Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: Key On + Engine Off = Alternator Whine?!

  1. #1

    Key On + Engine Off = Alternator Whine?!

    Well the title pretty much says it all. When the key is in the "run" position but the engine is off the alternator makes a fairly high pitch whine. Well at least I think its the alternator, I poked around and even used a stethoscope and when I put it on the alt the sound became very loud and clear. So... this obvisouly isnt normal. BUT, if youve read my other posts, you would have noticed that my engine has ran like crap ever since I changed the plugs/wires, so bad that its not driveable (idles, starts, revs in neutral fine but no power at all)... I removed the alt when I changed the plugs/wires so I could access the rear bank easier. So... could I have messed something with the alt or wiring that would cause it to whine and the engine to not have any power (note: engine ran strong before plug/wire change/alt removal) ?? BTW while running the alt charges normal.

    Help! Ive had the car for 2 months and drove it only for 1 week. I need this thing to run before snowfall. ECM shows no stored codes. All the obvious has been checked. 90 beretta GT 3.1

    thanks!
    -john
    1991 Grand Prix GTP LX9swap/Getrag 284 --- SOLD =(
    1994 Corvette
    LT1/ZF6
    2006 Dodge Dakota 4x4
    3.7/42RLE

  2. # ADS
    Circuit advertisement
    Join Date
    Always
    Posts
    Many
     

  3. #2
    try unplugging the alt, and turn the key on (leave the battery connected, just pop out the electrical plug). See if it makes the noise. You might have a short in the alt.
    Taylor
    1988 Olds Cutlass Supreme 3100 MPFI
    1990 Pontiac Grand Prix STE 3.1 MPFI
    1994 Olds Cutlass Supreme convertible
    1998 Lincoln Mark VIII
    "find something simple and complicate it"


  4. #3
    Iron Head Enthusiast geoffinbc's Avatar
    Join Date
    Oct 2003
    Location
    Surrey, BC, Canada
    Posts
    5,770
    I'd say the rectifer is 1/3 or 2/3 dead. Pull the clip in plug see if the noise goes away. If it does you need a new alt. I had the same thing happen on my Sonoma
    1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
    1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
    Because... I am, CANADIAN

  5. #4
    but either of those possible causes wouldnt be cause for the enormous lack of power?

    update: went to car and removed harness. high pitched sound is gone. any ideas?


    thanks for the responses,
    -john
    1991 Grand Prix GTP LX9swap/Getrag 284 --- SOLD =(
    1994 Corvette
    LT1/ZF6
    2006 Dodge Dakota 4x4
    3.7/42RLE

  6. #5
    for lack of power, make sure that you do not have any spark plug wires crossed (I tend to do that ). Also, check your DIS and make sure that none of the coils are cracked (happened to me also). Make sure that you are not using any spark plugs made by bosch.

    I also recommend replacing the alternator.

    Plugged in = noise.
    Unplugged = no noise.
    solution = BAD (or getting that way) alt.
    Taylor
    1988 Olds Cutlass Supreme 3100 MPFI
    1990 Pontiac Grand Prix STE 3.1 MPFI
    1994 Olds Cutlass Supreme convertible
    1998 Lincoln Mark VIII
    "find something simple and complicate it"


  7. #6
    Quote Originally Posted by 3100 MPFI
    for lack of power, make sure that you do not have any spark plug wires crossed (I tend to do that ). Also, check your DIS and make sure that none of the coils are cracked (happened to me also). Make sure that you are not using any spark plugs made by bosch.

    I also recommend replacing the alternator.

    Plugged in = noise.
    Unplugged = no noise.
    solution = BAD (or getting that way) alt.
    Ive checked and rechecked spark plug wire routing so many times I've lost count. Plugs are rapid fire 6s gapped properly. I've tried 3 different ignition modules (each with 3 diff coil packs on them), currently the known good module and coil packs (taken from my running dohc) are in the 3.1 and the 3.1 module and coils in the dohc (and the dohc runs fine with them). I'm going to run the car for a minute with the accessory belt off to make sure that the alt isnt somehow creating an electrical problem causing my huge loss in power. Otherwise I'm at a loss on whats causing it

    thanks again,
    -john
    1991 Grand Prix GTP LX9swap/Getrag 284 --- SOLD =(
    1994 Corvette
    LT1/ZF6
    2006 Dodge Dakota 4x4
    3.7/42RLE

  8. #7
    Iron Head Enthusiast geoffinbc's Avatar
    Join Date
    Oct 2003
    Location
    Surrey, BC, Canada
    Posts
    5,770
    You are having drivability problems because the alternator has a bad rectifier and it it now puting out AC voltage and alot less current than it is suposed to be. You will still be getting 14V but it is not capable of putting out the current it needs to be.

    Change your alternator or find the same model from any vehicle and change the rectifier. Takes 20mins I did it to my truck. Took the guts from a 1995 Camaro alt left over from my swap and put it in the case for my truck.

    When my alt was like yours I also had a slightly goofy idle and flickering lights at low idle.
    1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
    1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
    Because... I am, CANADIAN

  9. #8
    Quote Originally Posted by betterthanyou
    You are having drivability problems because the alternator has a bad rectifier and it it now puting out AC voltage and alot less current than it is suposed to be. You will still be getting 14V but it is not capable of putting out the current it needs to be.

    Change your alternator or find the same model from any vehicle and change the rectifier. Takes 20mins I did it to my truck. Took the guts from a 1995 Camaro alt left over from my swap and put it in the case for my truck.

    When my alt was like yours I also had a slightly goofy idle and flickering lights at low idle.
    Sounds like a possibility... but I have run my dohc with no accessory belt (which means no alt) for minute (on a test run down the driveway) and it had all its power. I ran the 3.1 (on a battery that had been charged overnight) with the harness unplugged and serpentine belt off and still no power. Althought the alt does seem bad (from the sound) I can't justify replacing it until the engine runs right... this is of course assuming that the alt isnt the cause of the problem in the first place, which I dont truely believe it is
    1991 Grand Prix GTP LX9swap/Getrag 284 --- SOLD =(
    1994 Corvette
    LT1/ZF6
    2006 Dodge Dakota 4x4
    3.7/42RLE

  10. #9
    Anonymous
    Guest
    Go buy a new alt, replace it, see if thats the problem. If not, return it. I would that at this point you'd be willing to try anything.

  11. #10
    Iron Head Enthusiast geoffinbc's Avatar
    Join Date
    Oct 2003
    Location
    Surrey, BC, Canada
    Posts
    5,770
    If it is whining the rectifier is bad. Take a look at it. Remove the little plastic cover that covers the soldered connection between the rectifier and the case windings. Do you see any heat marks? It will look like white gray or black poweder sitting on the rectifier, wires or case. This will be a sure sighn the rectifier is toast. It could also have burned up a diode internaly and there will be no sighn of heat.

    Do another test hook up a multimeter and test for AC voltage. See what happens.
    1993 EXT. CAB, 3.4L V6 TBI, 5spd manual. Sonoma
    1990 4Door, 3.2L V6 TBI, 5spd manual. 4X4. Trooper
    Because... I am, CANADIAN

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •