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Discussion Starter #1 (Edited)
Until today, my heated grips were hard wired to my battery. Which was fine provided I forgot to turn them off.

I recently ordered some automotive relays and thought the area under the seat would be an ideal location to mount it.

Looking around for an appropriate wire to tap, the license plate lamp looked convenient and pretty benign should it not be a smooth undertaking.

Anyway, the relay and grips work as they should when everything's connected. However, the license plate lamp doesn't illuminate.

It's wired up as follows: Blue (#30 from battery), yellow ($87) to grips. Black (85) and white (86) wires are connected to the lamp wiring. The red wire, #87A, is unused (5 pin relay).

Reversing the white/black wires from the relay doesn't fix the problem.

When I connect the original wires together again, it the light works as it should.

So, there's switched voltage at the relay to close and power the grips, but nothing for the lights.

I'm left to think that there's too much of a voltage drop across the relay and not enough power left to light the bulb.

In the meantime, does anyone have any explanations? Is there a better switched wire to tap into that runs under the seat?
 

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I don't see the wiring diagram you are referring to so have no idea function those wires serve. Also, what year KLR is it.

You need to tap one relay holding coil wire to the tail/tag light wire to activate the relay and run the other holding coil wire to ground. Then run the main FUSED power wire from the battery to one of the normally open contact wires of the relay and the wire other from the other side of the normally open contacts goes out to the grips. Then the other side of the grips goes to ground.
 

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Discussion Starter #3 (Edited)
Update:

Just replaced the batteries in my multimeter and grabbed a flashlight.

Switched voltage is 11.6 V at the relay and only milivolts being supplied to the light.

These are 5 pin ebay "specials". I'll stop by the parts store tomorrow and get a simpler 4 pin relay and try again.
 

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Generally I think you'd want to wire it this way, using the tail light wire as the trigger and taking power straight off the battery.


If you wired it like this, taking power from the tail light wire, then the grips would consume enough power to prevent the tail light from illuminating.


Note: Tail Lamp, License Plate Lamp, same-same.

Tom
 

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Discussion Starter #5
Generally I think you'd want to wire it this way, using the tail light wire as the trigger and taking power straight off the battery.




Note: Tail Lamp, License Plate Lamp, same-same.

Tom
Yes. The tail light is the "trigger".

Left and right is a trigger (85 and 86), top and bottom power the grips (30 and 87) just as it should be according to any number of schematics I've looked at. The center pin, #87A, is unused.

Interestingly, if I remove the downstream trigger (86) and connect the supposedly unused wire (Normally closed 87A) in it's place, the tail lamp is always light, even when the bike is turned off. So, correct wiring yields no downstream trigger voltage and a supposedly unused wire is always hot. Weird.

As I mentioned above, I think a simpler 4 pin relay is the next step.
 

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Why are 85 and 86 both connected to the lamp wiring? One should be connect to ground. You are grounding the solenoid through the license plate light.

Tom
 
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Discussion Starter #7
Why are 85 and 86 both connected to the lamp wiring? One should be connect to ground. You are grounding the solenoid through the license plate light.

Tom
Without the input trigger connecting at 85 and output trigger wired to 86, how would there be a complete circuit for the tail light? There'd be no voltage applied to the hot side of the lamp otherwise, right? Right? :/
 

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Without the input trigger connecting at 85 and output trigger wired to 86, how would there be a complete circuit for the tail light? There'd be no voltage applied to the hot side of the lamp otherwise, right? Right? :/
You're not affecting the circuit for the license plate light in any way. The only thing you are doing is tapping into the positive lead of the lamp light to serve as a trigger (i.e. impart power) to the relay. Remember, PIN30 (direct to your battery) is NOT powering the relay; PIN30 is powering your accessory. PIN85 is what's powering your relay, and in your case this is done with PIN85 tapped into the positive wire to the lamp. When the key is turned on, power goes to the light and the relay.

The relay itself is an electrical device that requires grounding, via PIN86. The best grounding solution is the negative terminal on your battery, but you can use any suitable ground.

You've figured out that the 87 PINS are the accessory pins. PIN87 is "a normally closed circuit" and PIN87A is "a normally open circuit." So, a circuit along PIN30 to PIN87 opens when the trigger source is powered; the circuit along PIN30 to PIN87A is closed when the trigger source is powered. There are applications for a 5 pin, but it should work fine in this situation. Connect the positive wire to your accessory to PIN87.

Similar to the relay, your accessory needs separate/discrete grounding. Again, ground it separately to the negative terminal on the battery or other suitable grounding source.

Okay....

Now if, as you say, you had PIN86 tapped into to the negative wire to your lamp light I might have thought that this whole thing would have worked. That is, the negative wire to your lamp light might have been sufficient grounding for the relay. Maybe not, I don't know. First thing though is to move your ground on PIN86 to the negative terminal to your battery.

