Headlight Relay Diode Repair

[3Phase]

Replacing the diode for the automatic headlight relay was much easier than I thought it would be at first.

The diode lives near the headlight relay in the wiring harness






Apparently this was a self-kill

I broke the diode when I was cleaning the connectors and the wiring




I traced the diode and headlight relay wire back to the splice and marked the correct white wire at the voltage regulator/rectifier connector

The middle white wire goes to the diode on my bike




After soldering in a new diode I put a neoprene hose over the diode and its connectors and kept it out of the main wiring harness bundle when I re-taped everything






While I was replacing the diode I noticed the rubber mount for the emergency ignition cutoff switch (the tipover switch) was torn and the switch was hanging sideways, sort of

Norwegian racing twine will have to suffice until I find another rubber mount for the switch




Regards,

Scott

[DJinNH]

Scott,

Pretty cool of you to photograph your step by step work and posting it here for others. I'll have to see if that solves the problem with my headlight not coming on.

Don

[John]

You can just remove the tip over switch, and get rid of it. All it does is ground the ignition circiut, when the bike is laid down. You don't need to do anything with the wire except tape it off.

[3Phase]

Don:

I hope it helps you and anyone else that has to find that diode. The photos other people have posted of their work, projects, troubleshooting, and general musings have been a great help to me.


John:

I gave it some thought before fixing the mount for the emergency switch. What convinced me to keep it was the thought of dropping her and having her come back and try to run me over a couple more times before giving up. Sort of like an ex, but with just a tad less glee....

Regards,

Scott

[AlanB]

Hi 3Phase,

I used to work in a Yam shop, and the company rep told us that a Jap test rider fell off one of the prototype 11s during development testing. The bike was in gear and had a full tank.

It sat on the frame rail and ran round in a little circle, wearing a hole in the tarmac until it ran out of fuel.....

Dunno if it is true, but the mental picture of the big Yam spinning round on the peg with the little rider running round in a circle, waving his arms still makes me smile........

I took the tilt switch off of mine; I reckon I am big enough to catch it!...LOL!

AlanB

[DJinNH]

Originally posted by John
You can just remove the tip over switch, and get rid of it. All it does is ground the ignition circiut, when the bike is laid down. You don't need to do anything with the wire except tape it off.

OK, confession time.

I spent two days going through wiring, circuits, etc trying to find out why my headlight didn't work. Now, I have mentioned before that I would never be confused with a real mechanic.

My bike had been starting great until I went on my hunt for the headlight issues. Finally, a friend of mine asked what I did after the bike was starting fine. He suggested going through everything I messed with and double checking it.

FINALLY, dingbat here found that when I was checking the little box for the tip over shut off, I had mounted it up-side-down. DUH! I remounted it the right way and surprise, surprise....the bike fired right up.

At least I learned about what one more part does on my bike and sure won't forget it anytime soon.

Don

[3Phase]

Watch this; hold my beer

Hey, Alan; that sounds like Keystone Test Riders or something. It's too bad YouTube wasn't around back then, but it is now and if you think you can catch a runaway XS11 -- go for it!

I'll hold your sign so you don't lose it!


Don, that almost happened to me. I stiched it backwards and upside down.

Fortunately, while I was buttoning up the rest of the harness, I saw some little raised letters on the switch that said "Upper" (Upper?) or I would have been pulling my hair out and wondering what went wrong this time, too!


Regards,

Scott

[egsols]

Don, that almost happened to me. I stiched it backwards and upside down.

That's wy my wife uses a sharpee to label by boots "L" and "R". I can't be expected to memorize everything!

[3Phase]

Originally posted by egsols


That's wy my wife uses a sharpee to label by boots "L" and "R". I can't be expected to memorize everything!

What?! There are right and left boots?!

No wonder my feet hurt; someone at the factory should label these things....


Regards,

Scott

[3Phase]

Here's an update with pictures after closing my Flickr Pro account.

The OEM diode is still available from Yamaha but it's expensive:

Partzilla | Yamaha | Motorcycle | 1980 | XS1100SG | Electrical 1:
31 DIODE 3H5-81980-00-00 $14.31 $9.34

Another option is your local Radio Shack, they should have a package of 1N4007 diodes.

1N4001 diodes will work if you can't find the 1N4007.

The harness diode is just aft of the Headlight relay and you'll have to peel back some of the wrap to find it. I traced the White wire back to the Regulator/Rectifier connector and marked it so I could find and test the diode if I needed to check it again..



"The Diode" 3H5-81980-00-00


The Headlight relay also has a diode inside it that is a 'latch' to keep the headlight on if the voltage drops or the engine dies.



To test the relay on the bike, turn on the ignition switch and jumper 12V to the White wire up at the relay or down at the Regulator/Rectifier connector. The relay should click and the headlight should come on and stay on even after you remove the jumper until you turn off the ignition switch.

B = Ground
R/W = 12V from the 10A Head fuse
W = wire from the alternator and has the diode inline
L/B = 12V out from the relay to the RLU



My replacement with a neoprene hose to cover and protect the inline harness diode:


The Tipover switch and my Norwegian racing twine repair for the rubber mount:

[motoman]

Nice repair option. Looks like hardest part would be threading the needle.

[3Phase]

Nice repair option. Looks like hardest part would be threading the needle.

The hardest part was finding good rubber on the mount that wasn't rotted and would hold thread without tearing, it was in bad shape from age, heat, ozone and whatever.

The posts and pictures are from back in 2008, before I named 'her' "Columbo". I didn't have spare parts or parts bikes and I was still learning about my first XS1100. The Tipover switch is still hanging in there with its stitched repair too. I have several good ones now but I keep using the repaired one because... because!

[SNDSLGR]

3phase .. so if im following you here, if the jumper wire activates the relay and kicks the HL on then im likely looking at a broken diode?

Just put a battery in my project finally

1) everything seems to work except headlight and gauge lights
2) headlight and spedo light works when i unplug the relay and jump R/Y x BL/BK
3) HL, spedo and tach light works when i jump from battery + to W on relay plug. relay clicks, all stay on until ignition is killed.

Wiring diagram shows that W wire comes from the alternator... would the fact that the bike is not running change any of this? (waiting on a few more carb parts before i can start it)
Thanks for your time.

(81' xs1100sh)

[3Phase]

3phase .. so if im following you here, if the jumper wire activates the relay and kicks the HL on then im likely looking at a broken diode?

Just put a battery in my project finally

1) everything seems to work except headlight and gauge lights
2) headlight and spedo light works when i unplug the relay and jump R/Y x BL/BK
3) HL, spedo and tach light works when i jump from battery + to W on relay plug. relay clicks, all stay on until ignition is killed.

Wiring diagram shows that W wire comes from the alternator... would the fact that the bike is not running change any of this? (waiting on a few more carb parts before i can start it)
Thanks for your time.

(81' xs1100sh)

You might have a bad diode but if you're trying to get the lights to work without the engine running, you can't do it.

The engine has to be running and the alternator has to working to turn on the headlight relay and the lights, just turning on the ignition won't work it unless someone's been into the wiring.

I got rid of the relay and put in a jumper, no more diode or relay problem.

[MaximPhil]

Hi SNDSLGR,
If all original parts in place. Headlight only comes on after bike starts. Something about a latching relay.
Wait for 3Phase if you want to know How it works.

Phil