stokes Posted July 19, 2008 Report Share Posted July 19, 2008 Hi all,its been a couple of years since I've posted here,I guess thats a testiment ot how good a Caddy really is.Anyway my problem is with the air conditioner again.Its a '92 Seville.It had been retrofitted with 134 refrig. before I got it.The compressor seems to run intermittently.It blows cold sometimes and sometimes it doesnt,I assume the compressor isnt turning on.I got no error codes,so I evacuated the system,changed the orifice tube and recharged it.It seemed to be okay for a couple of days,now its back to the same thing.I had recharged it back in '05 or '06 and it was okay till this summer.When I recharged it last time I used a refrigerant that had oil in it.This time I used a refrigerant that didnt have oil.I am pretty sure there are no leaks,as it still shows the same pressure on the manifold gauge as it did when I refilled it.My question is,when evacuating the system,does the oil need to be replaced?If so how much should I use?Would too little or too much oil cause this symptom?I am about to evacuate it and recharge again.I have a 12oz can of refrigerant that has 8oz of oil and 4oz of refrigerant.I have seen charts that give different pressure levels that 134 will be at different ambient temps.i.e at 70degs it should be 35-40psi at 90degs 45-55psi.Does that mean if the outside temp is 70degs I should fill to the 35-40psi and 90degs I should fill to 45-55psi?Thanks for any help here. Link to comment Share on other sites More sharing options...
KHE Posted July 20, 2008 Report Share Posted July 20, 2008 If there is not a major leak and/or you did not replace a major system component, addition of oil is not necessary. Too much oil will affect the system performance - as it reduced cooling. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
stokes Posted July 20, 2008 Author Report Share Posted July 20, 2008 So evacuating the system doesnt remove any oil?Is there a way to drain some or all the oil and start from scratch?I assume the first time I recharged with the refrig./oil combo I added too much oil.The symptoms I have now arent just reduced cooling,it seems that it will blow cold sometimes and sometimes it is just warm air blowing,like the compressor is off. Link to comment Share on other sites More sharing options...
KHE Posted July 20, 2008 Report Share Posted July 20, 2008 A normal evacuation process (with a vacuum pump) does not remove any of the refrigerant oil from the system. If there was a large leak such as a stone puncture in the condenser there would be some oil loss. Are you sure the oil charge in the can was 8 ozs??? That is the total system capacity so if you used several cans of that it is possible that the system is clogged with oil. The only way to remove the oil is complete system disassembly and flush the lines. The compressor and accumulator would need to be removed and drained. Hopefully, you don't have to do that... When you charged the system, did you use a vacuum pump to properly evacuate the system? If not, there is air in the system which may be raising the head pressure enough to cut out the compressor. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
stokes Posted July 21, 2008 Author Report Share Posted July 21, 2008 I did use the vacuum pump to evacuate.I havent used the can that has 8oz of oil yet.When I recharged it 2-3 yrs ago I used cans that had some oil,but I dont recall how much,it wasnt 8 oz though.I dont think it gave an amount,I think the can just said "with lubricant" so maybe it was an insignificant amount.I checked the pressure yesterday and it read 64psi,so I released some to bring it down to 55psi.I am going by the chart I found that said at 90 to 100 degs ambient temp the freon should be 45-55psi.It seems to be blowing cold all the time now,but when I first recharged last week it was good for a couple of days and then started acting up again,I'll see how it goes for the next few days.I did change the orifice tube as well,so if it is overfilled with oil,will the new one clog up right away?I assume I can check the high pressure side at the same time as the low pressure which would indicate the orifice is clogged,no? Link to comment Share on other sites More sharing options...
KHE Posted July 21, 2008 Report Share Posted July 21, 2008 Oil won't clog the orifice tube - If the compressor is coming apart internally, the o-tube will clog up with teflon particles and/or metal particles. When I used the word clogged in my earlier answer, it was to indicate the amount of oil in the system if an additional 8 ozs were added. I should have used the word overfilled instead of clogged. You need to monitor the high and low side pressures simultaneously at the time the compressor cuts out in order to approximate the charge in the system. Do not go by static pressure (the pressure of the system when the engine is off). Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
stokes Posted July 21, 2008 Author Report Share Posted July 21, 2008 Okay,I've been monitoring only the low pressure side,and only while the compressor is running.Now if I monitor both high and low side and I see the low side is "in range" and the high side is low,do I add more refrigerant.The chart I have shows what the pressure on each side should be at various ambient temps.Thanks for your replies,KHE,very helpful. Link to comment Share on other sites More sharing options...