If that doesn't work, test your trigger power using a circuit tester and relay with your multimeter. Use a circuit tester and make sure the wire your using for the trigger lights your circuit tester light only when the key is on. On the relay, put your multimeter on ohms. First, with nothing connected to the relay, check to see if there is an open circuit between PIN30 and PIN87A; there should be. Then connect PIN85 to the positive battery terminal; connect PIN86 to negative battery terminal. That should create an open circuit between PIN30 and PIN87. If either didn't work, the relay is probably bad. Like any electrical component, relays can be damaged.
 

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Discussion Starter #9
You're not affecting the circuit for the license plate light in any way. The only thing you are doing is tapping into the positive lead of the lamp light to serve as a trigger (i.e. impart power) to the relay. Remember, PIN30 (direct to your battery) is NOT powering the relay; PIN30 is powering your accessory. PIN85 is what's powering your relay, and in your case this is done with PIN85 tapped into the positive wire to the lamp. When the key is turned on, power goes to the light and the relay.

The relay itself is an electrical device that requires grounding, via PIN86. The best grounding solution is the negative terminal on your battery, but you can use any suitable ground.

You've figured out that the 87 PINS are the accessory pins. PIN87 is "a normally closed circuit" and PIN87A is "a normally open circuit." So, a circuit along PIN30 to PIN87 opens when the trigger source is powered; the circuit along PIN30 to PIN87A is closed when the trigger source is powered. There are applications for a 5 pin, but it should work fine in this situation. Connect the positive wire to your accessory to PIN87.

Similar to the relay, your accessory needs separate/discrete grounding. Again, ground it separately to the negative terminal on the battery or other suitable grounding source.

Okay....

Now if, as you say, you had PIN86 tapped into to the negative wire to your lamp light I might have thought that this whole thing would have worked. That is, the negative wire to your lamp light might have been sufficient grounding for the relay. Maybe not, I don't know. First thing though is to move your ground on PIN86 to the negative terminal to your battery.

If that doesn't work, test your trigger power using a circuit tester and relay with your multimeter. Use a circuit tester and make sure the wire your using for the trigger lights your circuit tester light only when the key is on. On the relay, put your multimeter on ohms. First, with nothing connected to the relay, check to see if there is an open circuit between PIN30 and PIN87A; there should be. Then connect PIN85 to the positive battery terminal; connect PIN86 to negative battery terminal. That should create an open circuit between PIN30 and PIN87. If either didn't work, the relay is probably bad. Like any electrical component, relays can be damaged.

Thanks for the explanation.

There is about 80 ohms resistance between pin 85 and 86. This falls into the normal range for the coil, so I assume that it's good. There's also a voltage drop. I also got the same readings with a second relay that was part of the order. I think it's safe to say that the relays are good and the problem lies with the installer.

The difficulty I'm facing is not understanding wires.

The Navy trained me to troubleshoot electronic circuits and very little about wires. LOL. It's also not helping that we were taught "hole" flow (positive to negative) and not electron current flow (negative to positive). I seldom consider grounds in the overall scheme of things.
 

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You're on the right track. It's your relay ground that's the issue.

Wire 85 to lamp hot side of lamp. Fuse with 1 amp fuse if you want to. Then if relay or wire shorts, 1 amp blows and your light fuse does not. Locate fuse as close as you can to "tap in" location.

Wire 86 to chassis or battery ground. NOTE: I use a chassis so I don't have to remove it just to swap a battery.

Fuse relay term 30 at positive battery as close as is reasonably possible. Use fuse that is same rating as grip fuse. NOTE: I wire to starter solenoid hot side (NOT BATTERY) so I don't have to remove a bunch of wires just to swap a battery.

87 is hot feed for grips.

**************
SIDE NOTE: OXFORD BRAND HEATED GRIPS SHUT THEMSELVES OFF WHEN VOLTAGE GETS LOW.

FOOD FOR THOUGHT: Consider wiring 87 to the feed side of a aftermarket fuse block. That would leave room for future switched accessories independently fused from each other. You never know what the next doodad will be that you'll add.





 

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Discussion Starter #11
You're on the right track. It's your relay ground that's the issue.

Wire 85 to lamp hot side of lamp. Fuse with 1 amp fuse if you want to. Then if relay or wire shorts, 1 amp blows and your light fuse does not. Locate fuse as close as you can to "tap in" location.

Wire 86 to chassis or battery ground. NOTE: I use a chassis so I don't have to remove it just to swap a battery.

Fuse relay term 30 at positive battery as close as is reasonably possible. Use fuse that is same rating as grip fuse. NOTE: I wire to starter solenoid hot side (NOT BATTERY) so I don't have to remove a bunch of wires just to swap a battery.

87 is hot feed for grips.

**************
SIDE NOTE: OXFORD BRAND HEATED GRIPS SHUT THEMSELVES OFF WHEN VOLTAGE GETS LOW.

FOOD FOR THOUGHT: Consider wiring 87 to the feed side of a aftermarket fuse block. That would leave room for future switched accessories independently fused from each other. You never know what the next doodad will be that you'll add.





Nice. Thanks!

