Engine Size: 5.0
Refrigerant Type: 134
I have an 88 Mustang that I'm trying to get the AC working in again. It would cycle, but not blow out cold air. I flushed out the evaporator with a flush agent and water hose until it came out clean, then blew the remaining water out with air. Seemed good. I removed the compressor and flushed it out with Pag46 until the new, clean oil started coming out. Seemed good. I then replaced everything else. New high side line, condenser, liquid line with orifice, accumulator and low pressure switch. I replaced all o-rings with the new green o-rings and used Nylog on them before putting everything back together. I gave him my notes regarding setting the low pressure switch at roughly 21 for the 134 vs. 25 for the 12, and the conversion from 12 to 134 was 36 ounces. I was told the high side was approaching 500psi (I didn't get the numbers on the low side) and that there is most likely a blockage someplace in the system. I removed the high side line from the compressor and the liquid line from the condenser and blew air right through. This tells me the high side line and condenser should be ok. I also can blow air through the evaporator and accumulator. When I try to blow air through the liquid line with orifice tube, I get very, and I mean VERY little air through it. How much air can I expect to get through this line when checking with an air compressor? Is it possible maybe a paint flake or something similar could have come out of the condenser and clogged it? I'm not sure what the inside of the orifice tube looks like, but its all I can come up with, even though its new. Do I have any other things I can check other than just buying another new liquid line?
I was also just thinking that could the high pressure have anything to do with my fan? The clutch fan is gone, and has an electric in its place. It only comes on with the temp. sensor in the rad. I can wire it up to work with the AC compressor, just haven't done so. Could this lack of airflow through the condenser at rest cause the high pressure to go that high?
Edited: Sat September 08, 2012 at 10:34 AM by cs
You can't run a condenser with no airflow. The high side will rise out of control. Really your A/C mechanic should have noticed that and told you to fix the fan.
Conversion to electric fans are often inadequate, it takes a lot more air for good A/C performance than what it does to keep the engine from overheating. This is especially true trying to use 134a in an old-fashioned tube and fin condenser originally from an R12 system.
Edited: Sat September 08, 2012 at 11:07 AM by mk378
Ok, so I will wire my fan to work with the AC compressor. That's not a big deal. Is that really going to lower the high side that much, though?
I have a new condenser, its not the old style that originally came with the car. Its the new style designed to work with R134a refrigerant.
The stock clutch fans on the Fox Mustangs were not very good, and provide little cooling at idle, which is when most engine over-heating will occur. This is where the electric fan comes in and is a nice upgrade.
Did you really flush with water?
Only flush toilets with water-- NEVER an a/c system!
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
Most flush agents (not all) are volatile solvents that are removed by forced evaporation. This is done with a dry air or nitrogen "blow". Water should never be used as a flush or a rinse. The desiccant (filter/dryer) in a system is designed to remove only a few drops of water, which is anticipated to be introduced as the moisture contained in atmospheric air (i.e. humidity); and in very high humidity environments, these filters can become near saturation just during the installation process. I would recommend you restart the flushing process and do it properly. More details regarding this topic are in my signature below.
Operating the A/C system without the fans running will rapidly elevate the the high side pressures as the heat is not being rejected. The high side pressure/temperature is regulated/controlled by this heat removal.
You could air flow test (measure CFM) a few new high side lines w/ OT, to establish a norm; then you could flow your line to confirm if a problem exists or the restricted flow is somewhat norm.
Thanks. I got the fan put in last night, I'm just waiting on my upgraded alt. (which I now need to run 2 electric fans) and then I'll have the shop try it again. Thanks for the help, appreciate it.
I'll let you know what happens.
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