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Compressor & Cooling Fans wont shut OFF
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TooMuchAC
Novice
Jul 5, 2011, 5:27 PM
Post #1 of 13
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Compressor & Cooling Fans wont shut OFF
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Hello - newbie here and I have an issue probably a little different than most seen posted ...
Car: 2002 Saturn L200 with the 2.2 Ecotec and 113,000 miles.
Just bought the car in December. The a/c didnt work then (as evidenced by turning on the defrost and the compressor not cycling in short bursts). I brought the car to the dealer and the condenser had a huge hole in it and only 8psi of 134a charge in the system. $500 later, and I have ice cold air!! 
However, when I turn the a/c OFF. Im talking the vents are in the face, the a/c button is OFF, and the inside blower fan is completely OFF, the compressor and cooling fans still run! They will turn on immediately when you start the car.
I replaced the HVAC head unit inside the car, figuring its shorted out somehow. No change. I bought a new a/c relay - no change.
I traced the wiring diagrams (backyard mechanic skill level here) to the main wiring harness. Apparently, the PCM will send a ground signal to the a/c relay and shut off the fans/compressor when commanded. Well, I ran a new wire from the main PCM harness to the a/c relay and no change - it still runs non stop.
Any advice is greatly appreciated.
(This post was edited by TooMuchAC on Jul 5, 2011, 6:29 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 5, 2011, 5:46 PM
Post #2 of 13
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Re: Compressor & Fans wont shut OFF
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What are you trying to shut off because you're not clear. The fan definitely should shut off but the compressor may be wired to run most of the time. That's pretty common now.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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TooMuchAC
Novice
Jul 5, 2011, 5:55 PM
Post #3 of 13
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Re: Compressor & Fans wont shut OFF
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What are you trying to shut off because you're not clear. The fan definitely should shut off but the compressor may be wired to run most of the time. That's pretty common now.
Im trying to get my compressor and cooling fans to stop running when I turn the a/c OFF.
It may be common on some newer cars these days, however its not common on this specific car. As a matter of fact, I have two Saturn L-Series and have been a long time owner of them. Ive been swapping parts from each car back and forth as a process of elimination regarding this problem. My other L-Series cycles and when you turn the a/c switch OFF, the compressor and fans turn OFF.
So with that being said, this is killing my mpg's. And Im concerned that with the compressor running non-stop that I might build up too much pressure on the high side.
Apparently the PCM sends a ground signal to the a/c relay to turn OFF the fans and a/c clutch. So to rule out a short, I jumpered the wire from the main wiring harness and there was no change. Im assuming the command to stop the compressor from cycling and the fans from running is NOT being sent from the PCM...
Any other suggestions, maybe something I am missing here?
(This post was edited by TooMuchAC on Jul 5, 2011, 5:59 PM)
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TooMuchAC
Novice
Jul 5, 2011, 6:12 PM
Post #5 of 13
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Re: Compressor & Fans wont shut OFF
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Apparently the PCM sends a ground signal to the a/c relay to turn OFF the fans and a/c clutch. No, it does not. The ground from the PCM turns the compressor "ON", not off so if you have a ground signal at that wire, then the PCM is intentionally turning it on. I don't know how identical your 2 vehicles are but you can have multiple system types within the same year and numerous changes from year to year. You don't understand the logic programmed into the circuit so you really should stop experimenting before you fry one of your computers. There are 3 different computers making decisions about the HVAC system and all it takes is one wrong move to fry one.
Thanks Hammer. Thats what I meant, but didnt word it correctly with the grounding. Glad you deciphered it!
I realize there are differences between the PCM/BCM - not to mention the different programming between VIN #'s, and would never swap those specifically. I have however swapped the fan module (same GM part #), the a/c relay (same GM part #) and the fuse (both 10amp) just to rule it out. The only difference between the two cars is the color. Ive been an L-Series owner since 2001 and have done just about every repair on them, sans a/c work because I lack a vacuum pump and recovery equipment. I can tell you most everything about L-Series aside from how to fix an a/c problem with them...lol.
However, I cannot imagine why the compressor and fans would both run constant after I turn the a/c request OFF and the blower fan OFF. Something is definitely amiss.
(This post was edited by TooMuchAC on Jul 5, 2011, 6:13 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 5, 2011, 6:17 PM
Post #6 of 13
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Re: Compressor & Fans wont shut OFF
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Just because you are not swapping computers doesn't mean you can't fry one. Many of those wires you are messing with are connected to the PCM or BCM and if you do the wrong thing with one of them, you can fry a quad driver that is only designed to carry less than an amp.