Again, "hole" flow seems to affect my understanding of DC circuits.

I tapped pin 85 on the battery side of the wire thinking that I needed a + source. Pin 86 continues to the lamp and, to my mind, completed the circuit.

It seems that I needed to understand that I could draw a trigger from the tail light directly to feed the relay and then ground from there.

I guess my question now is what do I do with the snipped tail light wire that connects to the bike's wiring harness? Tape it and it fold it out of the way?
 

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Just wondering, why not tap the BROWN wire for the relay control ("trigger") voltage?

BROWN is switched + 12 VDC.

Nothing wrong with using the tail/license lamp lead, but . . . tapping BROWN (maybe with one of those little plastic connectors that folds over the connection) doesn't mess with any other circuits.

A "solid state" mindset interfered with this non-transistorized hook-up, I think! :)
 

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Nice. Thanks!

Again, "hole" flow seems to affect my understanding of DC circuits.

I tapped pin 85 on the battery side of the wire thinking that I needed a + source. Pin 86 continues to the lamp and, to my mind, completed the circuit.

It seems that I needed to understand that I could draw a trigger from the tail light directly to feed the relay and then ground from there.

I guess my question now is what do I do with the snipped tail light wire that connects to the bike's wiring harness? Tape it and it fold it out of the way?
85 to key on hot
86 to ground

or

86 to key on hot
85 to ground

Your choice.


You should hear the relay click when key is turned on and off.

I think the way you had it wired it was causing the license plate ground wire to have a positive voltage in the ground wire preventing current to flow to ground through that path. Just wire like I said above. Holes or no holes, it will work. I still would fuse it. If you don't and something happens to the relay or your new wiring, you could blow the light fuse. Use a very low amperage fuse. It should blow before the light fuse will. Your grips will stop working but your lights will continue to burn. Always plan for failure!
 

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Discussion Starter #14
Got it. Everything's soldered and heat shrunk back in place.

I was placing the relay in series with the tail lamp. Instead, Pin 85 or 86 needed to be spliced in parallel (trigger wire in a three way splice with the tail lamp and then the other pin ran to ground).

I'll never understand why the relay can't be placed in series and the trigger current is unable to get a complete a path to ground *through* the tail lamp, though.
 

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Because, when things are wired in series, there is a voltage drop across each component in series. Current is constant across all the components. The voltage drop is proportional to the resistance of each component.

The resistance of the relay's coil and the resistance of the license plate lamp are of the same order of magnitude, so let's just say they are equal. That means the voltage drop across them is equal. Since there is only 12v available, the voltage drop across each one is 6 volts. By wiring the coil in series with the license plate lamp, you were giving the lamp 6 volts when it needs 12.

When things are wired in parallel the voltage is constant across all components, but the current at each component is proportional to the resistance.

This is true, and the forumulae are V=IR and P=IV.

These two concepts lead to Thévenin's theorem and Kirchhoff's Rules, a study which will make first year engineering students take to drink. At least, that's the excuse I used...

Tom
 
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When things are wired in parallel the voltage is constant across all components, but the current at each component is proportional to the resistance.
In a parallel circuit, the current is inversely proportional to the resistance, I think! :)

Or something. The greater the resistance, the smaller the current through a component in a parallel circuit.
 

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Discussion Starter #17
Because, when things are wired in series, there is a voltage drop across each component in series. Current is constant across all the components. The voltage drop is proportional to the resistance of each component.

The resistance of the relay's coil and the resistance of the license plate lamp are of the same order of magnitude, so let's just say they are equal. That means the voltage drop across them is equal. Since there is only 12v available, the voltage drop across each one is 6 volts. By wiring the coil in series with the license plate lamp, you were giving the lamp 6 volts when it needs 12.

When things are wired in parallel the voltage is constant across all components, but the current at each component is proportional to the resistance.

This is true, and the forumulae are V=IR and P=IV.

These two concepts lead to Thévenin's theorem and Kirchhoff's Rules, a study which will make first year engineering students take to drink. At least, that's the excuse I used...

Tom
Doh! I knew that at one point...

The impedance across the relay coil was on the order of 80 ohms. I'm uncertain of the resistance of the tail lamp filament.

One forgets that a measure so seemingly insignificant can cause enough of a voltage drop to cause problems elsewhere on the same leg.

Now if someone could only make the concept of a "common" in a household AC circuit I might finally have enough understanding of electricity to be dangerous. :nerd:
 

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Doh! ...........................Now if someone could only make the concept of a "common" in a household AC circuit I might finally have enough understanding of electricity to be dangerous. :nerd:
For your purposes just consider the ground wire (negative connection) in a DC circuit to be the same as "common" in a household AC circuit.

AC circuits connect back to the common in the breaker box.
DC circuits connect back to the negative side of the battery (ground).

On the KLR all ground wires are black/yellow (black with a yellow stripe). They all lead back to the negative side of the battery. Some lead to a bolt on the frame and through the frame to the negative side of the battery.
 
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