Headlight Question

[bikerphil]

There is also a headlight relay that can go bad, it is also under the tank in front just above the ign. coils. If you have no voltage at the headlight connector, I would bypass the relay by unplugging it and jumping the red/yel and blu/blk wires. The headlight then should have power by turning on the key. GL

[jpilk99]

Is there a way to "check" if the RLU is not working - other than the headlight not working?

Just want to know that I'm smartly testing things to find the root cause. Thanks

Jay

[natemoen]

Is there a way to "check" if the RLU is not working - other than the headlight not working?

Just want to know that I'm smartly testing things to find the root cause. Thanks

Jay

Start by checking the bulb. Is there continuity between high beam and ground, and then low beam and ground, but not between high beam and low beam? Then the bulb is good.

When you have the bulb out check and see that there is voltage at the bulb socket.

[3Phase]

Jay,

It's not likely that the RLU is bad, it's a pretty simple and durable little device.

First, check the headlight itself, then try bypassing the Headlight Relay:

If the headlight is good, find and remove the Headlight Relay. It's under the fuel tank and almost directly above the ignition coils.

Put a jumper between the terminals in the Headlight Relay connector with the Blue/Black wire and the Red/Yellow wire. The headlight should come on when you turn on the Ignition switch.

The Headlight Relay can and does fail. If bypassing the relay allows the headlight to work you can leave it bypassed or replace the relay.


If that doesn't work:

You have a 1980 Midnight Special?

There's a diode in the wiring harness that feeds half-wave rectified 12 Volts DC to the Headlight Relay from one of the three alternator stator White wires. It can and does fail but it can be replaced. On my '80G the diode is on the middle of the three White wires at the Regulator/Rectifier connector and it's located along the right-hand side of the frame inside the wiring harness just aft of the Headlight Relay.

There are a few wiring harness connectors and the headlight High/Low switch between the RLU and the headlight. The connectors, switch terminals and solder points can break or get dirty and fail. Try bypassing the Headlight Relay first before you tear into the wiring harness and the left-hand handlebar switch. It'll all still need to be carefully taken apart, cleaned and reassembled but leave it alone until you try bypassing the relay.

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[jpilk99]

Scott,

That's an awesome post - thank you. I have a 1981 XS11 Midnight Special. Does that change much of your recommended course of action?

What is the "code name" of my bike? L, LG?

Thanks,

Jay

[BA80]

The 81 Midnight is an LH.

I have the relay bypassed on my 80 Special. As far as I'm concerned the relay is just something else to go wrong. If you keep your battery up it's moot.

[3Phase]

Jay,

I don't suppose you've been trying to make the headlight work with the engine off, have you? The Headlight Relay doesn't kick on and fire up the headlight until the engine is running and the alternator starts making power. If the engine's not running -- no headlight.


+1 on leaving the relay bypassed though. If a few amps make a difference between starting or not starting the engine there's something wrong and you need to find out what it is before you get stuck somewhere, uh, inconvenient with a dead bike.

Normally the HEAD failure indicator light glows just a little bit after the enigne starts to let you know it's working. I wasn't paying attention one day and the headlight relay or the diode failed while I was riding and I wound up going for half a day with no headlight. I did finally notice it when it started to get dark.

The relay's been bypassed now so that's two things things, the relay and the diode, that I don't have to worry about any more.

.

[Dux]

Relay Specs

3phase (or anyone), do you happen to know the specs for the relay and where to acquire one?

[3Phase]

XS11 Headlight Relays

3phase (or anyone), do you happen to know the specs for the relay and where to acquire one?

Dux,

There are two types of Headlight relays for the XS1100. You should have the 1980/81 relay. If the relay is bad and you want to get another relay you should send a PM to forum member andreashweiss and ask if him he has a late-model XS11 relay, or you can check eBay listings. I believe Andreas is a better choice.


Here is a small GIF sub-schematic for the 1980/81 Headlight relay wiring and a few pictures so you can get an idea of the physical differences between the early and late-model relays:

1980 and 1981 Yamaha XS1100 Headlight Relay and wiring harness connector diagram.

Models:
1980 XS1100 G Standard, SG Special, LG Midnight Special.
1981 XS1100 H Standard/Venturer, SH Special, LH Midnight Special.

-------->

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XS1100 headlight relays with the covers removed.

On the left is a 1980/81 relay and on the right is a 1978/79 relay.

The 1980/81 relay has an internal latch diode on the coil and the 1978/79 relay does not.





.
On the left is a 1980/81 relay and on the right is a 1978/79 relay.

The 1980/81 relay is smaller than the 1978/79 relay and the pinout is different.




.

