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1997 Chevy Lumina 3.1 - Compressor wont enage
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dmcconnell
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Jul 23, 2012, 8:50 PM
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1997 Chevy Lumina 3.1 - Compressor wont enage
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Hello all;
As a starter, this post is cross-posted from another website, so I apologize for my redundancy but I am trying to ask around as much as possible!
First off, I have done extensive searching online the past few weeks and have yet to find a posting on any site that accurately depicts the problem I'm having, so if something has been posted before please forgive me as I did look but may have missed something! Some info..
I am in the process of selling my 1997 Lumina. In case it matters, the motor has been replaced with a 3.1 out of a 1998 a few years back, but everything else matched so I don't think it affects anything here; please correct me if I'm wrong.
Long story short, AC Compressor will not engage. If I jump the AC relay underhood the compressor will engage, as it will if I shoot 12v to the compressor itself. However, and maybe I'm testing something inaccurately, I havent been able to find any native power running to the compressor with AC on any of its settings. I have also tested the AC Pressure Switch and havent found any power source to it; nevertheless, I did replace the switch since everyone claims it is this that causes the issue. I then replaced the dash temp control unit- the car does have dual climate; still no result. The only other guesses I got were that the compressor itself was bad; therefor, at the recommendation of my shop, I replaced the compressor, evac'd and refilled the system to spec- still, no operation.
Temp gauge in the car works correctly so I imagine the ECT works as well, although I may be mistaken?
To the best of my knowledge from my limited research the AC in this car is operated by the PCM, which must read quite a few different signals 'in the green' to shoot power to the compressor. As I recall, this includes cooling fan operation, engine temperature below a certain value, throttle position sensor below a certain value, IAT below a certain value (?) and perhaps more... My best guess is that some or all of these values hitting the pcm are past their given threshold and thus the PCM isn't shooting a signal to the compressor to engage. Does this sound plausible? Also, is there any way to test this? Can I chek the PCM and see what signals are/are not correct, to save me the trouble of replacing EVERYTHING and simply hoping it works when I'm done?
I'm literally ripping my hair out at this point, as I have already bought and installed the compressor I have invested too much money to really throw in the towel just yet. I would really REALLY appreciate some advice or help here- I can't explain HOW thankful I would be, as nobody I know (professional or otherwise!) seems to know what might be the issue, or even how the PCM operates the AC in this car.
If you have any other questions for me please ask- sorry for the small book I've written but I wanted to be as thorough as possible!
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Double J
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Jul 23, 2012, 10:04 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Powertrain Control Module Controlled Air Conditioning (Chevrolet Only)
The air conditioning system uses a compressor with variable displacement. This compressor is referred to as the V-5 type compressor. The V-5 compressor meets A/C requirements without cycling.
The A/C compressor operation is controlled by the Powertrain Control Module (PCM) for the following reasons: - Improves idle quality during compressor clutch engagement.
- Improves wide open throttle performance (WOT).
- Provides A/C compressor protection from operation with incorrect refrigerant pressures
For a description of the system and an explanation of the components used, refer to SECTION 1B of the service manual.
The A/C electrical system consists of the following components: - A/C control head
- A/C refrigerant pressure switch
- A/C compressor clutch
- A/C compressor clutch relay
- PCM
When A/C is selected through the A/C control head a 12 volt signal is supplied to the A/C request input of the PCM. The A/C compressor clutch relay is controlled through the PCM. This allows the PCM to increase the engine idle speed just prior to A/C clutch engagement for better idle quality. In addition the PCM will command the cooling fans on during A/C operation. The PCM monitors the A/C refrigerant pressure. If the A/C refrigerant pressure, and engine operating conditions are within a specific calibrated acceptable ranges the PCM will enable the A/C compressor relay. This is accomplished by providing a ground path for the A/C relay coil within the PCM. When the A/C compressor relay is enabled battery voltage is supplied to the compressor clutch coil.
The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested, unless any of the following conditions are met: - Throttle greater than 90%
- A/C head pressure greater than 427 psi (4.27 volts) or less than 41 psi (0.35 volt) (as determined by the A/C refrigerant pressure sensor).
- Ignition voltage below 9.5 volts.
- Engine speed greater than 6900 RPM for 5 seconds.
- ECT greater than 121°C (250°F).
