High Voltage Running to Headlight

[tusticles]

Hi everyone, I've got a 1978 xs750se and after replacing a bad regulator rectifier with a ESR310 from electrosport.com**, I noticed the headlight stopped working. I put a multimeter in the connectors of the headlamp wiring plug and both low beam and high beam are registering 16-17 volts at idle and upwards of 28-30volts when throttle is given. I imagine that this blew the headlight. All the other lights, turn signals function properly still. Think this could be a bad (new) regulator rectifier or there's a wiring issue somewhere along the way?

 

Thanks for your help! It's brutal not riding because of not having a functioning headlight. I've contacted electrosport to inquire about the issue and a possible bad RR but would love your input as well. Thanks.

Edited January 10, 2019 by tusticles

[BlueSky]

Check your meter with a known source such as a 12 volt battery. If the meter is correct the new R/R is bad.

[tusticles]

The meter appears to be functioning correctly. Reading 12.6 volts on the battery. Thanks BlueSky! Good validation in the bad R/R

[Flyinfool]

What does the meter show across the battery with the engine running. You should never get high voltage to only one place, You are subjecting everything on the bike to that same voltage and it will shorten the life of everything.

It is possible that you wired something incorrectly to have the RR not doing its job, but it is also not unheard of to have a brand new bad part.

[tusticles]

What does the meter show across the battery with the engine running. You should never get high voltage to only one place, You are subjecting everything on the bike to that same voltage and it will shorten the life of everything.

It is possible that you wired something incorrectly to have the RR not doing its job, but it is also not unheard of to have a brand new bad part.

 

At idle the battery reads 12.7 and with throttle it doesn't go above 14. stays around 13.8 - 13.9 volts.

[Du-Rron]

Hi everyone, I've got a 1978 xs750se and after replacing a bad regulator rectifier with a ESR310 from electrosport.com**, I noticed the headlight stopped working. I put a multimeter in the connectors of the headlamp wiring plug and both low beam and high beam are registering 16-17 volts at idle and upwards of 28-30volts when throttle is given. I imagine that this blew the headlight. All the other lights, turn signals function properly still. Think this could be a bad (new) regulator rectifier or there's a wiring issue somewhere along the way?

 

Thanks for your help! It's brutal not riding because of not having a functioning headlight. I've contacted electrosport to inquire about the issue and a possible bad RR but would love your input as well. Thanks.

 

Is this AC volts at the headlight?

[tusticles]

Is this AC volts at the headlight?

 

DC Volts

[Flyinfool]

At idle the battery reads 12.7 and with throttle it doesn't go above 14. stays around 13.8 - 13.9 volts.

 

That voltage at the battery is exactly correct to what it should be.

 

That really does not sound right. All the power on the bike goes thru the main fuse. You should have the same voltage everywhere on the bike. By chance did you recheck the voltage at the headlight at the same time as you were getting the battery readings. The only thing I can think of offhand is that you have an intermittent RR that was not working when you tested the headlight but was working when you tested at the battery.

 

More pondering required........

[tusticles]

That voltage at the battery is exactly correct to what it should be.

 

That really does not sound right. All the power on the bike goes thru the main fuse. You should have the same voltage everywhere on the bike. By chance did you recheck the voltage at the headlight at the same time as you were getting the battery readings. The only thing I can think of offhand is that you have an intermittent RR that was not working when you tested the headlight but was working when you tested at the battery.

 

More pondering required........

 

I did not recheck the voltage at the headlight at the same as I was getting the battery readings. I can do that. It's definitely requiring some good pondering.

 

The last thing that the ElectroSport sales manager said was "You have to have either A) a bad reg/rect combine with a flaw in the wiring, or B) just a flaw in the wiring. Your problem also seem to be intermittent, which is not typical of regulator failures. Once the regulation circuit in the unit goes out its just dead from that point on all the time. Your unit seems to be successfully regulating now during the recent test, makes me think something is wrong beyond the reg/rect. The headlight should be getting power from the battery, there should only be one voltage for the entire bike's electrical system because all the power is within one shared circuit. Where does your headlight get power, because if its voltage is not equal to the battery then that power is not coming from the battery."

[Flyinfool]

That is kind of what I was saying.

Yes you need to do another test please. My poor brain is hurting.

[Patch]

So what everyone here is sayin is exactly right but there's a couple of us and Puc likely knows this one as well?

