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Solenoids going bad

Discussion in 'Mechanic and Repair' started by Lasko's Lawn Service, Sep 26, 2012.

  1. Lasko's Lawn Service

    Lasko's Lawn Service LawnSite Member
    Posts: 183

    I have a 07 Scag TC that keeps burning up solenoids...I get 12 volts on the ignition wire coming into the solenoid and after unhooking the feed wire to starter I get 12 volts there as well. My local dealer said there is a diode in the ignition portion of the wiring. The wiring diagram also shows a diode coming off the relay there. I don't see it though. Could I be getting backfeed through a diode that might be actually in the relay or do I just need a good heavy duty car solenoid? Perplexed...
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Dear Perplexed....... Hehe

    There is no diode in the relay, Make sure the cable on the starter is clean and not rusted/corroded. Also clean and lube the starter to reduce possible excess drag, You can give a heavier duty solenoid a try as well but check the other things first......
  3. Lasko's Lawn Service

    Lasko's Lawn Service LawnSite Member
    Posts: 183

    Man it sure looks clean....the connection that is...the starter is brand new...the new solenoid will fire the engine right up...but over the course of a couple of weeks the clicking continues and the solenoid eventually goes bad.
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    If that's the case go to a heavier solenoid, Solenoids are 12 volts same as the battery so they shouldn't be going bad that quick.....


    How many times a day are you starting this machine ?
  5. Lasko's Lawn Service

    Lasko's Lawn Service LawnSite Member
    Posts: 183

    Well that's what I'm going to try...I start the thing probably 4-5 times a day...
  6. JimQ

    JimQ LawnSite Bronze Member
    Posts: 1,139

    Is it possible that the control voltage for the solenoid is low? It's possible to get a cumulative voltage drop in that circuit with all of the safety switches that it travels through.

  7. Lasko's Lawn Service

    Lasko's Lawn Service LawnSite Member
    Posts: 183

    Well I only get like 8-9 volts when I crank the engine on the ignition wire at the solenoid...but I figured that was the drop in voltage because of the draw from the starter...when I disconnect the starter feed and test there when I'm cranking the engine I get the full 12 volts...but I'm just not sure there should be that much fluctuation when I'm cranking...is 8-9 volts enough? I keep thinking no, but I'm no expert...maybe that's whats throwing the copper bar in the solenoid up and down?...
  8. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,253

    Here's what ya do bud.
    You wire in a standard cube type relay to fire the solenoid. Absolutely will cure what ails ya.

    Follow along: Remove the starter switch wire at the solenoid and connect it to terminal# 86. Wire term. # 87 to ground (this will activate the relay).
    Wire term. # 30 to the terminal on the solenoid that the heavy battery cable is attached to. Finally, wire term. # 87 to the solenoid terminal that you removed the starter switch wire from.

    Here's how it works: When you hit the key start switch, you send 12v to the cube relay coil. The contacts close and send 12v to the solenoid.
    You want to keep wires as short as possible. you can prolly just use a cable tie to secure the cube to the heavy bat. cable or any handy place.

    The cube relay terminals : 86 & 87 are the coil. 30 is common. 87 is N.O. 87A is N.C.
  9. BigFish

    BigFish LawnSite Gold Member
    Posts: 3,253

  10. hdtvluvr

    hdtvluvr LawnSite Senior Member
    Posts: 485

    Here's a link to a thread in a tractor forum that explains how to do it and contains photos and diagrams. I have the link saved so when I need it I can reference it.

    Hope it helps.

    Starter Assist Relay Assembly and Install

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