What is the Value of the resistor in the lighting circuit of an XS650D

Nelson

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What is the resistance and wattage of the resistor connected between the headlight high beam and the dimmer switch. I can't find the one I took off the bike when I started this project so need to replace it. The color coded schematic shows it connected with a yellow wire from the headlight high beam and a yellow/green wire from the resistor to the dimmer switch. I can't find any reference to it in any of the manuals I have much less what the resistance is or the power rating of the resistor. thanks for any info you can provide.
 
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What is the resistance and wattage of the resistor connected between the headlight high beam and the dimmer switch. I can't find the one I took off the bike when I started this project so need to replace it. The color coded schematic shows it connected with a yellow wire from the headlight high beam and a yellow/green wire from the resistor to the dimmer switch. I can't find any reference to it in any of the manuals I have much less what the resistance is or the power rating of the resistor. thanks for any info you can provide.
I can guess at the wattage since it will be the max wattage of the headlight, so using an LED H4 I have 15 watts. To give a bit of pad I could use a 20 watt resistor. The problem is I still need to know the resistance. If I take the maximum wattage of the low beam side I can probably calculate a resistance range which would work, but if anyone could throw an ohmmeter on the resistor and let me know what you find I would really appreciate it.
Thanks,
 
650 and 750 shared the same resistor. You gotta spend money either way... why not jus' buy the correct one...

https://www.ebay.com/itm/Genuine-Yamaha-1J7-81911-01-00-Resistor-Assembly-XS750-1977/163794983562

1715291087156.png
 
Jim, Part ordered and on the way. I appreciate your help!
When you receive the part, would you mind measuring its resistance and posting it here? For posterity. And to satisfy my electrician curiosity? :)
(I realize you cannot measure wattage but it can easily be calculated from the resistance and position in the circuit)
 
When you receive the part, would you mind measuring its resistance and posting it here? For posterity. And to satisfy my electrician curiosity? :)
(I realize you cannot measure wattage but it can easily be calculated from the resistance and position in the circuit)
Yes, I was planning to do that. I figure the wattage would have to be about the same as the high beam draws. I am using an LED H4 headlight so the resistor will be capable of handling more wattage than the LED will ever pull.:D
 
Thanks. I don't have a parts list and didn't know the part number. This is better than having to cauble something together. Again, Thanks for the info
No worries. Partzilla is really helpful for finding alternate sources. When you find your part in one of their diagrams, you can click on it and it takes you to the ordering page... pretty much the same as any parts place. What's different with Partzilla is there's also a cross reference on that page. In this case I found your part here...

1715354860796.png



Click on that part number and it takes you to the ordering page (it's NLA), but that page also lists what other bikes the part was used on. In this case, the '77 XS750. Partzilla also has it's fair share of mistakes too, so just to double check I'll go the the parts list for that bike and make sure it cross references back to my bike. If it does, it's a pretty good indication the two are compatible.


1715355277423.png
 
I figure the wattage would have to be about the same as the high beam draws.
Electrically, it would not actually need to be that high. When running more than 1 load in series, they reduce the current and thus their wattage plus they split the wattage (par their resistance).

As an example:
An H4 halogen high beam draws 5A @ 12V, making it consume and dissipate 60W. Voltage of 12V and current of 5A gives us 2.4 Ohm resistance.
If you put in another 2.4 Ohm resistor in series, the overall resistance will go up to 4.8 Ohm which will make the circuit draw only 2.5A @ 12V.
Now that the circuit draws half the amps (with no change in voltage), it consumes half the wattage. But since you also split the wattage across two equal load elements, they share the new 30W power at 50/50 ratio, making the headlight consume 15W and the resistor as well.
But that's just an example. Depending on the manufacturer's desire, the resistor might have higher or lower resistance to dim the high beam more or less.

So once you have that new resistor, publish its resistance value here (down to 1/10th of an ohm, if you can) and we'll calculate its power dissipation rating.
 
No worries. Partzilla is really helpful for finding alternate sources. When you find your part in one of their diagrams, you can click on it and it takes you to the ordering page... pretty much the same as any parts place. What's different with Partzilla is there's also a cross reference on that page. In this case I found your part here...

