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ass hole extaordinaire
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It seems to be a common issue on our vn750's that the headlight relay fails.
Up until now there was only two ways to remedy this. It was either cough up the cash and buy another used one at a ridiculous price (or for the millionaires among us you could always buy a new one) or you would have to do the relay bypass mod which makes the headlight illuminate when you turn the key on.

I am a firm believer in the bypass as I have used it myself, however, I feel it has to be putting a strain on the other electrical components during start up.

So I have decided to dive into the junction box and see what kind of mess I can make.

So far I have opened the box and tested to see which relay is which and i have found that they are not correctly placed in the diagram found in the manual.

I went out to the bike and plugged the JB board into it.
With one hand on the relays I started the bike and felt for the click telling me which relay was the starter relay. Then I grounded out the fan switch and felt for that click. With two relay positions confirmed then it only leaves the third for the headlight. I started the bike and the headlight stayed off verifying that the headlight relay was indeed faulty.

I unplugged the JB and unsoldered the headlight and the fan relay.
Then I switched there positions and resoldered them in their new places.

Back out at the bike I attached the experimental JB and started the bike.
The starter worked and the headlight illuminated.
Just for fun I grounded out the fan switch and the fan did not work.

Guaranteed relay failure.

Now buying a new relay is out of the question due to the company discontinuing that particular one. So I did some searching to see if i could find a compatible relay and I believe I have found one.
As soon as they arrive in the mail the testing will resume.

Until then here are pics of the JB circuit board.





 

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..have a vulcan good day!
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VERY Elementary Circuity !

:smiley_th
 

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It seems to be a common issue on our vn750's that the headlight relay fails.
Up until now there was only two ways to remedy this. It was either cough up the cash and buy another used one at a ridiculous price (or for the millionaires among us you could always buy a new one) or you would have to do the relay bypass mod which makes the headlight illuminate when you turn the key on.

I am a firm believer in the bypass as I have used it myself, however, I feel it has to be putting a strain on the other electrical components during start up.

So I have decided to dive into the junction box and see what kind of mess I can make.

So far I have opened the box and tested to see which relay is which and i have found that they are not correctly placed in the diagram found in the manual.

I went out to the bike and plugged the JB board into it.
With one hand on the relays I started the bike and felt for the click telling me which relay was the starter relay. Then I grounded out the fan switch and felt for that click. With two relay positions confirmed then it only leaves the third for the headlight. I started the bike and the headlight stayed off verifying that the headlight relay was indeed faulty.

I unplugged the JB and unsoldered the headlight and the fan relay.
Then I switched there positions and resoldered them in their new places.

Back out at the bike I attached the experimental JB and started the bike.
The starter worked and the headlight illuminated.
Just for fun I grounded out the fan switch and the fan did not work.

Guaranteed relay failure.

Now buying a new relay is out of the question due to the company discontinuing that particular one. So I did some searching to see if i could find a compatible relay and I believe I have found one.
As soon as they arrive in the mail the testing will resume.

Until then here are pics of the JB circuit board.





Great post. I would also check those solder joints for solder fractures, it seems common on heavier items (relays / fuse holders). Just look at the solder joint real close and jiggle said relay - if you see the joint move at all, resolder it. From the pictures it looks like some of those joints can use more solder to me. When they (if they) wave flowed that board sometimes you dont get enough solder on the pin / pad - especially with it being a 1 sided board.

good luck

kenny
 

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It's a ma kaw special relay.... NEC MR301-N9 (denoted by the 'N')
Best direct fit replacement is the NEC MR301-12HSL
A little hard to find, but they can be had for under $20
Very easy replacement for anyone who can use a soldering iron.
I'm going to try to find a better solid state replacement.........
Here is the data sheet for the NEC:
http://www.datasheetcatalog.org/datasheet/nec/EP2-B3N3S.pdf

Scroll down to the MR301 series.........
 

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ass hole extaordinaire
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3,780 Posts
Discussion Starter #5
It's a ma kaw special relay.... NEC MR301-N9 (denoted by the 'N')
Best direct fit replacement is the NEC MR301-12HSL
A little hard to find, but they can be had for under $20
Very easy replacement for anyone who can use a soldering iron.
I'm going to try to find a better solid state replacement.........
Here is the data sheet for the NEC:
http://www.datasheetcatalog.org/datasheet/nec/EP2-B3N3S.pdf

Scroll down to the MR301 series.........
thats not the one i have ordered the ones i got were listed on ebay five for $10
 

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Dariv - how often do these fail that you want to go solid state?

I suggest a hex fet - we use the IRF 530 - its a great part. Make sure you filter the living heck out of the power though - engine alternators are usually noisy as heck (electrically).

Kenny
 

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Dariv - how often do these fail that you want to go solid state?

I suggest a hex fet - we use the IRF 530 - its a great part. Make sure you filter the living heck out of the power though - engine alternators are usually noisy as heck (electrically).

Kenny
The headlight relay failure seems to be very common.... seems like every few months or so someone has a headlight problem. My concern is that replacing the relay with another similar relay will only fail again in time. Bad circuit design or someone spec'ed a relay that wasn't up to the task.... I wont know till I examine a JB.... Hense, the idea of going to solid state...
 

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how easy is it to get the board out of the JB housing...can you put it back together and still have it look like a factory issued one?

Can you take the cover off the relay itself? maybe just cleaning the contacts if the coil is still good. what other components are in the actual relay housing? Diodes to prevent contact bounce? latching circuit?

and finally....where are the diodes located in the JB and can you get a number off of them?
 

