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08 Ram Pressue Questions

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  • 08 Ram Pressue Questions

    DIYer here. I have manifold gauges, vacuum pump, recovery pump and cylinder. I just replaced the evaporator, accumulator/drier, orifice tube on my truck, which is a 08 Dodge Ram 2500. I had an evap leak and heater core issue. While I had the plenum out I rebuilt the entire thing in hopes of not having to remove the dash again in the near future. The truck says it holds 1lb 11oz of refrigerant, I have refilled it with what should be the proper amount but I can not get my pressures and temps right. According to a r134a pressure chart @ 85deg I should have pressures in the range of 45-55 on the low side and 225-250 on the high side. I am more like around 35 on the low side and 175 on the high side. When I check my superheat and subcool temps I have the following. Subcool: gauge on high side reads 175 psi which equates to around 120 deg on the PT chart/gauge. My line temperature at the high pressure inlet is only around 93 deg. I have seen it up around 100 but not more than that. Superheat: low side pressure is reading around 35psi which equates to around 30 deg on the chart/guage. My lines at my evaporator are running around 47deg, which puts m y subheat at 17. I did manage at some point to get my evap temps down to like 42 and the truck was cooling great sitting at idle, but when I drove around the block by the time I got back to the house I had 65 degree air coming out of the vents. I figured at that point, I may have overcharged it so I evacuated a little with my pump but no dice. The best I’ve been able to achieve are the numbers above with 50 degree air blowing out of the vents while idling in the yard and driving around the block. What do I need to check next? It seems to me my out put side of my compressor may not be doing what its supposed to be. From what I can tell my condenser is only dropping temps of lines, at the most 10 degrees from input to output. My condenser fan runs as it should. One thing I noted is my compressor never seems to shut off. Once the system has enough refrigerant in it to activate the clutch it runs as long as I have the ac on, no cycling at all. Is that correct? Thanks for any help you guys can offer.


  • #2
    Clay, Welcome: Pls go easy on one run on sentence hard to take that all in. I don't see what condition "O" tube was is telling of compressor getting lack of lube. Know that oil doesn't flow well if compressor operates too long with a low charge tosses debris along that doesn't flush out like condensers too.

    Take a look at old one or evacuate now see what new one looks like there was no mention of flushing this or what it looked like think that's the problem all over again is just too possible if not really checking everything or tossing them again and again if not done.

    The clue was it worked around the block once and now all messed up again take a look at old then at new "O" tube if clogged it's start all over again IMO.

    Pics of new and wrecked "O" tube below. (no, it wouldn't show just look at many failed ones here,

    Last edited by Tom Greenleaf; 07-03-2018, 11:58 AM.
    MetroWest, Boston


    • clsmith29
      clsmith29 commented
      Editing a comment
      Thanks Tom. I didn't look at the old Orifice tube because it was made into the line going to the Evap. I still have it and can cut it out and take a look though. Being that it's made into one of the lines, I can't really look at the new one without destroying the line. I did fail to mention, I found where replacement of accumulator and Evap called for 2.5 oz of oil, so I did add that back to the system.

  • #3
    Oil guessing is almost impossible most would drain parts, measure what they get out plus a couple oz. if total capacity is about 8 or so. Little over OK, lot under is fatal to the system.

    Take a look or even blow backwards see what comes out. That's important info on how you'll approach the job if only some "O" ring was leaking or even the service ports on some wipe out a system over it.

    Just other while here till you can check is oil you catch it and an accumulator or any kind of drier you heat up and drill a hole in it see if more comes out for the guess remains a guess just gets you closer. Start with the check and let's go from there. You've touched the charge you thought was spot on now that has to go back to a known charge weight again is also the best info to find what's wrong. It worked you said just not long smacks of compressor so far but keep your hopes up then you need your work all over again - it stinks, no room for errors,

    MetroWest, Boston