View attachment 325537


Click on that part number and it takes you to the ordering page (it's NLA), but that page also lists what other bikes the part was used on. In this case, the '77 XS750. Partzilla also has it's fair share of mistakes too, so just to double check I'll go the the parts list for that bike and make sure it cross references back to my bike. If it does, it's a pretty good indication the two are compatible.


View attachment 325540
I have used Partzilla in the past but couldn't remember the name. It's hell getting old. Part of the problem is I started this restoration/modification of my Yamaha XS650d/Velorex Sidecar outfit in 2007 after my wife asked me when I was going to get "her" sidecar outfit running (we also have a 05 Harley ultraclassic sidecar outfit). When she asked when I was going to get it running what I'm sure I heard was "get it running, I don't care what it costs" so needless to say I have spent much more than it will ever be worth but we took our honeymoon up to West Edmenton, Alberta from our home in Washington State so it has "sentimental value." It was her first experience with motorcycling and she has loved riding ever since. I had 15" automotive spoked rims laced to all three hubs so I can run car tires, Had a leading link front end custom built to reduce the trail, and installed dual discs on the front. I installed a big fin 750cc cylinder block, had the crank turned to an 83 degree offset and of course the cam cut and welded for the new timing. I have installed a high output alternator and a Pamco electronic ignition along with Mikes XS Green Monster coils. I have a nephew who owns a chrome shop in the Sacramento area and so I got over $2,000.00 worth of chrome plating for free :p. I had the frame of both the bike and the sidecar powder coated black so it looks like new. My wife, unfortunately is experiencing arthritis in her hands and may have trouble operating the clutch so I may have to install a hydraulic clutch, but what the hell is a couple hundred more at this point. Unfortunately life kept getting in the way but I am bound and determined to have it back on the road this year...
 
I have used Partzilla in the past but couldn't remember the name. It's hell getting old. Part of the problem is I started this restoration/modification of my Yamaha XS650d/Velorex Sidecar outfit in 2007 after my wife asked me when I was going to get "her" sidecar outfit running (we also have a 05 Harley ultraclassic sidecar outfit). When she asked when I was going to get it running what I'm sure I heard was "get it running, I don't care what it costs" so needless to say I have spent much more than it will ever be worth but we took our honeymoon up to West Edmenton, Alberta from our home in Washington State so it has "sentimental value." It was her first experience with motorcycling and she has loved riding ever since. I had 15" automotive spoked rims laced to all three hubs so I can run car tires, Had a leading link front end custom built to reduce the trail, and installed dual discs on the front. I installed a big fin 750cc cylinder block, had the crank turned to an 83 degree offset and of course the cam cut and welded for the new timing. I have installed a high output alternator and a Pamco electronic ignition along with Mikes XS Green Monster coils. I have a nephew who owns a chrome shop in the Sacramento area and so I got over $2,000.00 worth of chrome plating for free :p. I had the frame of both the bike and the sidecar powder coated black so it looks like new. My wife, unfortunately is experiencing arthritis in her hands and may have trouble operating the clutch so I may have to install a hydraulic clutch, but what the hell is a couple hundred more at this point. Unfortunately life kept getting in the way but I am bound and determined to have it back on the road this year...
Thanks. I have not received my replacement part yet but others had asked me to post the resistance when i got it. i had figured it was going to be a low value so you just confirmed that.
 
@Nelson , it seems the answer to your question is 3.8ohms. I removed the resistor from my 77 XS650D a few minutes ago. That's another few grammes of 47 year old electrical detritus I'm not using. Picture -

View attachment 326239
Here's a diagram for the resistor circuit that I marked up a while ago. I just added your 3.8Ω value to it. Feel free to keep and share it.


77_XS650D Light resistor.PNG
 
@Nelson , it seems the answer to your question is 3.8ohms. I removed the resistor from my 77 XS650D a few minutes ago. That's another few grammes of 47 year old electrical detritus I'm not using. Picture -
Cool, thanks.
Now my CDO wants to know: what resistance reading do you get when you put the test leads together?
 
Ah, that's going to be tomorrow I'm afraid.
Not sure if I'm gonna survive the night. There's gonna be some nail biting for sure! :D

Some good DMMs have a zero feature for resistance measurements to take the leads out of the equation. Remember the "old" analog multi-meters with adjustable zero? :)
 
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