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1981 Honda CX500c "Black Widow"
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55 Posts
Discussion Starter · #1 ·
My headlight was working but the idiot light wasn't so I added another blue wire to make the idiot light work. I tested it before I taped everything up and it worked. Now with everything taped, and installed it doesn't work.

At the high beam switch, I have a blue wire, blue/white wire and a white wire.

When the key is turned on and high beam switch down:
Blue - 3v
Blu/Wht - 2.6v
Wht - 2.6v

Switch up:
Blue - 3v
Blu/Wht - 3v
Wht - 2.6v

At the headlight, I have 2 blue wires going into a double bullet connector and white going in to a single connector then ground. I have verified the headlight works by hooking it directly to my battery.

Shouldn't I be getting 12v's in the first place? My blinker switch wires do.

I'm stumped, any help would be great.
 

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Super Moderator
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5,339 Posts
The Blue/White wire should have 12 volts, coming from the headlight fuse. The 12 volts is supplied to the fuse by a wire from the start button. The 12 volts only passes through the start button switch when the button is released. Do you have 12 volts coming from the start button?
Don't forget the ground side of the circuit. Are all the ground connections good?
 

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Super Moderator
'84 CX650E that is evolving into a GL500
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17,740 Posts
Just to clarify:
blue = high beam
white = low beam
blue/white = power to both beams (from the Start button's second set of contacts)

At the headlight plug, one blue wire comes from the high/low switch and the other goes to the high beam indicator.

The Start button has 2 sets of contacts, one set to send power to the solenoid when you press the button and the second set to interrupt power to the headlight while the starter motor is running so that all of the battery's power is available for the starter.

Where are you putting the meter's negative lead when you measure the voltages? For best results it should be connected to a green wire.
Note that all of the lights, horn &c should have their return current paths (to battery negative) through the green wires and not by being grounded to the frame.

There should be no voltage on the white wire when the high/low switch is in the high position and no voltage on the blue when the switch is in the low position. As Mike said, you should have 12V (actually full battery voltage so about 13V) on the blue/white wire when the switch is in either position.
 

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Registered
1981 Honda CX500c "Black Widow"
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55 Posts
Discussion Starter · #4 ·
Thank you both for the comments. I traced my blue/white wire back thru my fuse box and into my RH control and found the the black/yellow wire was not connected to my starter button.

My starter button only has 2 wires, not 3 like the original button, it's an aftermarket control. I see no way of connecting it to my start button so I think I have to put in an individual switch to turn the headlight power off manually before I hit the starter button.

Unless there's a trick around this?
 
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