[Dux]

wow, thanks 3phase!

[3Phase]

You're wlecome, Dux!

To keep the headlight relay pinouts and pictures sort of loosely grouped in the same thread.

The early model relay pinouts are different than the late-models along with the mount/orientation of the relays. The electrical connectors themselves for 1978-1981 are all pretty much the same so the relays will physically plug into the wrong year/model connector but they won't work.


1978 and '79 XS1100 E/F/SF Headlight relay and wiring.

Clockwise from the left:

Yellow = relay coil input ~7V AC from the alternator stator wye center-tap

Blue/Black = +12V DC 10A output to the RLU (Reserve Lighting Device)

Black = relay coil ground

Red/Yellow = +12V DC 10A input from the Headlight fuse




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[justme1100]

So, how well does that LED headlight light up the road?

[IanDMacDonald]

It works as well as a HID in my opinion. It really does it's work on bright. Eventually I'll get back out there and re-adjust it.

[Dux]

So, my issue was a little different. Frequently, when the bike would idle down the headlight and instrument lights would go very dim. sometimes by revving the bike a couple times they would come back to full brightness. I thought that this was a bike wide system voltage problem, but i checked and only the headlight and instrument lights were getting the low volts.

It seems what was happening was that when the rpms would fall to idle, the volts to the relay would drop and it would start to buzz (open and close really fast) resulting in very dim head an instrument lights (signals and brakes still at full intensity). Often revving the engine it woudl keep buzzing even when the output volts were 13.5v+ . Using a jumper in place of the relay I get full intensity headlight and instrument lights no matter what.

I took the relay apart and the insides look pristine (it IS the new style and has an internal diode). There is also a diode (I think the PO) wired in leading to relay, if I remove it or reverse it = no lights, if i replace it with a jumper, i get the original behavior (intermittent relay buzzing and dim lights).

Finally, after just replacing the relay with a jumper across the the Blue/Black wire and the Red/Yellow wire, I went for a long ride and had full intensity instrument and headlights for the entire ride. So I'm still not sure if i have a bad diode(s) or bad relay, or something else... (my peak output voltage @~3500 rpm is ~ 13.5v). But with the jumper, I get full bright lights, so it's "fixed" for now :/

Now the crux...
During the ride, my turn signals quit working. There seems to be very low (~9v) voltage at the signal relay. I think whilst fiddling with the headlight relay and diode, I must have disturbed a loose connection somewhere within the wrapped harness under the tank. By moving the wrapped harness a little and re-cleaning (with de-oxit) all the connectors under the tank, the turn signals are now reliable again, but i'm still only getting about 10v to the signal relay.

I have metered every connection i can find between the battery and signal relay and the only remaining locations for the voltage drop (intermittent ~3v, and constant ~1.5v) are the wrapped harness and the ignition switch.

Is the a post somewhere detailing how to remove, disassemble and clean the ignition switch? I'd like to do that before i start taking apart the harness...

Sorry for the long post

[3Phase]

How's it going, Dux? Do you have a manual and/or a schematic?

1980 XS1100SG/LG and 1981 XS1100SH/LH Color Schematic

So, my issue was a little different. Frequently, when the bike would idle down the headlight and instrument lights would go very dim. sometimes by revving the bike a couple times they would come back to full brightness. I thought that this was a bike wide system voltage problem, but i checked and only the headlight and instrument lights were getting the low volts.

It seems what was happening was that when the rpms would fall to idle, the volts to the relay would drop and it would start to buzz (open and close really fast) resulting in very dim head an instrument lights (signals and brakes still at full intensity). Often revving the engine it woudl keep buzzing even when the output volts were 13.5v+ . Using a jumper in place of the relay I get full intensity headlight and instrument lights no matter what.

With the Ignition Switch OFF and the Engine OFF:

Check the Battery voltage and make sure it's greater than 12.6 volts.


With the Ignition Switch ON and the Engine OFF:

Check the Battery voltage again to make sure it's still greater than 12.6 volts and not dropping too quickly with the basic pre-start electrical load.

Check the voltage on ALL of the Brown wires at the Input/Line side of the Fuse Block. The Brown wires are the 12 volt switched power feed from the Brown wire at the Ignition Switch. They're all spliced onto the Brown wire inside the wiring harness just upstream of the Fuse Block so they should ALL be within a half a volt of the Battery voltage.

Check the voltage at the Output/Load side of each fuse in the Fuse Block. Again, they should ALL be within a half a volt of the Battery voltage. If there's a larger voltage drop or it fluctuates while you're measuring the voltage then the fuse itself or one of the fuse holder connectors is dirty/bad.

