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VT A/C problems Maybe due to custom tune???

Discussion in 'Mace Engineering' started by Nut Kracker, Jan 4, 2013.

  1. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Hi all.
    My 97 VT SS has had a custom chip installed. It's the first sequential 304 to have a mafless tune.
    My problem is....When I bought the car, to when it went in for the engine mods, I never had the air con going.
    After all the mods were done, we found that the air con was not working.
    The compressor works and blows cold air if the relay is bridged, but does not turn on normally. All the wiring, relays, gas pressure, pressure switch, A/C switch and blower have been checked and all ok. We haven't checked the BCM though.
    According to the Tech 2, when the A/C button is pressed, it comes on for 2 seconds and then goes off. Not enough time for the compressor to activate.
    What I'm wondering is, could the custom tune be some how interfering with the A/C operation?

    Your views would be much appreciated.
    Geoff.
     
  2. itsagixa

    itsagixa New Member

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    The tune wouldn't and shouldn't affect any component of the AC with the exception that a mafless tune MAY lower the vacuum needed to operate the different zones correctly
     
  3. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Thanks for the reply.
    Everything else is fine. Vacuum, Heater, fans, zones all good. Just the damn A/C wont switch on.
    Took it to holden a while ago and they said they tested everything. They put it down to the tune.
    I didn't think a custom chip would have anything to do with the A/C. I would have thought it was a completely different section of the PCM.
    I dunno, I now live about 2 hours drive from were I got the mods done and its hard for me to get back there. The guy who did it has been scratching his head too.
    It's really frustrating and doing my head in.
    I'm open to all suggestions, regardless how silly they may seem.
     
  4. immortality

    immortality Donating Member

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    It really depends what has been altered to go to MAFless. Unfortunately i'm not familiar with the VT tunes so not of much help. There would be heaps of settings in the tune in relation to the A/C and unfortunately the only way to see what has been altered would be to compare your tune to the factory standard tune.

    Ideally, you would need to hook the car up to a laptop and use something like EFIlive to see what is going on when the A/C is switched on so you can see what flags are been switched on in the tune and if anything is then switching it off.

    Ok, just had a quick look, the boys @ Delcohack do have software and definition files to suit the VT 195i engine. Best bet would be download Tunerpro RT, download the definition and tune files, get yourself a data cable an hook it up to see what is going on. All that you need can be found on the Delcohack website. The only issue that may crop up is that the tune has been altered to go MAFless and we don't know what has been changed to do so. Who ever made the changes to the BIN file (the actual tune) may have used some of the (programming code) space in the tune for the A/C system to put in code to go MAFless.

    The boys at Delcohack are very knowledgeable, check out the forum here delcohacking.net • Index page

    Edit: I've just had a quick look through the VT 195i tune. It doesn't look like a lot of the stuff has been defined (as most likely nobody has had any use for it). Ideally if you could find out who did the tune and what tuning software was used it would be a good start to figure out what exactly has been done.
     
    Last edited: Jan 5, 2013
  5. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Thankyou so much for all the infomation. This gives me a good starting point. I will pass this on to Scott and see what he comes up with.
    He is going to send me up a factory chip. So when I get that, it should confirm if it is in the tune.
    Thanks again.
     
  6. immortality

    immortality Donating Member

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    When the tune was converted to MAFless was any wiring changed? If you still have the MAF it would certainly answer the question.

    I'm not anywhere as good as the guys at Delcohack when it comes to doing code and shit like that. If you post on there forum someone may help you out and define the stuff you need in the XDF you need to see what is going on.

    I wouldn't mind seeing your tune though. Let us know how you get on.

    Cheers
     
  7. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    No wiring was changed as far as I know. The maf was removed and the plug taped up.
    I still have the maf at home. As a desparate attempt, I pluged the maf back in, but didn't work as I thought that if the maf program was removed,
    it wouldn't make any difference if it was there or not.

    I will keep this thread updated.
    Thanks again.
     
  8. Cheap6

    Cheap6 New Member

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    If I read the OP correctly, the A/C has never been seen to work?

