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Junior Charter Member
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131 Posts
Discussion Starter #1
Older style relay has two small posts do both need to be hot for starter to run? What is the corect hookup to use sixtys type relay with doner fi harness?
 

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Premium Member
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6,408 Posts
You will not be using the "I" small terminal...Only the "S" small terminal is used...
As you look down on the top of the relay , all the positive wires (except the "exciter" wire from the clutch switch) , go to the right hand large terminal....Only the starter wire goes to the left side large terminal(looking down on the top)...The "exciter wire (with the "L" shaped rubber end) hooks on the small "S" terminal.
The bracket is ground , and must have a good solid connection to the car's frame.
 

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Junior Charter Member
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131 Posts
Discussion Starter #4
I have tried start wire on both posts -no start. start wire lights grounded test light when key turned to start position. Jumping hot battery post to small left post starts and runs with ignition on. Harness only has the one L shaped connector. A small card with the relay said cars with one wire should connect should use small right terminal with illustration, this didn't seem right to me knowing jumping to left post accuates starter. I'm still confused?
 

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Non-whiner
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10,646 Posts
Don't know where you read that, but the small left post is "S" for start. The small right post "I" is for ignition, but is not used.
 

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FFCobra Craftsman
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3,806 Posts
So, if you apply 12V to the small left post with a jumper from the battery post, the relay closes and the engine starts. But if you apply power to the small left post via the little R/LB wire with the "L" connector, the relay will not close and the engine will not crank.
Are those two sentences both true?????? If so, make sure the relay housing is well grounded to the frame. What gauge jumper wire are you using?
 

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FFCobra Craftsman
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3,806 Posts
Jeff, why do you say that? I'm guessing it has to do with the EMF diode inside the newer 3-post relays. Older style relays don't have a diode?
 

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FFCobra Master Craftsman
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2,033 Posts
You are correct it has to do with the diode. Ford had a TSB on this a long time ago. I can't find it at the moment.
Jeff Hamilton
 

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FFCobra Craftsman
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3,806 Posts
What you advise makes sense. Without the diode the collapse of the field in the relay will send a high voltage spike back up the R/LB wire to the ignition switch. Once there it will jump to the battery terminal inside the switch. I can see that high voltage jolt to the electrical system not being good for the computer. After extended use the contacts in the ignition switch (or any switch controlling a relay w/o an EMF diode) will also get burned and pitted.
 

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Premium Member
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6,408 Posts
Interesting...Could an EMF diode be placed in the r/lb wire , to protect the circuit?..If so , what size diode to use?
 

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FFCobra Craftsman
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3,806 Posts
Sure. Splice the negative end (end with the stipe) into the R/LB wire. Attach the positive end of the diode to ground. When the field in the coil collapses, the polarity also reverses. So, the negative end of the diode will then be attached to the negative side of the coil. The high voltage created will harmlessly flow through the diode to ground. A diode rated for 1 amp should be more than enough. You're dealing with high voltage, low amperage. A 1/2 amp diode would likely be enough.
 
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