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Starter relay mod for dummies

Discussion in 'Electronics' started by MattC, Jan 22, 2017.

  1. MattC

    MattC Well-Known Member Donated!

    Let me start by saying that I am hopeless with all things electrical. Sure, I can join bits of wire to other bits of wire in the vague hope that when electricity is applied the bits of wire do what they're meant to do and don't catch fire, but how does it all happen? Blowed if I know.

    My car has been reluctant to start of late. Being an occasionally avid forum-goer I am aware that this problem is far from unusual, and that somebody much smarter than me figured out how to fix it a long time ago. The diagram generally issued as the solution, however, is hieroglyphics to an electrical Neanderthal such as myself:

    [​IMG]

    OK, so "12V" and "Ground" even I can figure out. Its the other two that my tiny little brain struggled with. "Ignition side of starter wire" - how the hell do I know where that is?? "Starter motor" - well clearly I know where the starter is, but which bit am I attaching a wire to??

    After much Googling and a painful amount of head-scratching I finally figured out which bits need to be connected to which other bits (I still don't understand the why's or the how's, but bear with me), and so I present to you, dear forum friends, The Starter Relay Mod, for Dummies

    Here are the bits you will need. From top to bottom, left to right: Electrical tape, in-line fuse holder with 30A fuse, wire strippers, a 30A 4-pin relay, female and male 6.4mm spade connectors, butt connectors/crimp connectors/splice connectors/whatever you call them, ring terminals, wire (thinner for the ignition wires, thicker for the power and ground), flat-nose pliers. Not pictured - beer.

    [​IMG]

    The first thing you need to do is work out where you're going to mount your relay. I bolted mine to the side of the fuse box basically right over the top of the starter, it makes for nice short cable runs and pleasing presentation. Which is almost as important as the actual operation of the device.

    Now, lets look at the starter. There are only two wires connected to it. The thicker of the two is bolted to the starter. Don't touch it. The other one is clipped to the starter with a brown plug. Your car may have a different colour plug. Mine is brown. It will therefore be referred to as "the brown plug" for the remainder of this post. Just substitute "brown" for "whatever colour your car has". Not too hard so far, right?

    [​IMG]

    Unplug the brown plug. Now you need to make up two new wires. You've got your relay dummy-mounted in it's intended location so you can measure how much wire you need to cut, right? One of your new wires is going to go from the brown plug to the terminal marked 86 on your relay, it should have a male spade connector on one end and a female on the other end. The second cable will probably need to be a little longer, will have female spade connectors on both ends, and will go from where the brown plug used to plug into the starter to the terminal marked 30 on your relay.

    [​IMG]

    Time to make your power wire. Your in-line fuse connector likely came with a single piece of wire connecting both sides. Clip this somewhere in the middle. Now put a female spade connector on one end. Work out how much extra power wire you need to reach the positive battery terminal and add that using a butt connector/splice connector or what have you. Put a ring terminal on that end. I'll fess up here to goofing and buying a butt connector that wasn't wide enough to take the gauge of power wire that I bought, so since I couldn't be bothered going back to the electrical supply store for different connectors, I twisted and soldered the wires together then taped them up.

    [​IMG]

    Now make your ground wire. As above - female spade connector on one end, ring terminal on the other.

    [​IMG]

    The ground wire needs to be bolted to the chassis. I used this convenient threaded hole on the inner guard next to the air intake:

    [​IMG]

    Time to plug it all together - power cable to terminal 87 on the relay, ground cable to terminal 85, brown plug to terminal 86, wire plugged in to starter where brown plug use to go to terminal 30.

    It should look something like this:

    [​IMG]

    [​IMG]

    Start car. Rejoice. Drink beer.
     
    Rick89GTS and lone wolf like this.
  2. Rick89GTS

    Rick89GTS Well-Known Member Moderator Donated!

    Hi Matt, kudos for an excellent write-up. That diagram has been around for a long time but thank you for documenting the step-by-step process. Well done!
     
  3. MattC

    MattC Well-Known Member Donated!

    Thanks Rick, I'm pretty sure I pinched the wiring diagram from one of your threads :D

    Oh and btw for anyone reading this, when you're making up the 4 leads as described above, make sure you solder the spade connectors and ring terminals to the wires. If you just crimp them on, they may vibrate their way loose, and then you're back to having a car that won't start. Ask me how I know that :mad:
     
  4. Rick89GTS

    Rick89GTS Well-Known Member Moderator Donated!

    No worries, all good. We're all here to help each other out! :cool:
    I bolted my relay top the inner fender wall, so I have longer wires.
     
  5. KelbonHD

    KelbonHD New Member

    Hey so I did this mod and my car started up perfect for about a month and a half but now it doesn't want to start again, and I am completely stumped. I checked all the wires to make sure they were still good to go and had a proper connection, the battery seems to be giving proper power, the alternator I'm sure isn't the problem otherwise my battery wouldn't have a good enough charge right now, and I think there just isn't any power getting to where the brown plug is supposed to go. I have no clue why, and I don't see why the starter would just randomly stop working if that was the case. Everything involved with the start relay mod is perfectly fine, and I've even taken the time to remake some of the wiring. Any help would be appreciated.
     
  6. MattC

    MattC Well-Known Member Donated!

    Check all of your spade and ring connectors are actually still connected to the wires. Per my follow-up post above, I had the same thing happen to me and it was a spade connector that I had crimped instead of soldering which had worked its way loose. If that all checks out, you've either got a bad ground, a blown fuse, or a faulty relay. I'd check them in that order (cheapest to most expensive fix :D)
     

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