1. Where is a/c relay so I can override compressor then add r134?

    I've been searching google for hours and it's weird I cannot find where the a/c compressor relay switch is so that I can override it (ie cause the compressor to kick on) so that I can then add a can of r134.

    Can someone please tell me where it is and how to override it?

    Thanks much!

    2011 Jeep Liberty

  2. #2
    Join Date
    Apr 2013
    Location
    Staten Island n.y.
    Posts
    2,000

    Re: Where is a/c relay so I can override compressor then add r134?

    Welcome to jeeps.com . Your jeeps power distribution center will have a relay which should indicate its for air conditioning or marked clutch relay. Look for a fuse that powers the circuit as well. Always good to look for any blown fuses while PDC is open. There is one problem however , if the low pressure switch on the low side ( most likely on the accumulator) will not close because the freon level is low thereby not allowing current to flow to compressor clutch. If you were to read the wiring from the clutch relay with the cabin switch on , the relay terminal 86 should be live and terminal 87 as well but the low pressure switch interrupts it . That is what the switch is there for , to save the compressor from low pressure and starving it from lack of lubrication. In order to accomplish what your wishing to do , you would have to jump out the wires that go to and from the PCM . They are on the harness plug on the low pressure switch . Is this safe since its wiring that feeds back to the PCM ? I've done it but it's risky without a proper fused jumper for a computer circuit. Your best bet is to get a set of manifold gauges and charge through the low and high side with the engine off. You will not get the complete charge in until the engines running and compressor is on BUT you must ONLY charge the a/c system through the LOW side with compressor ON. The reason you would charge the low and high side with compressor off is to establish some kind of pressure to get the system charged quicker.
    I want to say this first . If your compressor is in good shape and the low AND high pressure switches are working and no issues with the cabin controls , the introduction of freon will build pressure and the low side switch will close enabling the compressor clutch. If your attempting to charge the system as I believe you are and the clutch isn't kicking on , unplug the harness connector and manually ground and power the compressor to find out if the clutch is good with the engine off. This is not an accurate test for a/c clutch health since it can fail with the engine running and system charged and all else working otherwise. But you'll want to know you can at least run the compressor to circulate freon (and oil) through the system. If you must jump the compressor manually of all else fails and system is confirmed low ( or why would you be charging it ) , my suggestion is to first charge the system through the low and high side engine off. You must use gauges for this. If the high side will not take the freon , close the high side gauge and only keep open the low and then attempt to jump compressor with engine on monitoring low side gauge . Do not charge over 40 psi . Freon will change from gas to liquid if it exits the charge can too fast . It's best to warm the can in hot water but do not exceed 125 degrees or the can WILL burst . Hope this helps . If in doubt and you've any questions , please post back.
    Although I am not certified in air conditioning recovery or charging , I've successfully done quite a few cars which includes flushing system , changing components , charging and some electrical diagnostics . Keep in mind , no matter how good we think we are , we still need a wiring diagram if we're not familiar with the vehicle.
    Never overlook the obvious . It's usually right in front of us

  3. #3
    Join Date
    Apr 2013
    Location
    Staten Island n.y.
    Posts
    2,000

    Re: Where is a/c relay so I can override compressor then add r134?

    In my last post , I wrote a lot of general procedure and theory but did not address your jeep in question. Since it is only four years old , we must ask why the a/c is low on charge . First , is the system confirmed to be low . Second , is the compressor failing or leaking . Has the rest of the system been diagnosed for leaks . A substantial loss of freon may have been accompanied with the loss of compressor oil. Whenever someone decides to charge their system and use freon with oil in the charge , there is a chance of adding too much oil to the system . While there are those who believe too much oil is better than not enough are not entirely correct. Oil is necessary to lube the compressor bit too much oil will clog the accumulator resulting in poor freon flow through the the system . Too much oil and too much freon floods the evaporator as well causing lack of expansion and diminished cooling. The oil charge AND the freon charge must be right . The only true way to fix the a/c system is to diagnose. Of course electrical must be confirmed to,work right but the lines , seals and components also. Late model vehicles evaporator and condensers cannot be flushed since they're usually NOT a cross flow design like older designs therefor the flush cannot be completely removed. No guarantee compressed air will get it all. Replacement is the only viable option no matter how expensive. Of the only leak found is the compressor front seal as typically is , replacement is inevitable. Look for signs of oil leaks at threaded fittings , along lines , firewall connections low and high , behind compressor clutch and take note to any scent of oil in the cabin vents. If you scent oil in the cabin , the evaporator fittings ( expansion valve ) or evaporator core is leaking. Lovely , I know. Not wishing the worst on you but if you've got any warranty as the first owner and Chrysler can repair this , maybe they can save you money . Saving money and Chrysler dealer is an oxymoron granted but extensive air conditioning repair/replacement is big$$. Evaporator core replacement typically warrants dash removal. Big job. Big bucks. You'll want to know what's wrong before you pay for repair or even fork,over a diagnostic charge. I respect you just want to get through the summer but I thought I would give details of what to expect if you've decided to keep this jeep and not sell it or lose on a trade in .
    Never overlook the obvious . It's usually right in front of us

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