my try at repairing headlight relay in junction box - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 33 (permalink) Old 12-14-2012, 12:03 AM Thread Starter
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my try at repairing headlight relay in junction box

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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post #2 of 33 (permalink) Old 12-14-2012, 07:38 AM
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'86 VN750 13,700 mi -Stock
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post #3 of 33 (permalink) Old 12-14-2012, 09:25 AM
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Quote:
Originally Posted by new rider 9984 View Post
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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post #4 of 33 (permalink) Old 12-14-2012, 09:52 AM
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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/data.../EP2-B3N3S.pdf

Scroll down to the MR301 series.........
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post #5 of 33 (permalink) Old 12-14-2012, 11:56 AM Thread Starter
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Quote:
Originally Posted by dariv View Post
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/data.../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

Quote:
Originally Posted by denny6006 View Post
Sucks getting old but it beats not getting old.

i got my helmet but it sure makes licking the windows a chore

cell phone number for anyone who needs it 214-516-1738

photobucket link
http://s1066.photobucket.com/user/newrider9984/library/
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post #6 of 33 (permalink) Old 12-14-2012, 04:50 PM
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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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post #7 of 33 (permalink) Old 12-14-2012, 05:07 PM
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Quote:
Originally Posted by Mercury View Post
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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post #8 of 33 (permalink) Old 12-14-2012, 06:25 PM
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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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post #9 of 33 (permalink) Old 12-14-2012, 11:48 PM
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Quote:
Originally Posted by kc2dgq View Post
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"

Quote:
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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post #10 of 33 (permalink) Old 12-15-2012, 01:10 AM
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Gods, I love it when geeks come together !!! 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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