Check the voltage on the Red/Yellow wire up at the Headlight Relay connector. For any model of 1980 or 1981 XS1100 there is nothing on the Red/Yellow wire between Headlight fuse and the Headlight Relay connector so the voltage should be identical to the voltage measured at the Headlight fuse.

I took the relay apart and the insides look pristine (it IS the new style and has an internal diode). There is also a diode (I think the PO) wired in leading to relay, if I remove it or reverse it = no lights, if i replace it with a jumper, i get the original behavior (intermittent relay buzzing and dim lights).

Finally, after just replacing the relay with a jumper across the the Blue/Black wire and the Red/Yellow wire, I went for a long ride and had full intensity instrument and headlights for the entire ride. So I'm still not sure if i have a bad diode(s) or bad relay, or something else... (my peak output voltage @~3500 rpm is ~ 13.5v). But with the jumper, I get full bright lights, so it's "fixed" for now :/

With the Ignition Switch ON and the Engine OFF:

At the Headlight Relay, briefly jumper the Red/Yellow wire to the White wire. The relay should click once to turn on the headlight and the headlight should stay on after you remove the jumper.

If the relay doesn't turn on at all it's a bad relay.

If the relay turns on but won't stay latched when you remove the jumper, disconnect the diode in the wiring harness (or unplug the 6-pole Alternator connector behind the Fuse Block) and try again. If the diode in the wiring harness is shorted it will backfeed 12 volts into the Alternator Stator windings and that can put a heavy load on the White wire. With the engine off and the alternator not doing any useful work there may not be enough current supplied through the latching diode to the White wire to keep the Headlight Relay coil energized.

Now the crux...
During the ride, my turn signals quit working. There seems to be very low (~9v) voltage at the signal relay. I think whilst fiddling with the headlight relay and diode, I must have disturbed a loose connection somewhere within the wrapped harness under the tank. By moving the wrapped harness a little and re-cleaning (with de-oxit) all the connectors under the tank, the turn signals are now reliable again, but i'm still only getting about 10v to the signal relay.

I have metered every connection i can find between the battery and signal relay and the only remaining locations for the voltage drop (intermittent ~3v, and constant ~1.5v) are the wrapped harness and the ignition switch.

Is the a post somewhere detailing how to remove, disassemble and clean the ignition switch? I'd like to do that before i start taking apart the harness...

Sorry for the long post

From your description, the most likely problem is dirty Turn Signal connectors and/or switch terminals. If you measured the voltage at the Brown wires in the Fuse Block and they were within a half a volt of the Battery voltage you don't need to worry about the Ignition Switch right now. If it's working just leave it alone, you can take it apart and clean the switch and its connector after you fix the Signals.

There are not very many Turn Signal splices inside the wiring harness and they're not likely to go bad unless the harness was misrouted and it got pinched by the triple tree, you set the fuel tank on it, or you took the harness off the bike and played Tarzan/Indiana Jones with it.

With the Ignition Switch ON and the Engine OFF:

On the left-hand handlebar, push the Turn Signal Switch lever straight in and then release it to make sure the switch is mechanically centered internally. The Signals do sometimes appear to have a life and mind of their own but there is no way to test them to ensure that they are Spiritually centered internally.

When the Turn Signal Switch is mechanically centered internally, check the voltage at the Brown wire on the Turn Signal Flasher Relay. The Brown wire comes directly from the 20 amp Signal fuse so it should be within a half a volt of the Battery voltage.

At this time, don't worry about making any voltage measurements on the other two relay terminals. If there is roughly Battery voltage at the relay Brown wire then you have some work to do before any voltage readings at the other terminals will be reliable.


With the Ignition Switch OFF:

Make sure the Turn Signal bulbs are the correct type and don't laugh. The Signal circuit is designed to work with a 27 watt element in the front and rear bulbs plus the 1 or 2 watts in the Indicator bulb for about a 55 or 56 watt load per side. If the wrong bulbs are used then the Signals may not work at all.

Clean the Turn Signal lamp sockets. Unless you are absolutely sure that the sockets and pins are all clean and correctly grounded you could be chasing gremlins for days/decades.

Clean all of the terminals and firmly seat the two wiring harness connectors for the left-hand handlebar switch.

Carefully! disassemble and clean all of the switch terminals in the left-hand handlebar switch. If a solder joint breaks it was already bad, trust me.

Solder any broken joints back together, clean and lightly grease all of the switch terminals with dielectric grease and carefully! reassemble the switch.

Make sure the Black wire is connected to its ground screw and the switch assembly itself has a good ground through handlebar to the frame or the Signal circuit won't work correctly.

Sorry for the long Reply!

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