    Maybe check if the PCM is (trying to) switching the A/C compressor. One of the two pins on the A/C compressor relay switching side should have power to it, the other is switched to earth via the PCM if the BCM sends a serial data signal to the PCM. Have you checked to see if the Voltage on the earth pin at the relay drops to zero when the A/C button is pressed? I have the wire as light green with a blue trace, going to F4 at the PCM. You can lift the relay a little bit out of the socket pin to access the terminal without disabling the relay operation.

    The A/C button is only momentary so if you can see the A/C signal input via Tech 2 that would suggest the BCM is seeing that as an input. Without climate control (SS - ???) the LED on the A/C switch should light via the BCM if the A/C signal is on. Is it?

    There should be Voltage at BCM terminal B3, dark green/yellow trace, as the blower fan input to the BCM. (No climate control.)



    What signal Voltage did you get out of the A/C pressure transducer? (I know it was "checked").
     
  9. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Thankyou for your reply, much appreciated.
    Yes, without climate control.
    In answer to your first paragraph, The result was.... With the relay removed, across the terminals that power the relay, there is 12 volts regardless of the position of the A/C switch. When the relay was connected, the voltage dropped to zero, also regardless of the switch position. This indicates to me that there is little or no current to fire the relay. Am I correct in saying this?
    Votage and current is good from the positve side of the relay socket, as the compressor clutch engages when the relay socket is bridged.
    I checked the wire between the relay and the PCM for continuity and all is good there. (It's actually XB. Light Green with a Black trace on my car).
    The A/C light does not come on at all.
    Holden said they checked the wire fom the A/C switch to the BCM terminal C9 and all was ok there.
    I will check the voltage at the BCM, terminal B3 and let you know.
    As far as the voltage out of the pressure transducer, I don't know. That was checked by Holden. I will double check.
     
  10. itsagixa

    itsagixa New Member

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    There may be a ground fault somewhere in the circuit however the fault may lie within the BCM, the easiest way would be to re-wire the circuit and run the relay wires straight to the AC switch...
     
  11. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Thankyou for your reply.
    I thought about the BCM as the fault.
    The A/C switch is positively powered and the relay relies on a negative signal from the PCM to fire it, as there is a contant +12 volts at the realy.
    I'm not too keen in by passing the BCM and the PCM as the fans wouldn't come on and the idle would not ajust. Also the pressure switch would be disabled.
     
  12. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    THANKYOU EVERYONE FOR YOUR REPLIES AND SUGGESTIONS. IT IS GREATLY APPRECIATED.

    I also want to check the data link wire between the BCM and the PCM.
    I think I found the colour of the wire but would like to confirm it.....Tan with a Black trace. Am I correct?

    Edit- Due to it being in the low 40's all this week where I live, there might be a little delay in doing these task. As I'm not as young as I used to be. lol.
    Edit II- To the Moderators.
    I only started this thread on the Mace section, as I thought they might know something as they do custom tunes (No offence to the guys at Mace).
    My appologies if it is in the wrong section.

    Geoff.
     
    Last edited: Jan 6, 2013
  13. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    I was reading through the manual and it said that when the A/C is switched on, the pcm delays the engagement of clutch on the compressor for a couple of seconds so as the iac valve can compensate for the extra load on the engine. Now, if the iac was faulty and couldn't adjust the idle, would the a/c switch on?
    I have been having trouble with the idle. On a cold start the idle doesn't increase. On a hot start, the engine will rev to about 1500 rpm for a few seconds and then drop to normal revs and when pulling up to a stop, with clutch in, the idle will increase also to about 1500 rpm for a few seconds, then reduce to normal.
    It's a manual, by the way.
    Food for thought.......
     
  14. Cheap6

    Cheap6 New Member

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    I can check the wire colour and terminal connections for the serial data between the BCM and PCM for you when I have access to a wiring diagram.

    I can't see any reason for the A/C not to work just because the IAC motor or valve isn't holding the idle steady. It's been too long since I've driven a VT 304 manual to recall whether it is normal to flare on a hot start but the flare coming to a stop doesn't sound right. Maybe that has something to do with the MAFless operation.

    If the A/C LED isn't lit then it's likely the BCM isn't sending a signal to the PCM to switch the A/C on either; the BCM switches the LED.