- IAT less than 0°C (32°F)
A/C Clutch Circuit Diagnosis should be used for diagnosing the electrical portion of the A/C compressor clutch circuit. When diagnosing the refrigerant portion of the HVAC system, refer to SECTION 1B.
A scan tool will be used in diagnosing the system. The scan tool has the ability to read the A/C request and refrigerant pressure inputs to the PCM. The scan tool can display when the PCM has commanded the A/C clutch ON. The scan tool should have the ability to override the A/C request signal and energize the A/C control relay.
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dmcconnell
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Jul 23, 2012, 10:14 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Perfect... It seems there is a way! I've taken the car to two different shops however and neither has mentioned this... Is this a dealer only tool? I have not seen the ac diagnostic feature on any obd scanner I have used so I imagine it is a specialized scanner... Any idea where to have it checked, and what estimated cost?
That in itself helps a lot! Thank you!!
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Double J
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Jul 23, 2012, 11:26 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Of course there is a way to test it
A high end scan tool is required, not just a code reader
Most quality repair shops/techs have them..
Of course the Dealer does also....Example would be a 'Tech 2' or equiv....
If the shops in your area aren't equipped to diagnose this then you may have to
go to the dealer
As far as cost,you'd be looking at a minimum diagnostic charge of 1 hour at most places
at their going labor rate..Here in Chicago ,avg shop is at or above $100 an hour, most dealers are $125.
With the right equipment/tools and understanding of the system,it shouldnt be that hard to figure out.
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Hammer Time
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Jul 24, 2012, 3:14 AM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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This is not a real complicated or uncommon procedure but you do have to understand electrical circuits and know how to read a wiring diagram. You never stated whether your system was Auto temp control or manual so I'm assuming it's manual.
Here is the wiring diagram for a manual system. What's real surprising is that I don't even see a pressure switch in the circuit.
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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.
(This post was edited by Hammer Time on Jul 24, 2012, 3:17 AM)
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dmcconnell
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Jul 25, 2012, 4:14 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Thanks to all the information provided so far!
I have yet to find a shop with the tech 2 scanner... Even the dealership I tried doesn't! I am tryin to avoid paying for the 150 they'd charge just To tell me the status of a few sensors though...
Looking at a wiring diagram it appears the PCM takes input from AC request at the control unit, as well as signal from the related sensors (tps, iat, etc) and then turns on the ac clutch circuit. My question- the wire running from the PCM to the ac relay: is it sending out voltage or is it providing a ground path? In other words, if I can't find this scanner, should I be checking the ac output from the PCM for power? Or should I be checking for ground? This might seem like a silly question but the way the diagnosis is worded confuses me.
Thanks again for all your continued help guys- I'm close to a solution!
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Hammer Time
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Jul 25, 2012, 4:16 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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I just gave you the wiring diagram.
The TPS and IAT have nothing to do with the compressor circuit
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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 25, 2012, 4:17 PM)
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dmcconnell
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Jul 25, 2012, 4:34 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Is that the right diagram? Everything I've read indicted it does.
In addition the diagnosis procedure posted just above mentions it...
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Hammer Time
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Jul 25, 2012, 4:38 PM
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If you have manual temp control, that is your diagram. If you have auto temp control, it's a different diagram but it still doesn't involve those sensors.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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dmcconnell
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Jul 25, 2012, 5:09 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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So that diagnosis sheet is incorrect and the PCM doesn't control AC activation? That goes against everythin I've heard everywhere else...
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Hammer Time
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Jul 25, 2012, 5:13 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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OK, it's apparent that you are having trouble reading a wiring diagram. That diagram clearly shows the PCM controlling the compressor relay by applying trigger ground once it is satisfied with control head request.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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dmcconnell
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Jul 25, 2012, 5:20 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Your condescending tone is kinda disappointing. Rather than just assume I have no idea what I'm talking about, why not try to understand what I'm saying?
Look at the diagnosis posted above by another poster. That is the same diagnosis sheet I've found time and again for this car (which is manual dual climate zone). It's also reflected in the wiring diagram I have, which does not match yours.
Everything i have read (including information poste above, which I keep asking you to reference...) indicates the PCM requires MORE than just a positive signal from the control head... It requires certain engine parameters in order to send signal to the clutch relay.
What frustrates me is I am trying my best to convey this mismatch of information to you to continue this process but you disregard what I am saying completely- in other words, yes, I can read a wiring diagram, to an extent, but Every other diagram I have seen does not match yours- I can post a picture if it helps. Do you see my frustration as I try to articulate and you berate me?