The circuit needs to be troubleshooted using a computer safe test light to determine why it's being powered.
I'm still not clear on whether it's the cooling fans or blower motor that you're trying to stop.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jul 5, 2011, 6:19 PM)
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TooMuchAC
Novice
Jul 5, 2011, 6:25 PM
Post #7 of 13
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Re: Compressor & Fans wont shut OFF
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Just because you are not swapping computers doesn't mean you can't fry one. Many of those wires you are messing with are connected to the PCM or BCM and if you do the wrong thing with one of them, you can fry a quad driver that is only designed to carry less than an amp.
The circuit needs to be troubleshooted using a computer safe test light to determine why it's being powered.
Again, it is the compressor and radiator cooling fans (Push & pull) I am trying to stop. The blower fan is already set to OFF and is NOT running. Yet, the compressor and cooling fans (Push & Pull) are still running as if a/c service was being requested from the inside of the vehicle.
Ok, so earlier I couldnt find my test light, I think I left it at work.
However, I did run a new run of wire from the a/c ground signal at the PCM harness to the underhood fuseblock, to the a/c relay. My purpose was ruling out a shorted signal ground wire from the PCM to the relay.
With the wire disconnected from the PCM, the compressor and fans did indeed shut off, as I expected.
With the new wire from the PCM ground signal connected, the compressor and fans run constant, HVAC controls set to OFF. Just like they would with the wire in the main harness. That tells me that the PCM is requesting a/c performance despite inside user controls.
I could go and pick up my test light out of my tool bag at work (1.5 hours of driving), but think that the jumper wire I ran pretty much rules out that the PCM is still commanding a/c for (whatever reason). Maybe a faulty signal from the BCM? who knows...
(This post was edited by TooMuchAC on Jul 5, 2011, 6:30 PM)
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Hammer Time
Ultimate Carjunky
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Jul 5, 2011, 6:29 PM
Post #8 of 13
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Re: Compressor & Fans wont shut OFF
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I think you're spinning your wheels. You have proven that the PCM has control of the relay and it has decided of whatever reason that it wants the compressor on. There is no problem with the compressor control circuit. The PCM could be getting a faulty signal from something else causing it to run the compressor as a result of that but you're going to need a professional scan tool to determine that.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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saturn tech
User
Jul 7, 2011, 7:04 PM
Post #10 of 13
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Re: Compressor & Fans wont shut OFF
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Are you sure the compressor is on? Is the check engine light on? If there is a fault for the thermostat (thermostat regulating temp) or the ECT, the fans will run all the time. Sorry I can’t remember the exact codes.
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Discretesignals
Ultimate Carjunky
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Jul 8, 2011, 9:08 PM
Post #11 of 13
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Re: Compressor & Cooling Fans wont shut OFF
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If you disconnect the ac relay coil ground circuit at the PCM and the compressor kicks off, you just eliminated everything after the PCM. The PCM turning the cooling fan and compressor on means one of two things. The PCM is getting the AC request command from the BCM and isn't supposed to or the PCM is faulty. You need to check the ac request data at both the PCM and the BCM using a high end scan tool to narrow down your search.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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TooMuchAC
Novice
Jul 8, 2011, 10:17 PM
Post #12 of 13
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Re: Compressor & Fans wont shut OFF
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Are you sure the compressor is on? Is the check engine light on? If there is a fault for the thermostat (thermostat regulating temp) or the ECT, the fans will run all the time. Sorry I can’t remember the exact codes.
Yes, the compressor is on. Verified by 1.) seeing it visually 2.) getting ice cold air through the vents 3.) Typical loss of engine performance while a/c is cycling.
There are no DTC's or check engine light.
My fans do not run all of the time. ONLY when the a/c is 'stuck' on.
I have found out that when the a/c will not turn off, I switch the HVAC selector from face to defrost mode, then in a bit when I can feel the a/c cycle off while driving, I hurry up and turn the blower fan off, then the compressor and fans will actually finally deactivate. Nothing else will turn the compressor and cooling fans off. BTW, the cooling fans and compressor run at the same time. Once the compressor turns off, the cooling fans turn off.
If I turn the blower fan on in any position (face, face/floor, floor, defrost/floor, defrost) withOUT the a/c on, then the a/c comes on and sticks on after that, even if I turn the blower fan completely off!
Im on vacation right now and the L200 is at home. When i get back, Im going to meet up with my friend with the TECH II but thats not until July 18 at the soonest.
Thanks for all of the replies folks!!
(This post was edited by TooMuchAC on Jul 8, 2011, 10:26 PM)
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