Coil Relay Mod Question on pin 86

[Guest]

I have two orange/white wires coming from the harness, each with a connector to its respective coil. I'd like to avoid disrupting the harness by unwrapping for several inches to get back to the point before they branch.

Can I use just one of the o/w wires to switch the relay, or does it need both?

If both, can I siamese the two o/w wires into a single connector and plug that onto pin 86 of the relay?

I'm sorry that this is a dumb question, and I think either solution would work. But electricity is my weakest mechanical skill, so I'm looking for some confirmation before I ruin a nice GS.

Thanks.

[mike_of_bbg]

You only need one feed to the relay to switch it on. You'll want to feed both coils from the relay though (sorry can't remember the pin #'s). One lead to activate the relay IIRC my coil leads were about 3 inches long so I just cut those and left the harness unmolested. The rear brake switch seems to be a popular place to grab switched B+ to activate the relay. On my bike the Dyna was already fitted so I grabbed it from the ignitor harness.

I have two orange/white wires coming from the harness, each with a connector to its respective coil. I'd like to avoid disrupting the harness by unwrapping for several inches to get back to the point before they branch.

Can I use just one of the o/w wires to switch the relay, or does it need both?

If both, can I siamese the two o/w wires into a single connector and plug that onto pin 86 of the relay?

I'm sorry that this is a dumb question, and I think either solution would work. But electricity is my weakest mechanical skill, so I'm looking for some confirmation before I ruin a nice GS.

Thanks.

[koolaid_kid]

It is not a dumb question, trust me. Here is what I recommend:
Unplug both O/W female spade connectors from the coils. Wrap one up in electrical tape and put it aside (I generally prefer zip tying it in place).
Make a jumper wire, it should have a male spade connector on one end, plug that into the remaining O/W female connector that used to be connected to the coil.
Run that wire to your relay terminal 86. This becomes the trigger voltage to activate the relay.
Run a wire from relay terminal 87 to both coils. I use a tap solder joint for the Y to go to each coil, but there are many ways to skin this rabbit.
If you do it this way, your wiring harness is completely unmolested, with no cut wires, and you can go back to stock if something unexpected happens to the relay circuit.
Also, be sure you put a fuse in the wire going to terminal 30. If all you are powering is the coils, they only pull 8 amps, so a 10 amp fuse is ample.
Best of luck, hope this helps.

[FiremanBob]

A new problem: I can't tell what kind of connectors link the orange/white wires to their terminals on the coils. The connection is covered in some sort of hard plastic sealant that was originally dripped onto it. I'm reluctant to destroy that connection and then find I have no way to connect power from the relay to the coil. If they are spade connectors, that's ideal, but if they are somehow bonded to the coil I'd be screwed.

But those orange/white wires are only 18 gauge, which seems awfully puny for powering the spark. I'd like to replace them with the same 12 gauge wire I have from the solenoid to the relay.

Would much appreciate expert advice on this.

[BassCliff]

Hi,

I crimped both o/w wires into the same blade connector when I installed my coil relay mod. It's been working just fine. You can see my coil relay mod story here:

More On Coil Relay Modification

I snipped the wires on the harness side of the connector. I have a jumper that I can install to put the circuit back to (basically) stock if my relay goes bad and I don't have a spare.


Thank you for your indulgence,

BassCliff

[koolaid_kid]

A new problem: I can't tell what kind of connectors link the orange/white wires to their terminals on the coils. The connection is covered in some sort of hard plastic sealant that was originally dripped onto it. I'm reluctant to destroy that connection and then find I have no way to connect power from the relay to the coil. If they are spade connectors, that's ideal, but if they are somehow bonded to the coil I'd be screwed.

But those orange/white wires are only 18 gauge, which seems awfully puny for powering the spark. I'd like to replace them with the same 12 gauge wire I have from the solenoid to the relay.

Would much appreciate expert advice on this.

If they are factory coils they have a spade connector. You could put connectors further down the line if you want, but both coils need to have the OEM connections removed.
AFA the gauge of the wire, most of the wiring on our bikes is inadequate. However, 12 gauge is overkill. I went to a couple of on-line calculators for determining wire gauge vs. power requirements (current and voltage) over distance. Your coils draw around 4 amps at 12 volts, which is 48 watts, and the length of the wire should not be over 3 feet or so. For this amount of power handling with the preferred less than 2% loss over the length of the wire, 16 gauge is fine, 14 gauge will work but is overkill.
Also, remember the function of an ignition coil. It does not amplify current (which is the main determining factor for selecting a particular gauge wire) it amplifies voltage. So you put 12 volts in through the O/W wires, it multiplies it (how much can calculated if you know the number of windings in the coil) and it comes out at 28-32 thousand volts. So your goal should be to deliver the 12 volts (nominal, actually closer to 14 volts at speed with a good charging system) so the output voltage is as high as possible.

[FiremanBob]

Finished the mod today

After work today I finished the coil relay mod. The bike started right up and even after the engine was warm continued to idle smoothly at about 1100 rpm. This is a dramatic improvement over the way it ran during the previous three weeks.

As to the original question in this thread, as one helpful responder said, the coils don't take much current, so siamesing the two orange/white wires from the coils onto the output terminal of the relay (87) is fine. I cut one o/w wire from the harness side of one coil connector, added a short length of wire for slack up to the relay and it powers the switch now (on terminal 86).

A few hard lessons learned:

1. The 5-pin relay I bought at first didn't have two outputs that were on/off at the same time. It used the relay to switch between the two outputs, so one coil was getting 12v when the bike was off, and the other when the bike was on, but never both at the same time so the engine ran on two cylinders. I learned this only after a few days of wondering if I had a bad coil or a bad igniter and spending enormous time figuring out how to check both.

2. BassCliff's article about fixing the coil was very handy. I used his instructions to re-solder the 12v and igniter wires back onto the coil, and some epoxy putty to hold it all together. My job isn't as neat as his but I don't think it will ever fall apart.

Thanks for all the help, here and on the other thread.