Some time we cheat for the coils, this makes for an off road only but... what this does is exploit the X factor on the primary and secondary's

If the PO (s) chose to do this cheat for the coils then likely he hid the patch through the harness? At least I would.

If it were me I would expose the harness and disconnect each plug looking for anything out of normal, with the key on check voltage and grounds on each terminal. Always recheck battery voltage during procedures for changes in voltage, this gives you a clearer picture of gains or loses.

It is possible that a patch has short to the head lamp wire. Or just run a new wire to the lamp.

[tusticles]

So what everyone here is sayin is exactly right but there's a couple of us and Puc likely knows this one as well?

Some time we cheat for the coils, this makes for an off road only but... what this does is exploit the X factor on the primary and secondary's

If the PO (s) chose to do this cheat for the coils then likely he hid the patch through the harness? At least I would.

If it were me I would expose the harness and disconnect each plug looking for anything out of normal, with the key on check voltage and grounds on each terminal. Always recheck battery voltage during procedures for changes in voltage, this gives you a clearer picture of gains or loses.

It is possible that a patch has short to the head lamp wire. Or just run a new wire to the lamp.

 

I could see a PO re-wiring something if needed. Are you familiar with where the head lamp wire is ran to? I can't seem to locate the Reserve Lighting Unit on this bike.

 

That is kind of what I was saying.

Yes you need to do another test please. My poor brain is hurting.

 

 

Alright, so I just got the bike to my wood shop for a nice flat quiet place w/ tools to test more. On the way here, the lowbeam workedfor 98% of the trip! When I parked, with the engine still running, the light was off. I gave it throttle but it remained unlit. I also, for the first time to my notice, saw the "Head Lamp" light on the dashboard lit up.

 

I brought it inside and re-did some voltage tests to the headlight hi/low AND retest the battery voltage both at idle and throttle, and these are the results

 

Battery :

- idle - 12.92

- throttle - 14.2

 

Headlight : *Results are respective to whether hi/low beam switch was engaged.

Low Beam :

- idle - 13

- throttle - 40

Hi Beam :

- idle - 14

- throttle - 45

 

Still head scratching, especially that I just experience the headlight working. The battery, with throttle reaching voltage over 14 is alarming, yes?

 

 

 

 

[Patch]

I could see a PO re-wiring something if needed. Are you familiar with where the head lamp wire is ran to? I can't seem to locate the Reserve Lighting Unit on this bike.

 

 

 

 

Alright, so I just got the bike to my wood shop for a nice flat quiet place w/ tools to test more. On the way here, the lowbeam workedfor 98% of the trip! When I parked, with the engine still running, the light was off. I gave it throttle but it remained unlit. I also, for the first time to my notice, saw the "Head Lamp" light on the dashboard lit up.

 

I brought it inside and re-did some voltage tests to the headlight hi/low AND retest the battery voltage both at idle and throttle, and these are the results

 

Battery :

- idle - 12.92

- throttle - 14.2

 

Headlight : *Results are respective to whether hi/low beam switch was engaged.

Low Beam :

-

idle - 13 This is as should be, reading battery voltage

-

throttle - 40 This is off your stator!

Hi Beam :

- idle - 14

- throttle -

45 Same here

 

Still head scratching, especially that I just experience the headlight working. The battery, with throttle reaching voltage over 14 is alarming, yes?

 

 

 

 

So what i think is confusing you is that YOU THINK you are reading proper battery voltage at the lamp but I don't believe you are!

 

Leaving aside the cheat I mentioned//// this circuit is shorted to the bikes charging system!?

 

One thing I would like to know, likely others too, is the ign. coil voltage reading with rpm at the coils terminals? This will tell us if there's the cheat at play!

 

Next thing is assuming you have the wiring diagram follow that circuit, you can also post the diagram used so we can play along with you.

 

With or without the diagram what you should do is open the main harness by carefully removing the shielding tape and closely examine each wire for ripples or signs of excessive heating. Then follow the wire from the headlamp back thru the harness and to the fuse (what is the voltage at the fuse?) this may point you/us in a direction. High voltage at the fuse suggests the short is before the fuse block or potentially inline fuse! Regular volts reading at lamp fuse indicates short after fuse block!

 

Remember bike has to be running and with charging rpms!!!!!!!!!!

