kevinC Posted July 2, 2006 Share Posted July 2, 2006 I think I might have a restriction somewhere in the system. It takes several minutes to slowly equalize pressure once the ac is shut off. Do these cars have a fixed orfice or are they variably controlled with a thermo bulb. Also wondering if filter dryer might be plugged? Quote Link to comment Share on other sites More sharing options...
OB99W Posted July 3, 2006 Share Posted July 3, 2006 I think I might have a restriction somewhere in the system. It takes several minutes to slowly equalize pressure once the ac is shut off.If there's a performance problem, what is it? I'm assuming you've had manifold gauges attached; what are the readings? Do these cars have a fixed orfice or are they variably controlled with a thermo bulb. Also wondering if filter dryer might be plugged?They have an expansion valve; the valve could be icing internally if there's more moisture in the system than the dryer's desiccant could handle. Or something else might be restricted. Do you see any excessive external sweating or frosting? If so, where? How often is the compressor cycling (clutch engaging/disengaging)? Ambient conditions? EDIT: I see that we've been down this path before: http://www.ultimatesubaru.org/forum/showthread.php?t=58953 Kevin, may I suggest that rather than starting a new thread when the topic is still the same that you just add to the old one? Also, responses to questions might help us help you . Quote Link to comment Share on other sites More sharing options...
kevinC Posted July 3, 2006 Author Share Posted July 3, 2006 When I Rev the engine up the high side wants to climb up in the neighborhood of 350+ while the low side sucks down until it cuts out around 30. At idle it will short cycle with the blower at low speed but seems to do alot better with the blower speed on max. With the blower at low settings it will short cycle about ever minute, sucking the low side down till the switch is made. With the blower at high speed it will run ok at idle. I just finished cleaning the evaporator coil and it was about 30% blocked. This may help but I think either the filter is clogged or the expansion valve is not functioning properly. Also once the ac is shut off how long should it take to equalize? Also it will stop cooling completely if I let it idle for a long while. I think it is icing up and triping the thermo switch. I also apologize for starting a new thread but I couldn't find the old one. Quote Link to comment Share on other sites More sharing options...
nipper Posted July 3, 2006 Share Posted July 3, 2006 tis ok, sounds like there may be moisture in the system. What does your site glass look like, and what is the temp at the ac vents. nipper Quote Link to comment Share on other sites More sharing options...
OB99W Posted July 3, 2006 Share Posted July 3, 2006 When I Rev the engine up the high side wants to climb up in the neighborhood of 350+ while the low side sucks down until it cuts out around 30.The high side is definitely too high. It would still be helpful to know if there's any external (visible) sweating/frosting, and if so, where. The high side should be warm/hot (be careful touching!); if part of the high side is cool, that would indicate a restriction. At idle it will short cycle with the blower at low speed but seems to do alot better with the blower speed on max. With the blower at low settings it will short cycle about ever minute, sucking the low side down till the switch is made. With the blower at high speed it will run ok at idle. I just finished cleaning the evaporator coil and it was about 30% blocked.You might want to verify that the blower air is being properly deflected over the evaporator. Also, that the condenser fins are clean (not blocked by insects, etc.) and undamaged, and that the fan operation is correct. This may help but I think either the filter is clogged or the expansion valve is not functioning properly. Also once the ac is shut off how long should it take to equalize? Also it will stop cooling completely if I let it idle for a long while. I think it is icing up and triping the thermo switch.What service has the A/C seen previously? The high pressure could be due to excessive refrigerant charge or a contaminated system, etc. I also apologize for starting a new thread but I couldn't find the old one.No need to apologize, it's just that it makes things easier to follow if everything is in one place . The search function can be used to find previous posts. Quote Link to comment Share on other sites More sharing options...
SaltCar Posted July 3, 2006 Share Posted July 3, 2006 I second the advice on cleaning the condenser. Read about cleaning aluminum and get it spottlessly clean but be careful not to hurt it. Some cleaners attack aluminum. High pressure cleaning will bend the fins. Look at this site for information on diagnosing your system by gauge readings. http://www.perrinmfg.com/content/8x2.php If someone added refrigerant to the system when it was low and didn't pull a vacuum on it, suspect air in system. It can suck air into the system even when it still has pressure in it. The low side will pull down to a vacuum on a low system. Quote Link to comment Share on other sites More sharing options...
kevinC Posted July 4, 2006 Author Share Posted July 4, 2006 The bigger hose on the compressor(hot gas) is slightly cool and slightly sweating. The small line(High pressure liquid) is very hot. Seems to be worse after long idles. I think the evaporator is turning into a big block of ice. I think I will try replacing the filter at this point. Also checked and cleaned the coil through the blower motor resistor hole, everything seems to be clean now. I think there has to be a restriction somewhere, I have never seen a unit equalize so slowly after shutoff. Has to be the filter or the expansion valves. At least I know the check valves are working great inside the compressor. Quote Link to comment Share on other sites More sharing options...
nipper Posted July 4, 2006 Share Posted July 4, 2006 how does your compressor sound? nipper Quote Link to comment Share on other sites More sharing options...
kevinC Posted July 4, 2006 Author Share Posted July 4, 2006 sounds good. no sraining or sounds of over pressurizing. Really leaning towards a long vacuum and a new filter. Quote Link to comment Share on other sites More sharing options...
nipper Posted July 4, 2006 Share Posted July 4, 2006 i was just wondering about the source of the clog. Replacing that valve can be a PITA nipper Quote Link to comment Share on other sites More sharing options...
kevinC Posted July 4, 2006 Author Share Posted July 4, 2006 I was thinking maybe the normal wear from the clinder walls of the compressor and possibly other wearing items inside the compressor have slowly plugged the filter over the last 200,000. Got to try something or I am going to lose the clutch or something else from exsessive cycling. I have a new 30 pound cylinder of 134a and am ready to try something. Quote Link to comment Share on other sites More sharing options...
nipper Posted July 4, 2006 Share Posted July 4, 2006 I was thinking maybe the normal wear from the clinder walls of the compressor and possibly other wearing items inside the compressor have slowly plugged the filter over the last 200,000. Got to try something or I am going to lose the clutch or something else from exsessive cycling. I have a new 30 pound cylinder of 134a and am ready to try something. If your going to replace the filter. you need to evacuate the ssytem. As long as your doiung that pull the valve (i looked it up its not horrible to do) clean and test it. nipper Quote Link to comment Share on other sites More sharing options...
kevinC Posted July 4, 2006 Author Share Posted July 4, 2006 Looks like a couple of lines and a few bolts and the whole box will drop out. Any suggestions on how to check the valve. Quote Link to comment Share on other sites More sharing options...
nipper Posted July 4, 2006 Share Posted July 4, 2006 it should be fairly easy. Its a bulb. Imerse the bulb in cold and hot and see if the vave moves. You may even be able to see if the valve is clogged. I am used to valves on RR cars, so they were huge and easy to see. If the valve is stuck open, you will have equal pressures, if it is stuck closed, you will have extreem differnces in pressures nipper Quote Link to comment Share on other sites More sharing options...
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