Bypass resistor

Discussion in '1955-1959' started by dorcutt, Dec 30, 2018.

  1. dorcutt

    dorcutt Member

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    The electrics on this new truck I picked up has been a friggen challenge. I have found a number of wiring errors and my lattest is the bypass resistor. It dose not seem that resistor is bypassed when you turn the switch to the crank position. I found a pink wire on the IGN 2 lug that went to the temp gage and it’s only hot when the switch is in the spring loaded crank position. I’m fairly certain this is incorrect. There is no green wire running from the ignition switch to the resistor. I have the brown wire running from the IGN 1 lug to the resistor and the other side (green wire) going to the coil.
    My question is the bypass necessary? I have read all the threads on the bypass logic and think I understand it.
    The truck has an automatic in it and standard points right now. I will probably throw a pertronics ignition in it in the future. The ignition switch is three position. Off On and crank which is spring loaded.

    Oh and thanks for all the help you guys have given me, it has been invaluable. The project is getting there.

    Oh ya Happy new year
     
  2. Bill Hanlon

    Bill Hanlon Member

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    The bypass is not absolutely necessary, but will make starting much happier, especially when cold or when the truck has not been started in a long time.

    Do you have a wiring diagram or has the wiring been done piecemeal?

    You are correct about the pink wire going from IGN2 to the temp gauge. The temp gauge should be powered from a common point that is fed from IGN1.

    There are two ways to feed 12 volts to the coil when the switch is in the start position assuming you have a solenoid (not stomp) starter.
    1. Run a wire from the IGN2 post to the coil + post.
    2. Most solenoids have 4 connections. 2 of them are physically smaller. One of these 2 smaller connections has a wire that goes back to the ignition switch's start position (IGN2). Run a wire from the other small solenoid post to the coil + post.

    Or instead of the coil + post, you could run the wire from either solution 1 or 2 above to the end of the resistor that has the green wire attached instead of to coil +.


    By the way, all this assumes that the engine turns over when you turn the key to the start position with current wiring. If not, let me know.
     
    Last edited: Dec 30, 2018
  3. dorcutt

    dorcutt Member

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    Thanks for the response Bill. You have confirmed the way I wired it, the pink to the IGN 1 post. I do have some wiring diagrams but not all seem to be accurate. The harness is from our host and I have the diagram for it but it appears to have been modified. Not show in some of the diagrams is how the flasher is wired not could I find a good diagram for the connections on the fuse panel. I have one buss that has a red wire from the light switch ( pwr) feeding the greywire that goes back to the light switch and a purple wire that feeds the flasher.
    I have the main buss tied to the ACC on the ignition switch which feeds turn all the fuse’s for the acessorys

    I believe my ignition switch is bad as it has four positions. Off,On,Start,and run which is spring loaded. The only continuity I get is in the start position between the BATT post and IGN 1 and ACC lug. When I go to the run position I loose that continuity but get it between BATT position the S lug and the IGN 2 lug. Everything is open in the off and on position.
    As far as the resistor goes I may wire it between the IGN 2 lug and the bottom end of the resistor or I may put the pertonics in.

    Not sure I’m correct yet. Let me know. Thanks. Dave
     
  4. Bill Hanlon

    Bill Hanlon Member

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    My '57 half ton was a GMC and is close, but not identical, to your Chevy. As far as I know, the only difference were the turn signal indicators in the dash. I don't know if the color scheme is the same between Chevy and GMC.

    Here is a link to a GMC wiring diagram: 1955 - 1959 GMC Trucks Maintenance Manual - Models 100 - 500

    I don't think original ignition switches were marked IGN1 and IGN2, but I believe IGN1 would correspond to IGN and IGN2 would correspond to SOL on the wiring diagram I linked to. Funny thing is I remember my '57 (RIP, it was totaled over 6 years ago) as having a separate ACC position on the key switch, but the diagram I linked to does not show one.

    Are your continuity readings of the ignition switch with no wires attached?

    With no wires attached:

    With the key in the OFF position there should be no continuity between any terminals.

    With the key in the spring loaded START position there should be continuity between BATT and IGN2. No other continuity.

    Release the key from the spring loaded position and there should be continuity between BATT, IGN1 and ACC.

    Turn the key to the one other position and you should have continuity between BATT and ACC. No other continuity. You may call this "ON", I'd call it Accessory.

    The GMC wiring diagram shows PINK for the wire between SOL (IGN2) and the S terminal on the Solenoid, same as your Chevy. It also shows a light green wire as the "bypass" connecting from the R terminal on the solenoid to coil+ terminal.
     
  5. dorcutt

    dorcutt Member

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    Many thanks Bill, The GMC schematic is closer to what I have then the Chevy diagram. Either way I can make it work.
    The continuity check was without wires leading me to believe I have bad ignition switch. It will go on my list of things to get.
    Thanks again.
     