 

Let the club know whats the results are. I starting Monday am busy for a couple days but many members will be at their keyboards.

Edited January 13, 2019 by Patch

[Patch]

Certainly see I am out of post practice...my French really showing thru! Well I cleaned it up some hope it makes more sense.

[tusticles]

Next thing is assuming you have the wiring diagram follow that circuit, you can also post the diagram used so we can play along with you.

 

Here's what I've been using off a google search. Unfortunately, I don't have an official one, nor seem to be able to find one for 78' xs750se. You're able to find the one that I'm using if this is poor quality for you by googling "1978 xs750se wiring diagram" and clicking images. It's the second one as the first one is for an 850 I believe.

[Patch]

Wow at 1st glance this looks like a an underground/map of Jeff's basement plumbing;)

 

I'm going thu it but as mentioned follow the wire back from the headlight through the opened harness.

[tusticles]

REST ASSURED EVERYONE... I found a loose fuse connection. Old fusebox connections are weak so the fuse wasn't tight. Explained why it worked earlier and then not again.

 

Still going to buy a new headlamp, because the hi beam is burnt, but will see what happens with that as well.

 

Thanks everyone for your help. Gosh, I feel real silly.

[Patch]

REST ASSURED EVERYONE... I found a loose fuse connection. Old fusebox connections are weak so the fuse wasn't tight. Explained why it worked earlier and then not again.

 

Still going to buy a new headlamp, because the hi beam is burnt, but will see what happens with that as well.

 

Thanks everyone for your help. Gosh, I feel real silly.

 

 

Are you saying the high voltage is gone?

[Patch]

Like a bone chasing a dog I found this schematic.

I am assuming the red wire trace I show is the problem.

But also to be done with it I personally would open and clean the ing. switch.

Also while you're at it inspect the ground as marked on the bottom center of schematic. labeled black at the frame connection/termination -

Yellow trace is fuse box power source?? so an easy box to just swap out.

 

Cheers

[tusticles]

Like a bone chasing a dog I found this schematic.

I am assuming the red wire trace I show is the problem.

But also to be done with it I personally would open and clean the ing. switch.

Also while you're at it inspect the ground as marked on the bottom center of schematic. labeled black at the frame connection/termination -

Yellow trace is fuse box power source?? so an easy box to just swap out.

 

Cheers

 

Wow! Thanks Steven. I greatly appreciate you taking the time to look over that and map it out. It's a rainy day today and tomorrow here in San Diego so I'll look in to those Tuesday afternoon or Wednesday and report back what I find with either corrosion or wire quality level.

[Patch]

A couple of thoughts for you to keep in mind when you get back at it.

 

What you will be attempting is best described as chasing ghosts; the reason is that you may find one obvious fail, get distracted by it, believe you’ve solved the problem but, more often than not on a 40 year old harness there’s a lot more going wrong then obvious.

 

DuRon and Jeff are on to the same issue, and they are both right. But because you are sure its DC volts then safe to assume the rectifier is working!? The regulator seems to be hit and miss.

 

Getting back to the front lamp circuit, if it has more than battery voltage metered at the head lamp then it has the same throughout that circuit green & yellow wires! There can be an exception to this only but if the factory harness has been altered then it is possible to have more voltage pertaining to one end of a circuit verse the other end. Example a broken green or yellow wire somewhere before the front lamp but still good further back so, one might just run a separate feed to the front lamp say from the relay and allow the rest of the circuit (flashers, tail light…) to be left as is!

 

Opening the harness is common on old bikes. Cleaning every harness connector, switch and ground is in most cases a necessity.

 

Not much information on your bike but I did read stator outputs from 30 to 50 volts.

 

The rectifier & regulator or RR: The circuit I trace is the RR, the stator feeds it,(skipping over exciter..) when you turn the key on you feed battery voltage to the RR, the RR MUST see an accurate voltage, this means a clean zero volt loss, in other words true battery voltage! This on an old system is a lot to expect, so, every contact point must be cleaned and this includes harness connectors!

Also this RR needs to switch open/closed constantly, it does so thru the ground/earth and again this ground MUST be checked for impedance. These are the connectors I circled in green at the RR, so if you read no voltage loss there, you may be able to skip the ing. Switch cleaning; same for the ground check it there for impedance.

 

Anyways checking the complete harness is the best way to get the bike to be more reliable.