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

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

    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.

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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

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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.

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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 by immortality; 05-01-2013 at 11:27 AM.
    Body by Holden, Soul by Brock
    the Legend will live forever

    VN exec T5: 15.1sec @92.2mph 1/4 mile, 9.7sec @ 74.6mph 1/8mile, 2.3sec 60ft, 0-60mph 6.827sec 22/11/07 Gtech competition

    Quote Originally Posted by Reaper View Post
    Nope - back pressure is a complete fallacy. In short - do you fart any better with a cork up your arse???

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    Quote Originally Posted by immortality View Post
    It really depends what has been altered to get 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.
    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.

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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
    Body by Holden, Soul by Brock
    the Legend will live forever

    VN exec T5: 15.1sec @92.2mph 1/4 mile, 9.7sec @ 74.6mph 1/8mile, 2.3sec 60ft, 0-60mph 6.827sec 22/11/07 Gtech competition

    Quote Originally Posted by Reaper View Post
    Nope - back pressure is a complete fallacy. In short - do you fart any better with a cork up your arse???

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    Quote Originally Posted by immortality View Post
    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
    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.

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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").

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    Quote Originally Posted by Cheap6 View Post
    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").
    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.

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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...

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