    It's easy to get lost looking for obscure things when there's a few electronic control units involved. In my experience the most common cause of A/C systems ceasing to work is the refrigerant leaking away which is why I was asking about the pressure switch Voltage signal output. It will be possible to provide a dummy 0-5V signal in place of that, as a test, and I can give you the wires and terminal assignations with the serial data terminals and wires (^) if you want.
     
  15. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Thankyou very much.
    I would be very grateful for any infomation you can give me.
    I will check that voltage at the pressure switch and let you know.
    As far as I know, the gas pressure is ok as it was re gassed and new compressor in Feb las year and Holden checked the gas pressure about 6 months ago.
     
  16. MACE

    MACE Active Member

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    No need to apologies Kracker,

    Interesting, technical, constructive threads are always welcomed here, as long as they're not derogatory

    I'm more spewing that have been slow to respond, but fortunately you've been given some solid advice :)

    Assuming that the hardware is all 100% in order then it would be a calibration/tune related issue which is certainly possible

    Am interested to see your findings

    Must plow through more work till everyone comes back on break :(



    Can't wait to see what the outcome is
     
  17. Cheap6

    Cheap6 New Member

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    Across those two terminals it should be 0V. With the relay in place, with respect to earth, there should be battery Voltage on both terminals unless the PCM is trying to switch the relay (and the A/C compressor) on in which case there should be 0V on the earthed side of the relay wrt earth. If the PCM is earthing the switching side of the relay then all the other components - A/C request input (the switch), BCM, pressure switch, refrigerant etc. and the connections between them - "upstream" have to be OK also.

    If you earth that wire - at the relay is OK if you know the connection to the PCM is good - with the relay in place, in parallel with the PCM earth, then the compressor clutch should likewise engage.

    As that's switched by the BCM also, if the A/C is 'on', that indicates to me that the BCM isn't going to be telling the PCM to switch the A/C on.

    D9 at the BCM? Red, white trace. It may depend on the BCM though.

    By way of explanation: B3 at the BCM is from the fan speed control so the BCM "knows" the HVAC fan is on.

    Wires:

    Earth: F16 at PCM, black.

    Pressure signal: B3 at PCM, green, black trace.

    5V reference: B7 at PCM, violet, white trace.

    I have the serial data connection between the BCM and PCM as red with black trace between D2 at the BCM and A3 at the PCM.

    Other thoughts:

    It's possible the idle flaring is the PCM correcting for an A/C compressor load on the engine that isn't there i.e. the PCM is earthing the A/C relay but there's a fault on that circuit somewhere. i.e. it's a symptom not a cause. That doesn't explain the A/C light not being lit though.

    There is a wide open throttle cut out of the A/C via the PCM. Something there?

    The BCM has to earth the blower inhibit relay via BCM B1, green wire, for there to be an input to the A/C blower input at BCM B3.

    There has to be a thermostat input at BCM D4, green wire, for the A/C to be on.

    BCM D9, red, white trace, is the A/C switch input (as ^).

    BCM B8, red, brown trace, is the A/C LED earth.

    The PCM switches off the A/C with refrigerant pressure too low or too high or coolant temp. too high.
     
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  18. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    WOW Cheap6 Thanks so much for the info. I really appreciate this.
    You certainly have been busy. You have given me plenty to work with.
    I should be getting that factory tuned chip in the next day or so. At least if that doesn't change anything, then at least
    I will know it's not in the tune. If it is the problem, well it's something they will have to sort out.
    The more I think about this, the more I'm thinking it's the BCM. After all, after the switch, the next thing that should happen is the A/C light should come on to show that the signal is being received by the BCM. So if the BCM isn't switching, then nothing after that would happen. Is my assumtion right??
     
  19. Nut Kracker

    Nut Kracker (Nucifrangibulum)

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    Update.
    Waiting on Scott from Chip Control to send me a "standard tune" chip to see if it fixes the problem.
    He did send me one the other day but the car would not turn over. He thinks maybe the security protocols were engaged not allowing a start up.
    Anyway....just have to wait and see.
    By the time I get this fixed, I will have to get a new compressor 'cause the seals will have dried out.
     
  20. MACE

    MACE Active Member

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    Scotty is a bit of a hard person to get a hold of these days, hopefully it get sorted before the seals in the compressor dry out
     

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