KHE Posted July 22, 2008 Report Share Posted July 22, 2008 Do you have a manifold gage set? That will allow you to monitor both sides simultaneously. Post the pressure readings and we can go from there. You should also monitor the vent temperature - set the climate control panel to AUTO 60 degrees and place a thermometer in the center A/C duct outlet. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
stokes Posted July 23, 2008 Author Report Share Posted July 23, 2008 Yes,I have the manifold gauges,vacuum pump etc.I dont have a thermometer handy,but I'll check both hi and lo sides and see if I can put my hands on a thermo. Link to comment Share on other sites More sharing options...
stokes Posted July 24, 2008 Author Report Share Posted July 24, 2008 Havent had a chance to hook up the gauges yet,but the AC seems to be okay since I recovered some refrigerant to bring the low side pressure down to match the psi to ambient temperature I see on the chart I found. Link to comment Share on other sites More sharing options...
KHE Posted July 25, 2008 Report Share Posted July 25, 2008 I'd be interested to see the high and low pressure readings, air temperature, and duct outlet temperature when you get the chance to hook up the gages. The temperature scales on the gages are not applicable for an automotive system. They are for stationary units and are used to calculate the superheat of the system. Off topic - In a home A/C or other stationary unit, the temperature of the suction line is monitored with a thermometer while the unit is running. Then the low pressure gage reading is converted to temperature using the chart (or the temp scale on the gage). The difference is the superheat. In a home A/C unit the proper superheat is a function of the ambient temperature. If the ambient (air) temp. is 75 degrees, the superheat needs to be 30-35 degrees. If the air temp is 90 degrees, the proper superheat is 15-20 degrees. When the proper superheat is aachieved, the unit has a proper charge of refrigerant. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
stokes Posted July 25, 2008 Author Report Share Posted July 25, 2008 I'm not talking about the temperature scales on the gauges.I have a chart I got from an AC suppliers web site that shows what the high and low pressure should be at various ambient temperatures.For instance at 80 degs low side should be 40-50psi,high side 175-210psi at 90 degs low side 45-55psi high side 250-270psi.When I first charged it up,I didnt have the chart,I filled it till it was about 55psi.That was when it was about 80 degs out.When the temperture went up over 90 degs a couple of days later is when it crapped out.When I found that chart I put the gauges on and my low side was about 68psi,outside temp was still over 90.I reduced the charge to match the prescribed temp/psi level and it seems to have worked so far,see what happens when we go over 90 degs again.I should have a chance to hook up the gauges this weekend,I'll post the results. Link to comment Share on other sites More sharing options...
stokes Posted July 27, 2008 Author Report Share Posted July 27, 2008 I am not able to check the high pressure side.Whoever did the retrofit didnt change the fitting on that side.When I bought the car from a dealer,I was led to believe it was done by the dealer,but I have my doubts.It appears the only thing changed was an adapter was fitted over the low side port to fit the 134 hose.I took a long ride this weekend,3hours out,3 hours back.The AC is working better,but it still fluctuates,at some points the air is absolutely frigid and sometimes it is just cool.This is while being run at max cool(60 degs) setting.Maybe a problem with the air mix door or the thermostat? Link to comment Share on other sites More sharing options...
KHE Posted July 27, 2008 Report Share Posted July 27, 2008 I would not suspect a blend door problem at this point - you most likely have the incorrect amount of refrigerant in the system. Why not buy a high pressure conversion fitting and install it so you can read the high pressure? Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
stokes Posted July 27, 2008 Author Report Share Posted July 27, 2008 I would not suspect a blend door problem at this point - you most likely have the incorrect amount of refrigerant in the system. Why not buy a high pressure conversion fitting and install it so you can read the high pressure? That thought had crossed my mind.Are they available at auto part stores? Link to comment Share on other sites More sharing options...
Texas Jim Posted July 28, 2008 Report Share Posted July 28, 2008 That thought had crossed my mind.Are they available at auto part stores? Yes... usually. Link to comment Share on other sites More sharing options...
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