will trap oil even if drained. Hard to tell how much. New accumulator and system flushed with ac flush will get it back to zero. I have uploaded the guide here and there are instructions on how to test for right amount of oil when working with unknown amount.

    https://www.gmsquarebody.com/threads/sanden-service-guide.22419/

    Screenshot_20200603-114800_Adobe Acrobat.jpg
     
  8. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    I agree, flushing is the only way to zero it out minus the compressor, but I think that’s a negligible amount left behind once you drain it. I would be tempted to hold onto the accumulator, too, but I know that’s not the best idea because, as mentioned, it’s impossible to get it all out, and there’s no way of knowing how much went in there net.
     
  9. shortboxin

    shortboxin Junior Member

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    Opened up the system this morning and collected all of the oil that I could. Got some drips on surfaces, floor etc. Removed the condenser, tipped it and blew it out, blew out the evap, dumped out the accumulator (stored it upside down for 2 hours and kept tipping it), and dumped the compressor while rotating it four separate times. Still only able to collect just under 3oz total.

    In addition, the 7B10 compressor doesn't even have a fill hole, so when I initially installed it, it really only had residual oil in it from assembly.

    At this point, I'm totally dumbfounded. I though for sure this system was going to be majorly over-filled. Don't know where to go from here.
     
  10. shortboxin

    shortboxin Junior Member

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    1. Flushed out the evaporator and hoses. Removed the condenser and flushed out.
    2. Changed the orifice tube to the .062" RED.
    3. Replaced the accumulator and added 6.5oz of PAG 46.
    4. Evacuated the system for about 5 hours.
    5. Charged the system with almost 3 full 12oz. cans of R134.

    Pressures came down considerably this time and it cools a little better than before, even with an outdoor temp of 103° instead of 98°. Vent temp getting down to around 75° at idle.

    LOW = 63PSI (90PSI previously)
    HIGH = 275PSI (330PSI previously)

    Took it for a drive and the vent temp dropped as low as 52° on the freeway, so that's an improvement of 6° even on a warmer day.

    Additionally, the accumulator and suction hose was hot last time and this time it's nice and cold.

    FINAL THOUGHTS: 1. I will investigate to make sure my blend is porting all of the air across the evaporator. 2. I may also add a ball valve to the incoming heater hose line so I can close it off during summer. I believe this is as good as it will get without changing out the condenser to parallel flow.
     

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