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ballast resistor

Discussion in '40- & 55-Series Tech' started by johnny, Mar 26, 2003.

  1. johnny

    johnny

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    this may make me look dumb but i don't care. i'm still having trouble with my ride, haven't had time to work on it. anyway i got around to checkin out the ballast resister and the problem is, i can't find one. now, i'm running classic point ignition so i must have them right? i looked in the spector cataloge, to make sure, and found a picture of 2 different ones and neither of them are in my cruiser. all i have that is near the coil is cylinder with a wire commin aout of each end. any help??
     
  2. Sparky_Mark

    Sparky_Mark

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    I suspect what you have found is the "condensor". This is really just an electrolytic capacitor. By the way, my truck runs fine without it, but I know I need to replace it very soon. It goes from the Coil + terminal to GND. I think these show up on '78 and up trucks (my '79 has one). Check your schematic, or look at the one in the Tech Links that Jason Peters has posted.

    By the way, does anyone know what the value of this device is (in microfarads, not price)? Please don't guess, if you write "I think", I will ask you to justify your answer with the analysis of the RLC circuit. I can get parts, I just want to make sure I'm getting the right value.

    The resistor would be hard to miss, it's a large white ceramic block. It's not absolutely necessary, but you will eventually burn your points out if you don't have it in the circuit. You can see if your truck runs if you tie the IGN feed directly to the coil + terminal (the starter solenoid sends full voltage to the coil for crank only). If it runs, disconnect it and go get the resistor (resist the temptation to run you truck like this - you'll be sorry). If you don't have a digital multimeter, now might be a good time to get one. There are lots of things that could give you trouble.


    ...I hope this helps
     
  3. johnny

    johnny

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    no i know what the condesor is, and the thing i'm talking about isn't it. i have nothing that links the +/- and coil. maybe i should go get one. ha
     
  4. Erics75

    Erics75

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    Hi Johnny and Mark, your right about the condensor being a capacitor, but it doesn't have anything to do with an RLC circuit. DC only has resistance in the circiut, while AC can have Resistance (R), Inductance (L), and Capacitance (C). By not having a condesor you will pit/burn your points, the condensor temporarily gives the current a place to flow, thus preventing an arc between the points when opening.As for not having a resistor, the coil will burn up ( not including HEI systems ). Johnny's description of the cylinder with a wire on each end is probably the resistor. Most condensors have a ring connector that screws to the distribtor and 1 wire coming out of one end. There may be numbers ( part number or a rating in microfarads or picofarads ) on the resistor that can be matched up to another one at an auto parts store. I'm not trying to disagree with you Mark or lecture on ignition systems just putting in my two cents.
     
  5. Gumby

    Gumby Supamod Staff Member s-Moderator

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    According to the F Engine factory manual for a 74 the capaciator is .20-.24 microFarads.

    It's been awile since I have had an F motor, but isn't the capacitor by the points and the thing off the coil for radio interference?
     
  6. Rocky_LC

    Rocky_LC

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    I have a '74 FJ-40 (F Engine) and my ballast resistor is actually mounted in a square metal housing right near the coil on the passenger side fender. It's mounted just below the coil, about 2" below it, on the back side of the coil mount.

    If you remove the box and look inside, it has a wire wound resistor on a ceramic core. It looked like a rusty sheet metal box, about 3" long, by 1" wide.

    Mine is easy to find by folllowing all the wires off the coil terminals.

    Hope this helps.

    Rocky
     
  7. Degnol

    Degnol

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    A resistor simply lowers the current through it. A capacitor stores current for discharge. The intended purpose of the ballast resistor is to cut down the voltage to 6-9 volts to the points. There are other resistors in your wire loom, like in the heater motor(s), to give you two speeds. In electronics shop, the fun thing to do was to charge up a capacitor and throw it to a guy and watch him get shocked when he caught it. It's like foil and waxed paper rolled together. Ben Franklin"s jar in which he stored electricity... it's where the lightning went. &nbsp:Don't know whether you have points or not, but suspect that you do. You need a ballast resistor. Some wire a lead to the down line (read bypass) on the resistor for starts, but running you have got to go through the resistor. I made it about 22 miles in an MGA W/O one and had to stop in Columbia, MO to get one.
    GL :)
    Ed
    Long