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Hammer Time
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Jul 25, 2012, 5:31 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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If you have a different diagram, post it here. I would like to see it.
The diagram I posted is the one released by the manufactured from a data base that i pay good money for. I just checked another source and found the exact same diagram in 2 different places. There is a pressure sensor involved but it reports to the control head before it makes it's request to the PCM.
If I were you I'd be testing to determine if the PCM is receiving request signal.
PS, You still haven't told us if it's an Auto temp or not.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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 25, 2012, 5:35 PM)
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dmcconnell
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Jul 25, 2012, 5:37 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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I am posting from an iPhone so can't upload a file; can I text or email to you? Otherwise I have to post later this evening.
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Hammer Time
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Jul 25, 2012, 5:39 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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I can wait. I'll be here until about 10PM EDT.
I just looked at the ATC diagram and the compressor controls are basically the same.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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 25, 2012, 5:40 PM)
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dmcconnell
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Jul 25, 2012, 5:50 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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All the wiring diagram business aside.... The diagnosis procedure still states that PCM requires iat, ect and tps sensors to reply in a given range to operate ac... What's up with that?
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Hammer Time
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Jul 25, 2012, 5:57 PM
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You're not getting codes for either of those sensors to indicate open circuit or high voltage which would be the only situation that could have anything to do with compressor controls so why are you worrying about it?
So far you haven't even checked to see if it's getting request.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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Discretesignals
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Jul 25, 2012, 5:59 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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The pressure sensor is actually an input to the PCM. It's in the PCM wiring schematics and for some reason doesn't show in the heater and ac section diagrams.
The PCM needs to know the IAT, so it doesn't turn on the compressor when it is -20 degrees outside( there is a value, but I forgot what it is). The PCM also uses the TPS signal to disengage the compressor during hard acceleration.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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dmcconnell
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Jul 25, 2012, 6:01 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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I haven't had the chance yet, and wanted to know what I was looking at first- while I may seem argumentative, I would MUCH MUCH rather be proven wrong and know exactly what I'm looking at than try and win an argument.
I'll test the PCM request circuit tonight and see if it's receiving anything. I'll also post that other wiring diagram when I can. Thanks in the meantime-
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Discretesignals
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Jul 25, 2012, 6:11 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Yes, it should set codes normally. Unless the IAT sensor signal is skewed, but within range. Not saying this is the problem with the OP's, but I had one a long time ago that had me pulling my hair out and it was the IAT sensor putting out the wrong reading causing the compressor to not engage.
You should follow HT's advice.
Don't attempt to jump the pressure sensor to get the compressor to engage. It's a pressure transducer and not a switch. You jump the wrong terminals and you can kill the PCM.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jul 25, 2012, 6:13 PM)
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dmcconnell
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Jul 25, 2012, 6:13 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Just to play devils advocate, of IAT Thought it was -10 instead of 100 it wouldn't kick on.. But I agree. I would think anything would kick a code. I've just tested a lot and even replaced the head unit so not sure (short of a cut wire) how it wouldn't be receiving request. I'll check tonight.
Edit: I did see it wasn't just a switch and against all (poor) advice I didn't try to jump it for that reason. I did however replace it with a brand new one to no effect.
(This post was edited by dmcconnell on Jul 25, 2012, 6:15 PM)
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Hammer Time
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Jul 25, 2012, 6:16 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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All this would be a whole lot easier with a high grade scan tool. All this info would be right in front of you. It doesn't have to be a Tech2, just professional grade.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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nickwarner
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Jul 25, 2012, 6:21 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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If you had a brand new sprinkler and a brand new house, you still can't water your lawn if the hose is pinched off. Thats why you need to verify signal by backprobing the PCM to see if it is getting the request from the control and if so backprobing the same connector to verify if it is sending the signal to engage the compressor. You have to see if the components are doing what they are supposed to. This could be as simple as a corroded connector pin or green death in a 1 inch piece of wire. Could be more expensive parts. But the only way to know what to do is to check it systematically to see where you have power and where you don't.
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dmcconnell
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Jul 25, 2012, 6:21 PM
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Re: 1997 Chevy Lumina 3.1 - Compressor wont enage
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Agreed wholeheartedly. Unfortunately nobody I know has one and I'd rather not spend $125 just for a scan
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