Alternator light

JasonNC
JasonNC Expert Adviser
edited November -1 in HUDSON
I replaced the generator with an alternator when I switched over to twelve volts several years ago. Last week the alternator light came on and stayed on. I bought a new alternator and when I hooked the battery cable up, the idiot light came on and stays on until I turn on the ignition switch at which time the oil light comes on and the alternator light goes out. I think I have a short somewhere. Any ideas?

Comments

  • Park_W
    Park_W Senior Contributor
    Maybe the wires to terminals 1 and 2 on the alternator got swapped?
  • JasonNC
    JasonNC Expert Adviser
    Thanks Park, but I don't think that's the problem. I played with switching those wires and got the same result. In fact, I seem to have juice going from the battery back to the alternator. I put a test light to both 1 and 2 terminals and the (ground?) bolt on the side opposite the single wire that's connected to the solenoid and I have power on all three just by connecting the battery cable. If you touch 1 & 2 simultaneously, you get a nasty spark. I'm afraid to run it since it will probably burn up a new alternator.
  • GrimGreaser
    GrimGreaser Senior Contributor
    Here's a place to start:

    http://www.alternatorparts.com/repair_manuals/10si-15si-type-116-136-repair-manual-page-3.html
  • Clutchguy
    Clutchguy Senior Contributor
    What year is your car?, and I take it that it still has an original harness in it?. I have found that on most stepdown cars from 48-51, look at the wires that go underneath the cowl support on the drivers side. You have the oil sending unit wire, the ignition and the trigger wire for the gen. all go thru there. Just normal wear and tear causes the insulation to come off. They can touch the frame or other wires that have no insulation either. Of course, if it has a different wire harness, I haven't a clue. Good luck, CG

    DON"T TUG AND PULL ON THE WIRES AND CAUSE SOMETHING ELSE TO SHORT IF IT IS AN ORIGINAL HARNESS.
  • Club Coupe
    Club Coupe Expert Adviser
    edited December 2011
    This might be a long shot, but it happened to me once. Check to see if your fan belt is slipping due to it wearing on the pulley side and becoming slick. The only way that I know to check that is to try pulling on the belt, or simply just replace it. Also, another thought; if your alternator doesn't have the built in regulator, have you checked your voltage regulator?
  • Geoff
    Geoff Senior Contributor
    Okay, all you have done is change the alternator, right? So it has to be the alternator connections. However, I cannot understand why the dash light illuminates, and then goes out when you turn the key, as normally the voltage is provided from the keyswitch for this. You need to check out the alternator connections, and what they are connected to internally, and if they are the same as the old unit.
  • mars55
    mars55 Senior Contributor
    You did not say ehat kind of alternator you are using. Maybe you put on the wrong kind.
  • JasonNC
    JasonNC Expert Adviser
    mars55 wrote:
    You did not say ehat kind of alternator you are using. Maybe you put on the wrong kind.

    It was the same as the one I took off. It's the single wire alternator that was primarily used by Chevrolet. I'm just going to check all the wires since I created this wiring harness myself years ago.
  • Hudson Grandpa
    Hudson Grandpa Expert Adviser
    Did you make absolutely sure that you got a 6v Positive or Negative Alternator, as per your car requires. I have a one wire Alternator, that goes to the Bat terminal of the New Voltage Regulator. My car is Negative Ground. I think my Gen light burned out long ago. Have a 6 volt Optima Battery. No light doesn't bother me as long as I turn the key and it pops into rpm. No problem for over a year now.
    cold or hot weather.
  • [Deleted User]
    [Deleted User]
    Well I have been a servive tech my whole working life. Not on cars so much as industrial equipment. when something like this comes up the first thing I ask myself is " What did you do to cause this"
    You replace a known bad part (maybee) with a new part (possibly bad).
    You unhooked and as Clutch Guy said "Moved wires around"
    You either have a short of sone sort to ground or between wires or a bad or wrong part
    Roger
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