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2005 Chevy Cavalier AC out.

acquestionsacquestions Posts: 4
edited March 2015 in Chevrolet
I have a 2005 chevy cavalier and the ac went out recently clutch is engaging,  fans are working, and the freon is at the percentage for my areas temp. Low pressure line going to dryer is barely cool and the dryer and other lines are even warmer, any idea, I believe it may be the high pressure switch or some kind of blockages 

Comments

  • thecardoc3thecardoc3 Posts: 5,137
    If the system is working correctly the high side line, between the compressor and the condenser should be hot to touch, and if the system is really working hard, too hot to hold your hand onto. The line between the evaporator and the accumulator should be cold, sweating, just short of frosting. Did you have gages on this, or were you simply trying to use one of those DIY charging kits that only has a cheap little gage for the low side on the can? Even with an accurate gage, the low side reading alone isn't enough to judge what the system is really doing. For one thing the system uses a variable displacement compressor which internally regulates itself to run at 26-29psi on the low side. So the system could be under charged, or working exactly the way that it is supposed to and you would still see the same pressure. When tested with both high and low side gages the difference is easily seen on the high side between a system that is undercharged and one that is working correctly.

  • my gauges were not the diy, I had enough of those inaccurate things on a previous truck, and had my dad's help(professional mechanic), we did have a little high but got everything in line with the gm specs, when we did get both lines high and low gauged. low pressure cool bit not frosty as it should be and the other lines are about skin temp
  • thecardoc3thecardoc3 Posts: 5,137
    edited March 2015
    In the shop one of the first things that should be done right now is use an identifier and prove what is in the system. Non condensable contaminants (air) could give you the results that you are seeing. If the refrigerant isn't contaminated then recovering, evacuating, and putting in a known good correct charge would help prove what is going on. But that isn't necessary with full gage readings and by following this contact temperature testing routine that I will outline here.

    The sensible heat (what we measure as temperature or feel) is an important part of the diagnostics. The refrigerant entering the condenser should be some twenty to fifty degree's higher than what is leaving the condenser. The refrigerant leaving the condenser should be twenty to thirty degrees higher than the ambient temperature. The refrigerant temperature leaving the evaporator should be +/- five degrees what it is right after the orifice tube if you can reach it to measure it. There should be no more than one degree temperature change as the refrigerant passes through the accumulator.

    These measurements should be taken with the engine running about 1500 rpm, cooling fans on (fan in front of the condenser) The doors of the car open, MAX AC setting, full cold, high blower speed.

    Now based on the image with what you wrote, the temperatures that you are suggesting have the evaporator outlet more than five degrees warmer than the inlet, and the condenser inlet not hot to touch. That means you are not picking up heat in the evaporator (low side) and moving it to the condenser. Liquid refrigerant should still be boiling and absorbing heat all the way to the accumulator which is why it should be much colder than what you described. By it not being cold that means you ran out of liquid refrigerant and started adding super heat to the refrigerant which results in a temperature change of the refrigerant. Then when the compressor compresses the refrigerant, the fact that you didn't pick up much heat in the low side is reflected by not having a big increase in sensible heat on the high side.

    This is easily undercharged, the compressor isn't pumping correctly, the refrigerant contaminated, or all of the details haven't been provided and a first hand inspection of the system would reveal something that hasn't been mentioned.
  • we believe it may be the high pressure switch initial start up had the clutch engaging for about 2 seconds then stopping, after looking at a few things the plug that goes in to the switch was a two part plug and was half apart, slid clip back in place and compressor is engaging every time, taking it to my ac guy soon he's just out of town and really the only one around. Any other suggestions, based on some poking and prodding and searching (both with the ac system and researching online) Maybe a bad high pressure  switch, I don't feel the freon is to low, as stated we have good  gauges for both lines and just to be sure they were operating properly we looked at the pressure on his new Silverado and they were factory specs, we also believe it may be the orifice tube. Do the switch or tube sound viable?
  • thecardoc3thecardoc3 Posts: 5,137
    First with today's high efficient systems you want to avoid attaching gages unless you really need to do testing. The refrigerant that can remain in the gages that came from the car can easily cause the system to be undercharged just because it was checked. Many cars today have a full charge at just 14oz. The gages can hold 1.5oz in regular length hoses which means the system could be left 10% undercharged just because someone checked it.

    Today we start with a scan tool and look at the system pressures (temperatures) and the system inputs and commands before we do anything with the AC machine or gages. Now the fact that you mentioned the compressor clutch was not staying engaged, that is an important detail. You need to use a scan tool to see if it is being commanded off and if so what input is making the PCM do that.
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