QuestionQUESTION: I have a 1997 Buick Lesabre that is low on refrigerant (45psi on both sides equalized) The compressor won't run and I'm trying to figure out the best way you pros do this, ie getting the compressor to run via bypassing the low pressure switch. It has only one low pressure switch and it is a 3 wire logic setup, with the sensor looking on the wiring diagram like an operational amplifier. It gets a 5 volt reference and a PCM signal out, and also a common, into the sensor. I'm afraid to start jumping a logic signal that feeds the PCM (computer module) for obvious reasons, but I know there's got to be a way to get the compressor to run since there are millions of these 3.8s out there and AC pros like you have to be able to get the compressor to run in order to get the refrigerant in. Can you help...Thanks a million!
ANSWER: Eric,
Not to insult your intelligence, but are you certain that you are looking at the low pressure switch? The low pressure switch should only have 2 wires coming out of it. All it does is close contacts when pressure inside your line is above 17-22 psig and sends 12volts on towards your compressor clutch. This circuit gets it's ground from the clutch ground. I have never in 16 years seen a low pressure switch with 3 wires. But, I have never had my hands on a lesabre, either, so this may be a new one on me. Now, the high pressure switch will have 3 or, more often than not, 4 wires coming from it. This switch not only cuts out your compressor in the event of high pressure but also controls your condensor fan(s).
Just to double check, I will tell you how to find your low pressure switch on most vehicles. It wil be located on your low pressure line of course. Either in a hard portion of the line itself or on your accumulator. Your accumulator is an aluminum canister roughly the girth of a soda can with two hard lines protruding up from the top of it. Typically it is on the passenger side of the engine compartment near the strut tower.
If you were looking at the wrong switch and have found this one that I am speaking of, simply unplug the wiring harness from it and with an insulated wire jump the contacts in the harness plug. This should cause your clutch coil to energize and you will hear it snap as it engages.
I hope that I was able to help a bit. If you still say that your switch has 3 wires, I will gladly do a little more research and find out some information for you. Just, fact of the matter is, I have never seen one with three wires.
Thank you for the question and if I can do anything more just let me know.
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QUESTION: well i dislocated my elbow yesterday, so hence no response fom me. however it's a pressure transducer, and i believe it monitors both too low and too high pressure on the low side. it's not on the accumulator, but in the suction line.
AnswerEric,
Sorry to hear about your elbow. I did my shoulder during OIF 3, and I know the pain you feel.
Ok, I spoke with a couple of my peers today here at the school house, and they said that it should not affect the PCM in any way if you jumped it. They stated that they had only seen this setup in a couple vehicles during their experiences, and just tried jumping the different terminals until it kicked in. As I stated, I have never done it, so I won't swear by it.
Another option to you is charging it on the high side as a liquid. To do this, naturally you would need a connector that would fit your high side port. The only differences in doing this would be as follows.
The vehicle is OFF. Heat the can up under hot water (not an open flame) this raises the pressure inside the can so that it is greater than that within the system. Turn your container upside down so that liquid goes into the system rather than vapor. Once you have enough charged this way to enable your compressor clutch to engage or at a minimum cycle on and off, then you finish charging on the low side. It will not take much to get enough in for the compressor to begin cycling. If you put in more than about 6 ounces in this manner and your compressor still does not cycle, then there is something else going on in your electrical portion of the system.
Understand... DO NOT charge it on the high side with the vehicle ON. Charge some, disconnect your gauge, turn the vehicle on and see if your compressor beigns engaging. If it doesn't, turn the vehicle off, allow about 5-10 minutes for the pressures to equalize again, and charge a little more.
I am sorry I wasn't able to give you a definitive answer on how to jump it. But as I stated, I have never had the experience with a setup that you speak of. Thank you for the question though, it gave me a homework assignment to better educate myself on this type of switch setup.
