reserve lighting unit

[canyon_jack]

if the reserve lighting unit is bad how does it effect the lights?according to my yamaha factory manual 6-17 and 6-18 it seems to control whether the lights will or will not work. page 6-18 mentions checking for 12v on the wires. how do i do that?

my brake light works but the headlight and front/rear turn signals do not. the lights in the central cluster between the speedo and rev counter work too.

the bike was in some state of disrepair when i bought it.

I am new to electrical issues hence my question - hope it does not seem silly.

1979 xs eleven special

[bikerphil]

The RLU will automatically switch headlight bulb filiments in case one should burn out. Your headlight is operated by a relay, which is triggered by the alternator when the bike fires up and starts charging. If the charging system is not functioning, the headlight will not come on. If you have the original glass type fuse box, that is a main trouble spot on these bikes. It can be upgraded to the newer blade type fairly easily.

[canyon_jack]

i replaced the fuse panel with the topcat one.
battery is at 12.5v at idle and increases to 13.5 ish at 2000k
where is the headlight relay? under the tank?
thanks

[bikerphil]

Yep, it's right above the coils. It can be bypassed by unplugging it and jumping the blu/blk and red/yel wires in the plug connector. The headlight should come on when the key is turned on.

[canyon_jack]

great. i'll try that tomorrow. it'll help me with my diagnosis.

so far .. i opened the left handlebar switch and blew it out and worked the switches. the wires are intact and switches move okay. horn works too.

also pulled headlight and inspected bulb. it looks good too.

when the manual mentions testing to see if there is 12 v on a wire what does it mean? engine on? where do i connect the multimeter? neg battery and ??? or positive battery and ???

you can tell i am really new to automotive electrics. i can swap a clutch in my driveway on my 4x4 but can nt make the headlights work on my bike!

thanks

[bikerphil]

Take the headlight assembly out and unplug it. Start the bike and check for voltage at the plug, blk is ground, green is lo beam, yel is hi, IIRC. If there is 12v, then the bulb is bad. If there is no voltage, I would bypass the relay as explained earlier. Try these tests first and go from there.

[TopCatGr58]

Hey there Jack,

I got your EMAIL and sent you a lengthy reply, hopefully explaining the basics of the multimeter and how to use it in both voltmeter mode and Ohmmeter mode. Let me know if you have more questions, or post to this thread, and let the REAL electrical gurus assist you!

T.C.

[canyon_jack]

cheers!

jack

[canyon_jack]

found the following:
1. power at all fusebox connections
2. headlight illuminates when by-passing the headlight relay. so relay might be bad.
3. 'cooked' generator connector (the one with the white wires) behind fuse panel, maybe causing the headlight relay to misbehave. wires check out so
will start with replacing the connector.

so i am making progress. more later.

[skids]

Yep, a bad connection at the alternator clip will definately do that. The tach and the relay depend on current from the alternator. If that dosn't do the trick, replace the relay with an automotive lighting relay. On the 78 and 79's you can use the switch from the handlebar to switch on/off the headlights if you go that route. I prefer it.

[canyon_jack]

update....i can see clearly now

i installed a replacement headlight relay as well as some new wiring connectors/plugs (4 plug from the stator and 3 plug for headlight) started the bike and hurray ...... the headlight works. the high/low switch on my bars works. still no turn signals but i'll be tracing those electrics tomorrow.

[DAVINCI]

Yep, a bad connection at the alternator clip will definately do that. The tach and the relay depend on current from the alternator. If that dosn't do the trick, replace the relay with an automotive lighting relay. On the 78 and 79's you can use the switch from the handlebar to switch on/off the headlights if you go that route. I prefer it.

I found the typical Bosch relay was not reliable in this application, I'm pretty sure it's because the alternator puts out 7-10VAC on each phase and the relay is looking for 12VDC. My solution was to gang two phases together with blocking diodes. It works.

[3Phase]

Thanks, Randy, that's a handy piece of information to have right there!