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Fan Kills Engine

Discussion in 'VN - VP Holden Commodore (1988 - 1993)' started by 88GreenVN, Jul 26, 2006.

  1. 88GreenVN

    88GreenVN Next Exit Left

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    I have made a graph of the data from Winaldl when the car engine quit.

    It looks like the fan relay droped the voltage and the engine stoped. I roll to a stop. Slip it out of drive hit the starter - engine starts and off we go.

    Can the drop in voltage kill the engine?
     
    Last edited: Jan 3, 2009
  2. HDT_aero

    HDT_aero Banned

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    interesting does the fan still work??
     
  3. HDT_aero

    HDT_aero Banned

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    also was this a once off or is it a repeat offender
     
  4. 88GreenVN

    88GreenVN Next Exit Left

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    The fan still goes. Car has been stalling every week after the DFI fryed itself 3 months ago. I looked at the event data and the graph is the result.

    I have just replaced the relay and will go for more tests later tonight turning the a/c on and off to see if I can get it to do it again.
    Still have a ruff idle.
     
  5. mouce

    mouce Physics Geek

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    That's a strange one though, because it's on the second fan request that the voltage falls through the floor. I'd say that it's only part of a much larger problem.

    Have you tested the alternator? Because for a voltage drop to happen like that...it makes me think that the voltage regulator is having issues. Just a thought.
     
  6. 88GreenVN

    88GreenVN Next Exit Left

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    New alt about 3 years ago. but yes thinking its the alternator.
     
  7. mouce

    mouce Physics Geek

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    It would be nice to know just what did trigger the voltage dip like that though...because looking at it, when the fan relay switched it only dropped a bit (nothing too drastic), then all of a sudden the SECOND fan request killed the engine??? WTF?

    Is is possible that there's a strange earth leak, or even a short in the fan motor? That would create a voltage dip, although that should blow a fuse somewhere.

    Another possibility is that there IS something dodgy with the charging system, I know that when I grab my high-beams, the system voltage hits about 11V for a split second before the alternator can compensate for it (I love having the voltmeter in the cabin:)).

    Try placing as much 'instant' load on the electrical system as possible using something other than the fan...try your high-beams...they put more load on the system than the fan does (or at least they should). Also...just to be a little nastier, turn on the rear window demister too (that sucks a bit of juice). Test that out and see what happens.
     
  8. 88GreenVN

    88GreenVN Next Exit Left

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    On the chart the first fan call kills the engine. Revs hit 0. Car rolls to a stop (bus stop) slip into park and start the engine first kick.

    I've looked back over the 3 data sets I have recorded and when the volts hit 11 the engine stalls.

    I changed the fan relay and did the same drive test loop and the volts were stable. I turned the a/c on and off 20 times during the drive with no effect on the volts.

    The problem would appear to be the fan regulator, (replaced now) the fan itself or the alternator (new 2004).
    I'll do the same test loop tonight with the a/c, rear demister on and some high beam too boot.
     
  9. VN_Luke

    VN_Luke ƃuoɹʍ ʇsnɾ sı sıɥʇ

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    dodgy earth somewhere?

    fan relay is triggered by computer earthing a pin on the relay....?

    dfi module not earthed properly?
     
  10. 88GreenVN

    88GreenVN Next Exit Left

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    Dodgy earth? Well I've been over the car for the past 3 months looking for the stalling fault. I'm not saying its not a bad earth or connection (the oxy sensor connector was bad) I'm just hoping the relay was bad. I think I have tracked it to the fan system/alternator. The earth for the DFI is good, the earth by the battery is good. Is there any more earth points I should check?
     
  11. VN_Luke

    VN_Luke ƃuoɹʍ ʇsnɾ sı sıɥʇ

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    check all the ECU earths - there's about 4 or 5 black cables from the ECU, if you need pin numbers i can let you know by tomorrow....

    My theory (with limited electronics knowledge) on the dodgy earth is that the voltage is measured at the ECU.... maybe the ecu isn't earthed properly, and when something requiring earthing (like fan switching on) along with everything else that's being earthed by the ECU, it could mess things up? along with giving faulty voltage readings?

    Just a silly theory, but might be worthy trying, if you've been looking for 3 months! :p
     
  12. 88GreenVN

    88GreenVN Next Exit Left

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    I'll look at the earths on the ECU. I got the data cable a few days ago so now can see whats happening. But need to learn what all the numbers mean....
     
  13. 88GreenVN

    88GreenVN Next Exit Left

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    Spoke to a sparky today and he said to look at the anti theft bypass above the clove box as this could be the fault.
    Also some one said they had a crap running car and replaced the fuel pump and that fixed it. Can a dodgy wire connection to the fuel pump kill the engine? you can hear the pump when u turn the ignition on and off again. The engine starts instantly when u turn the key after it stalls every time. Very puzzled on this one.
     
  14. VN_Luke

    VN_Luke ƃuoɹʍ ʇsnɾ sı sıɥʇ

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    anti theft switch is an interesting theory....

    but i'm not sure if you have one on the vn?

    basically, the anti theft bypass switch will give your ecu +12v to pin A6 (or A5) can't remember, but it's one of those and it's a pink wire....

    when there is no +12v at that ecu pin, you get no injector pulse... (or the efi relay isn't triggered, or something like that :) either way, car will NOT run with anti theft pin not powered)

    Luke.
     
  15. VN_Luke

    VN_Luke ƃuoɹʍ ʇsnɾ sı sıɥʇ

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    is the ECU logging any error codes?
     
  16. 88GreenVN

    88GreenVN Next Exit Left

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    Well I just opened the glove box and touched the key for the anti theft lock and car dies..... poke a screw driver in it and give it a twist car starts. riggle some more car dies.
    This must be it. After 3 months of !!#@##*&^(*)^*&....theirs some new words it there!!! I feel better now.

    Must be a short or something like it. Ill try to bypass it (the vn sedan I have has a bypass not the wagon)
     
  17. 88GreenVN

    88GreenVN Next Exit Left

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    No error codes from the ecu. I've made peace with the fan...
     
  18. 14secvp

    14secvp New Member

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    That anti theft key is that whats in my door shut of my 92 vn then Ive never touched it wasnt keen in case it didnt go again. going to cut it out now for sure.
     

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