Bad Ballast resistor?

Discussion in '40- & 55-Series Tech' started by Tigerstripe40, May 8, 2006.

  1. Tigerstripe40

    Tigerstripe40

    Messages:
    1,807
    Location:
    Utardia
    I was ahving a starting problem in Moab.

    Symptoms:
    Truck hard to start.
    Cranks fine, and 'catches' with the key in the 'Start' position.
    When the key is moved to 'On' truck does not continue to run.
    Was getting continually harder to start.
    Was filling up on gas on the way out of town, truck would start to run on it's own, but would not stay running.

    I bypassed the ballast resistor and ignitor.
    Truck started, and ran fine all the way home.

    I figure that this is the ballast resistor.
    What kind of resistance readings should I get out of a properly working ballast resistor?

    ALso, hwat is the appropriate process to test the ignitor?

    This is on a 1976 FJ40 with a non-USA points type distributor, and stock coil

    Thanks!
  2. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    How did you go about your 'bypass' the ballast resistor?

    A jumper wire from the positive on the battery to the positive on the coil?
  3. Tigerstripe40

    Tigerstripe40

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    Yeah.

    I completley disconnected the ignitor and the ballast resistor, then ran a jumper wire from the battery positive to the coil positive, and I also ran a jumper from the dizzy to the coil negative.
  4. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    So you removed the 'on' position on the igniton switch from the mix, along with the ballast resistor...


    I would ohm out your ignition switch......I have seen them fail, just as you are describing here.


    :beer:
  5. Tigerstripe40

    Tigerstripe40

    Messages:
    1,807
    Location:
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    I would have done more troubleshooting, but I needed to get on the road home to Salt Lake, and I didn't have a wiring diagram with me.

    So, to ohm out the ignition switch, do I test the switch for any resistance whatsoever??

    Thanks!
  6. Pin_Head

    Pin_Head

    Messages:
    11,693
    Location:
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    This is a classic sign of a bad (open or broken wire) ballast resistor. The ballast resistor is about 5-10 ohms IIRC, but if it fails there will be no conductivity. The reason that it starts in the start position is that some years have a bypass wire from the starter to the coil that is hot in the start position.

    If it is the switch, then you would expect that the other circuits that run off of the key on position (like the turn signals) would have problems too.
    Last edited: May 10, 2006
  7. Tigerstripe40

    Tigerstripe40

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    1,807
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    yeah, that's what I figured.
  8. Nomis

    Nomis

    Messages:
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    What harm, if any, would be caused by bypassing the ballast resistor indefinately? Too much juice to the coil would fry it eventually?
  9. Tigerstripe40

    Tigerstripe40

    Messages:
    1,807
    Location:
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    The ballast resistor is to keep the points (yes, I still have points) from burning out.
  10. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    There is NOTHING wrong with a points ignition system....they work very well and are very reliable.


    :beer:
  11. Tigerstripe40

    Tigerstripe40

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    Agreed

    :beer:

  12. Pin_Head

    Pin_Head

    Messages:
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    Location:
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    Actually the ballast is there to prevent the coil from overheating and burning out.

    The ballast helps with starting during cranking because of the voltage drop during cranking because of the high current demand from the starter.

    The solution is to use a coil that works at a lower voltage, but this means that it will overheat and burn out if run at the normal 14V.

    The solution to this is to run a bypass wire to the coil from the starter that is hot only during cranking to provide full batery voltage and then after the engine is running, use a ballast resistor to drop the voltage to what the coil needs during normal running.

    Some cruisers didn't use the ballast resistor and have a different coil. If you have a low voltage coil, you also need the ballast resistor.

    HTH
  13. Tigerstripe40

    Tigerstripe40

    Messages:
    1,807
    Location:
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    I think I need a little clarification here...

    I look up Ballast Resistor at the autoparts web sites, and this is the part I get.

    [​IMG]

    This looks like the part in black, with the red - and + on it below.

    However, what I think went bad is the piece in grey (which is a white ceramic piece, with 4 wires, and stinks of burnt electronics).

    This is hard wired to the ignitor, but it is removeable (after snipping the wires going into the ignitor)..

    It looks like a big resistor to me. IS this the ballast resistor, or is that part of the ignitor???
    ballast.JPG
  14. Pin_Head

    Pin_Head

    Messages:
    11,693
    Location:
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    I don't understand your diagram, but one end of the resistor connects to the black/yellow stripe ignition wire and th other end connects to the coil + post. The ignitor hot wire also connects the the black/yellow side and the bypass wire from the starter (black/white stripe) connects to the coil + side.

    Resistor are not polarized, so +/- doesn't make sense, but in the picture, the ring terminal provides the connection tot he coil+ post.

    It is not likely that your ignitor is burned because it runs fine when you bypass the resistor. You don't want to run it for long that way as it will overheat your coil.
    HTH
  15. Tigerstripe40

    Tigerstripe40

    Messages:
    1,807
    Location:
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    I completely disconnected the ignitor.

    Here is a better picture....

    The part circled in blue is the ignitor.
    The part circled in red, looks like the ballast resistor in the picture above, but I am unsure of what that is exactly.

    The grey ceramic piece in the drawing above is under the metal plate, and is circled in green in this pic. I thought TAHT was the ballast resistor.
    coil.jpg
  16. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    It is.


    Toyota put that little shield over it to keep you from burning yourself on it.


    :)
    Last edited: May 10, 2006
  17. Doug_S

    Doug_S

    Messages:
    880
    Location:
    Olympia, WA
    Since I no longer have an igniter just a non-USA dizzy along with a coil ignition system...that means I no longer have a ballast resistor???
  18. Pin_Head

    Pin_Head

    Messages:
    11,693
    Location:
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    It depends on the coil, not the ignitor. Resistor type coils need a resistor, but you also need the resistor bypass wire from the starter for reliable starts.
  19. Tigerstripe40

    Tigerstripe40

    Messages:
    1,807
    Location:
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    The ignition switch tests out fine.

    The ballast resistor tests out at 3-4 ohms.

    The mystery resistor, is actually 2 resistors in one package. One side tests at 24 ohms average (ranged from 23.8 - 24.3 ohms)on one side, and 12 ohms average (11.9-12.4 ohms)on the other side.
    The ceramic is printed 24 ohms on one side, 12 ohms on the other. I figure that was allright.

    So I think that I might have a problem with the ignitor.
    The truck will crank, and fire, but as soon as I move the key from 'Start' to 'On' the truck dies.

    How do I go about testing the ignitor?
    Or have I pretty much isolated the ignitor as being the problem?

    It might be bad wiring between the ignition switch and the coil..... :eek:
  20. Pin_Head

    Pin_Head

    Messages:
    11,693
    Location:
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    It can't be a bad ignitor if it runs fine when you how wire it.

    What is the voltage at the + side of the coil when the points are closed and the key is on (not running)? If it is low, it suggests that the wiring or connections are bad somewhere between the coil and switch.

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