Find Headlight Low Beam Wire - 2012 Honda Shadow Phantom
- Thread starter Corsair
- Start date
silverbullet132
Well-known member
Multimeter?
If the wire reads voltage, then goes to 0 once you flip on high beams, that wire is low beam. etc.
Ed In Mississauga
Well-known member
Wire colours vary for each manufacturer and to an extent each model... find a service manual online and look up the wiring diagram. Either that or unplug your headlight, use a multimeter to test. Black lead to ground and then red lead to find which wire gives you 12V with your low beam on.
The wires will be coloured. The colour codes will only be meaningful if you have the wiring diagram in the workshop manual, because that will explain which wire does what.
Undo the plug to the headlight. Presumably it is a normal 3-prong connector. Set your multimeter to measure resistance (the lowest resistance scale available, ohms). Have the key off. Measure the resistance with one multimeter lead held against a good solid chassis ground (e.g. the engine block) and probe the other three terminals on the connector (it's easy to stick the probe inside the connector - that's what it's for). The one that gives you near zero resistance (a fraction of an ohm) is the ground terminal.
Now set your multimeter to measure DC voltage. Turn on the key, and if necessary, start the engine to turn the headlight on (some bikes require the engine to be running in order to activate the headlight). No, the headlight will not actually come on, because you have the plug disconnected, but it will turn on power to the plug in an attempt to do so. Measure voltage between that good chassis ground and each of the three terminals. As a double-check, the one that you identified as ground above, should give zero voltage in either low-beam or high-beam switch positions. Which of the other two terminals is the low-beam side ... will be a no-brainer to figure out at this point.
N.B. Some headlight circuits feed constant power to the common terminal on the headlight connector and activate the beam by switching to ground. I've seen some cars do it this way but I've never seen a bike do it that way.
Also, if there is any possibility to do so at all, pull the switched power from a circuit other than the headlamp circuit, even if you have to run a wire from somewhere else on the bike. Switched power for the taillight circuit would be my choice.
Reason: I don't trust aftermarket stuff. If you have a short-circuit in your wiring or in the aftermarket component, it's better for it to blow the taillamp fuse than the headlight fuse. I've had a headlight fuse blow at night and had to make my way home by the dim light of the "city light" and the intermittent yellow light of a flashing turn signal ... it's good to have the forward lighting on the bike fed from two separate circuits ...
Undo the plug to the headlight. Presumably it is a normal 3-prong connector. Set your multimeter to measure resistance (the lowest resistance scale available, ohms). Have the key off. Measure the resistance with one multimeter lead held against a good solid chassis ground (e.g. the engine block) and probe the other three terminals on the connector (it's easy to stick the probe inside the connector - that's what it's for). The one that gives you near zero resistance (a fraction of an ohm) is the ground terminal.
Now set your multimeter to measure DC voltage. Turn on the key, and if necessary, start the engine to turn the headlight on (some bikes require the engine to be running in order to activate the headlight). No, the headlight will not actually come on, because you have the plug disconnected, but it will turn on power to the plug in an attempt to do so. Measure voltage between that good chassis ground and each of the three terminals. As a double-check, the one that you identified as ground above, should give zero voltage in either low-beam or high-beam switch positions. Which of the other two terminals is the low-beam side ... will be a no-brainer to figure out at this point.
N.B. Some headlight circuits feed constant power to the common terminal on the headlight connector and activate the beam by switching to ground. I've seen some cars do it this way but I've never seen a bike do it that way.
Also, if there is any possibility to do so at all, pull the switched power from a circuit other than the headlamp circuit, even if you have to run a wire from somewhere else on the bike. Switched power for the taillight circuit would be my choice.
Reason: I don't trust aftermarket stuff. If you have a short-circuit in your wiring or in the aftermarket component, it's better for it to blow the taillamp fuse than the headlight fuse. I've had a headlight fuse blow at night and had to make my way home by the dim light of the "city light" and the intermittent yellow light of a flashing turn signal ... it's good to have the forward lighting on the bike fed from two separate circuits ...
frekeyguy
Well-known member
Those plugs usually have a exposed back to them.
Stick the prongs on the multimeter into the back of the plug or in the front.
If you don't have a multimeter .... Cut one wire (not ground) Nd flick your switch. If low works and no high - then you know the wire that was clipped is the high. And vice versa.
Stick the prongs on the multimeter into the back of the plug or in the front.
If you don't have a multimeter .... Cut one wire (not ground) Nd flick your switch. If low works and no high - then you know the wire that was clipped is the high. And vice versa.
RC-31
Well-known member
All the Hondas I've worked on have had a green ground, a white lowbeam and a blue highbeam.
There is also a light blue and a light blue with a white stripe that are for the right side turn signal and marker light respectively.
This is not comprehensive info, and I don't ever work on electrics without a wiring diagram; but this should be enough info to get you started.
There is also a light blue and a light blue with a white stripe that are for the right side turn signal and marker light respectively.
This is not comprehensive info, and I don't ever work on electrics without a wiring diagram; but this should be enough info to get you started.
I personally would not tap into the headlight for Brian P's reasons.
I am sure there's an accessory wire that you can tap into that is only active when the key is on.
You may want to look for that and leave the headlight alone.
Don't worry about turning the LEDs off when the high-beam is on.
I am sure there's an accessory wire that you can tap into that is only active when the key is on.
You may want to look for that and leave the headlight alone.
Don't worry about turning the LEDs off when the high-beam is on.
Corsair
Well-known member
D'oh! Totally forgot the low-beam switches off when the high-beam is on!
Dug up a 2009 service manual. I'm going to look for an alternate line and leave the headlight alone, per Brian P. Don't want to end up duct-taping a flashlight to the handlebar to get home
I've done plenty of house wiring but first time fidgeting with automotive wiring, so a little wary. Thank you all for your feedback.