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Can you take the cover off the relay itself? maybe just cleaning the contacts if the coil is still good.
Sounds like when it goes bad it doesn't energize anymore... so not really a "dirty contact"

and finally....where are the diodes located in the JB and can you get a number off of them?
looks like they are on the left side under the lines coming into the JB....
 

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Gods, I love it when geeks come together !!! :smiley_th im REALLY diggin what you guys are doin....and hey, from a fossil....I used to build Hallicrafter type radios and such...why not just design a VN specific board from scratch bypassing the known problems....or am I outta my league here ?...tell me, I wont be offended...

I got the tools, the know how, just that the eyes are shot now....
 

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ass hole extaordinaire
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3,780 Posts
Discussion Starter #11
how easy is it to get the board out of the JB housing...can you put it back together and still have it look like a factory issued one?

Can you take the cover off the relay itself? maybe just cleaning the contacts if the coil is still good. what other components are in the actual relay housing? Diodes to prevent contact bounce? latching circuit?

and finally....where are the diodes located in the JB and can you get a number off of them?
answers in sequence
easy and yes
relay is sealed
no numbers on diodes five diodes in total all under the runs coming off the ten pin
 

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ass hole extaordinaire
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Discussion Starter #12
The headlight relay failure seems to be very common.... seems like every few months or so someone has a headlight problem. My concern is that replacing the relay with another similar relay will only fail again in time. Bad circuit design or someone spec'ed a relay that wasn't up to the task.... I wont know till I examine a JB.... Hense, the idea of going to solid state...
i am going with a direct fit same size and shape relay but it can handle way more power
 

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ass hole extaordinaire
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Discussion Starter #13
Gods, I love it when geeks come together !!! :smiley_th im REALLY diggin what you guys are doin....and hey, from a fossil....I used to build Hallicrafter type radios and such...why not just design a VN specific board from scratch bypassing the known problems....or am I outta my league here ?...tell me, I wont be offended...

I got the tools, the know how, just that the eyes are shot now....
havent heard of any other major issues with the JB so far

i am hoping to market my labor on this as a permanent yet cost efficient fix
 

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Gods, I love it when geeks come together !!! :smiley_th im REALLY diggin what you guys are doin....and hey, from a fossil....I used to build Hallicrafter type radios and such...why not just design a VN specific board from scratch bypassing the known problems....or am I outta my league here ?...tell me, I wont be offended...

I got the tools, the know how, just that the eyes are shot now....
If I get my hands on a junked unit.....I was going to make an add-on board to accommodate replacement of the relay......or a total re-design of the JB.
Making an etched PC board from scratch at home with little cost is not difficult if you have the know how.
 

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Gods, I love it when geeks come together !!! :smiley_th im REALLY diggin what you guys are doin....and hey, from a fossil....I used to build Hallicrafter type radios and such...why not just design a VN specific board from scratch bypassing the known problems....or am I outta my league here ?...tell me, I wont be offended...

I got the tools, the know how, just that the eyes are shot now....
If I get my hands on a junked unit.....I was going to make an add-on board to accommodate replacement of the relay......or a total re-design of the JB.
Making an etched PC board from scratch at home with little cost is not difficult if you have the know how.
This is the direction I was going in. The JB has flaws....we know that....
So why not go with replaceable relays, additional circuits for lights, air horn, and such.... KC, we should get together on this one and design a replacement. I had no plan to sell these for anything more than cost thou.... so you would have to be cool with doing it "pro bono"
 

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Hey all...

1. One needs to make sure that the relay is not energizing due to the fact of a intermittant solder joint - at least reflow everything and make sure that was not the culprit.

2. I have seen a funny thing with relays over the last couple years, a phenomenon called transfer of material. The contact surface when switched on actually transfers some contact surface material to the other contact, enough material transferred and you get one contact with a valley and another with a point, eventually the contact 'sticks' on - I do not know if that is happeneing here but....

3. If you want to check for transfer of material or to look inside the relay, I have done this, cut the top of the relay off using a razor knife - a new one, cut around the outside edge of the whole top, you should then be able to see the coil side and the contact side, and if you energize / de-energize you should be able to see what the issue is.

4. If the relay stops 'energizing' has anybody checked to see if the coil is open? Throw an ohm meter on there.

Thats all I got.

Kenny
 

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Hey all...

1. One needs to make sure that the relay is not energizing due to the fact of a intermittant solder joint - at least reflow everything and make sure that was not the culprit.

2. I have seen a funny thing with relays over the last couple years, a phenomenon called transfer of material. The contact surface when switched on actually transfers some contact surface material to the other contact, enough material transferred and you get one contact with a valley and another with a point, eventually the contact 'sticks' on - I do not know if that is happeneing here but....

3. If you want to check for transfer of material or to look inside the relay, I have done this, cut the top of the relay off using a razor knife - a new one, cut around the outside edge of the whole top, you should then be able to see the coil side and the contact side, and if you energize / de-energize you should be able to see what the issue is.

4. If the relay stops 'energizing' has anybody checked to see if the coil is open? Throw an ohm meter on there.

Thats all I got.

Kenny
I have secured a JB and am waiting for the mail. I intend to look into all these things and post pics of the relay innerds
 

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This is the direction I was going in. The JB has flaws....we know that....
So why not go with replaceable relays, additional circuits for lights, air horn, and such.... KC, we should get together on this one and design a replacement. I had no plan to sell these for anything more than cost thou.... so you would have to be cool with doing it "pro bono"
I have no problem with working with you on it Dariv.

I am not here to profit off other members. There is such little aftermarket stuff for this bike that I am just trying to help other members who are looking for inexpensive options to enjoy their bikes.
As some of you know, I do sell some items, but I am not making a huge profit on them. I only charge for material, time and just enough profit to get more materials.....my way of paying it forward.

PM me and we can work on it.
 
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