Head light issues

[donebysunday]

Went to go for a night ride last night, started it and the lights did not come on for a second, then lights come on thinking this is not good at night I hung close to home. Noticed the head light dimmed a few times just slightly. I was thinking old fuse box then the lights went out 4 blocks from home, I hit the high beam and the low beam came on and the light in the dash indicates beam failure, oh so it's the head light, no cars around so I hit the high/low beam a couple times and everything went back to normal.
I'll check the fuse block ( order a new style ) and the wires in the head light bucket.

Any other ideas ? Relay, charging ?

[DGXSER]

There are a couple items in that circuit. One is the relay that only lets the light come on when the charging system is putting out voltage. The other is the RLU which is a monitoring unit to detect if your low beam goes out and automatically switch to the high beam and light the indicator.

My best guess is your high low beam switch needs cleaning and or has a loose wire in there. However, it could also be the RLU is acting up. It can be bypassed. I think there is a tech tip on how, you jump two wires together, the blue black and the blue yellow.

[crazy steve]

Before you blame the RLU, make sure all your connections are good. Poor connections is a very common issue on these. The headlight relay is a 'latching' type that closes upon power being applied and won't open until power is fully removed (bike shut off) so I doubt that's your problem.

[GLoweVA]

Before you blame the RLU, make sure all your connections are good. Poor connections is a very common issue on these. The headlight relay is a 'latching' type that closes upon power being applied and won't open until power is fully removed (bike shut off) so I doubt that's your problem.

+1 on that, also if that relay was bad, then you'd lose your dash lights too.

Sounds like a high resistance connection at the fuse supplying the headlight/dash lights.

[donebysunday]

+1 on that, also if that relay was bad, then you'd lose your dash lights too.

Sounds like a high resistance connection at the fuse supplying the headlight/dash lights.

Thanks Guys ! THE DASH LIGHTS DID GO OUT TOO ?

[dondons1984]

so just my two cents and I by no means know anything but check the fuse box to make sure its clean and the connections to the headlight. I know mine did that and I found out that the metal cliip that holds the fuse it was a little worn out and having issues holding the fuse. again just my opinion.

[donebysunday]

head light

Well just started the bike and no lights, dash or head light.
I have turn signals, flasher and tail light but no dash or head light high or low.
Checked the fuses seem good, checked the volts and at 3K measure 14.5.
Next onto the handle bar switch. If this is good where is the relay ?

[DGXSER]

First, make sure you check the wire leaving the fuse box, not the end of the fuse for power. The fuse may be conducting it to the connector, but the connector may not be transferring the power to the wire.

The headlight relay is up by the coils, under the gas tank. If your losing power to the lights in the dash, then it is before it gets to the dimmer switch on the left handlebar. That only controls the headlight.

Power goes to the headlight fuse, then the red/yellow goes to the headlight relay. The Blue/Black wire leaves the relay to go to the RLU, and to the dash lights. The power goes through the RLU to get to the dimmer switch.

[donebysunday]

relay

Found the relay under the tank in the frame took it apart sanded the contacts, seems someone was there before. No luck still no headlight or dash lights ? ? ?

Thanks Don !!!!!

[DGXSER]

Your welcome Done!

Turn the key on and check for 12-14V at the red/yellow wire of the harness side of the relay connector. If it is there, then you can jump the red/yellow and the blue/black wires in the harness side of the relay connector and see if the headlight comes on. You can try this with the key on and the tank off, your bypassing the relay so the engine does not need to be on for the headlight to function. You should definitely at least get dash lights then.

[bikerphil]

You can unplug the headlight relay and bypass it by jumping the red/yel and blu/blk wires, see if the headlight comes on with the key in the on position.

[DGXSER]

If it helps any, I drew up this simplified diagram of the headlight circuit. I skipped the RLU stuff except the main power components.



I used both colors for the two color wires..red/yellow, blue/black, and blue/yellow.

Note the wires to the dashlights are just blue no black in them.

[donebysunday]

Your welcome Done!

Turn the key on and check for 12-14V at the red/yellow wire of the harness side of the relay connector. If it is there, then you can jump the red/yellow and the blue/black wires in the harness side of the relay connector and see if the headlight comes on. You can try this with the key on and the tank off, your bypassing the relay so the engine does not need to be on for the headlight to function. You should definitely at least get dash lights then.

Thank You Don and ALL trying to help me !!!!!

Checked the voltage at the batt. 12.65, engine running at 3K 14.50, Checked at the R/Y and 11.65.

Jumped the R/Y to the BL/BLACK and I have head light and dash lights, HI and LO beam.
So I could just leave these jumped and go but I'd like to resolve what the real culprit is !

(It always bugged me that the head light would come on and if the bike did not start the head light stayed on, so I'd switch off the key to kill the head light and try starting again continue this on/off ign. until it started.) Awe but this is for another post.

I'm thinking check the relay with the cover off to see if it's getting the power from the alt/gen. ?
OK the relay closes when the bike starts so it's getting the power from the alt/gen..
Funny thing as soon as the engine stops the relay opens back up again even with the key left on. At this point the engine will only run in the choke pos. as the fuel level is low in the carbs, just flip off the choke and engine stops.
Still the relay does not activate any lights. So I'm thinking bad relay ? ? ?

[DGXSER]

Based upon the fact you have 12 volts at the red/yellow, and jumping that to the blue/black gives you fill functioning headlight and dash lights, yes you have a bad relay.

Since it is a latching type relay, it stays closed once it closes until it loses power to the both sides. Meaning, under normal operation, once the headlight comes on, it will stay on until you turn the key switch off, or you pull the fuse to the headlight to kill the power to that red/yellow wire.

Once it is open again, it will not close until it gets power to the white wire of the relay, which happens when the alternator puts out power, then engine is running.

You could simply leave the jumper in place between the red/yellow and blue/black wires (in a "permanent" manner with some protective covering), or you can replace the relay. The reason for the relay is to take that headlight load off your battery when it is starting the engine.

[GLoweVA]

Since it is a latching type relay, it stays closed once it closes until it loses power to the both sides. Meaning, under normal operation, once the headlight comes on, it will stay on until you turn the key switch off, or you pull the fuse to the headlight to kill the power to that red/yellow wire.

Once it is open again, it will not close until it gets power to the white wire of the relay, which happens when the alternator puts out power, then engine is running.

+1 agree that's how the Yamaha relay works.
This assuming of course that the relay he has is the stock relay and not some off the shelf automotive relay. Which would turn off/open once power goes away.

Edit: of course the 78/79 relay is different than the 80/81 relay.