  6. Bill Hanlon

    Bill Hanlon Member

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  7. dorcutt

    dorcutt Member

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    Thanks Bill. I took it apart per your suggestion and the contacts burnt and pitted and broken. Not salvageable. Have placed my order.
     
  8. vwnate1

    vwnate1 Member

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    I hope you ordered in the Pertronix Ignitor.....

    I missed where you said if it's a solenoid or foot pedal starter, the foot pedal starters don't use/need the by pass resistors .
     
  9. dorcutt

    dorcutt Member

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    Solenoid. No foot starter.
     
  10. vwnate1

    vwnate1 Member

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    Well ;

    In Vermont (where I spent time in the late 1950's & early 1960's) it's a maybe thing, for a V8 I guess....

    Me, I'd junk the contact points ASAP and slap in any sort of breakerless ignition, you DO NOT NEED FANCY-SCHMANCY ! I know the kiddies love those MSR and other brands but in reality those 1" long sparks have zero to do with making your engine run any better and everything to do with emptying out your wallet too often for replacement caps, rotor buttons, wires and spark plugs .

    All you need is : anything to take the load off the contact points as this will drive the stock, reliable ignition system to it's full out put, all the time cold or hot, fast or slow, July or January, those times when starting is marginal .

    See what I mean ? .

    Once you try a breakerless system you'll either be convinced or you don't have the feel .

    I've been experimenting with $35 Chinese rips offs of Pertronix on my vintage British cars for some years now and not a single failure yet .

    Pertronix used to sell for under $50, once they became popular they goosed the price to $125 overnight, I don't know how much they charge to - day but their big appeal to me is : fits stock distributors and NO modifications necessary .

    If you chose that route, try to get one that doesn't need the bypass system, if your truck is still original the ignition wire goes to the solenoid and thence to the coil, the wire from the ignition switch is a calibrated resistance wire, the wire from the starter mounted solenoid iw regular wire, in this way the coil's voltage is reduced unless the starter is actually operating, very simple and direct .

    ? are you old ? remember all those American cars from the 1960's & 1970's that always seemed to burn up the points in a few months ? most of them had replaced the ignition switch or the plug on the back and so had snipped off 1/4" or less of that calibrates resistance wire (purple in Ford products, cloth covered in GM's) forcing more than 7 VDC to the coil and points....

    All you needs to is choose the non by pass unit then TEST THE COIL TO ENSURE THE PRIMARY RESISTANCE IS THE CORRECT SPECIFIED VALUE and it'll work beyond your dreams and never fail unless you leave the key on with the engine stopped ~ that's the # 1 or #2 killer of these systems ~ either failure to test the coil and change as necessary or leaving the key on whilst doing other woks, or to listen to the radio (why OEM's added accessory positions) , allowing the system to be energized but never cycle ~ this is clearly outside the design parameters .

    Too many just shrug and think ' the coil's fine, it was before' and don't grasp the importance if getting a correct match .

    Remember of course to open those spark plugs up to .040" the instant you get rid of the breaker points ! .

    Oops, too long a post here I guess, I hope you're happy with whatever route you choose . enjoy the maple syrup, I see that most of it that I find these days, actually comes from Canada, I remember sapping in the early mornings as a child, freezing my butt off but having fun and sucking on the frozen chips of sap floating on the buckets .


     
  11. dorcutt

    dorcutt Member

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    Thanks Nate. I am somewhat of an old guy, I remember points, plugs, distributor cap well.
    I run the pertroinics on my 51 and have been pleased with it. I’ll do the same with the 57 except it’s lower in the priority list right now.
    Where would I find the resistance value for the primary coil?

    Dave
     
  12. vwnate1

    vwnate1 Member

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    Get out your ancient VOM and replace the battery in it, or go to Harbor Freight etc. and drop $5 on the cheapo ANALOG (means, meter, not digital) meter that fits in your hand and use it across the two small terminals ~ 1.6 (+/-) Ohms is for 6 volts, 3 Ohms is for 12 .

    ? I'm not clear on what you want to do on the '57......
     
  13. dorcutt

    dorcutt Member

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    Thanks Nate, I do have an anolog meter. Will confirm the resistance.
    I bought the truck but it wasn’t running although paper work confirmed the engine was rebuilt from a proffesional engine shop and a installed a TH 350 transmission.
    Since I’ve got it I have found a number of small issues, starter, wiring, radiator, heater etc. I am tackling them one by one. The previous owner was in the process of putting it back together after a frame off restoration but couldn’t finish it. As you have said several times it all about the journey. Well I’m living it right now and enjoying it.
    Thanks again for the help.
     

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