New LED Head Light - casuing issues

I have a 1982 XJ750J Maxim (the one with the LCD dashboard / LCD fuel gauge).
I changed out the standard Halogen head lamp bulb with an LED bulb. I like the new light, nice and bright - however, there must not be enough draw for the Headlight Warning light on the dashboard to turn off - the system thinks my headlight is burned out. I read through a lot of the electrical, switch, relay, diode information on this website. I see other models have a headlamp relay (with a yellow tab) and the instructions to bypass (jumper wires) that relay are in the readings... however, my model does not have that relay - I am wondering if there is still a way to bypass the head light warning light on the dash.
Once this is solved, I will move onto the next electrical issue - provided this issue is not the cause of both.

 

Remove the light bulb (in the dash) under that particular display.............

 

It is not a light bulb for the warning indicator - it's a section of the LCD screen

 

Install a load resistor inline of the power leads of the headlight.

 

This. Unless someone else knows a method for bypassing the circuit.

 

thanks everyone... I am willing to try a load resistor if you have more details, like what size.

 

this might be you, from the xjcd

What happens in the computer? The current goes onto the main circuit
board where each wire (high and low beam) goes to a coil which is
wrapped around a reed switch. When current is running through one of
the coils, a magnetic field is induced which triggers the reed
switch. The reed switch is connected to the computer, and allows the
computer to know when a headlight is burnt out. If a headlight is
out, no current will be in the coils and the reed switch won't
trigger--the computer sets a warning "HEAD" and a flashing light.

now how to fix it, get a magnet, find those reed switches and close them with your magnet.

 

I am not aware of any way to bypass the headlight warning circuit. It's all about current, and when you switch to a lower wattage device that draws less current the CMS will sense this and set a fail. It doesn't matter if you have a headlight relay or a set of contacts in the right control to apply power to the headlight.

I would have also thought that the headlight circuit worked similar to the tail and brake sensing circuits, which utilizes low value current sense resistors (not reed switches as described in the XJ CD) to convert the current to an expected voltage. SQLGuy did a fairly detailed explanation of this for the tail and brake light in this post:

http://www.xjbikes.com/forums/threads/how-to-convert-to-leds-and-still-have-everything-work.14068/

If the headlight circuit does incorporate the same design, then the same modification could be made using the diodes in place of the headlight sensing resistors in the CMS. Since the headlight is very similar in wattage (55/60) to the brake light (54), it is highly likely the modification could be done but I would consider it quite ambitious.

The size of the load resistor will depend on the wattage of the new headlight. You will want to size the resistor to return the system to the power of the original headlight - so new headlight wattage plus load resistor equals original wattage. Unfortunately, this somewhat ugly modification X2 for low and high beam will also increase the line drop and reduce the voltage to your new headlight causing it to dim slightly.

Edit: Power requirements for load resistors and headlight reed relay - see next post

 

Polock for the win...........

 

Not sure if the OP is still looking, but what bulb did you use?

OK, so this sparked my curiosity a bit and since I had an older Atari assembly I decided to take a look. It's a fairly tedious process to disassemble the Atari to this level.

I also tested the reed relays to see what the current requirement would be to detect a headlight fail condition. The reed relays appear to be the same device for high and low beam, but at this level it is impossible to see any markings to be sure. They contain a set of normally open contacts.

The low beam reed relay closed the contacts at 1.1 amps, the high beam reed relay closed the contacts at .9 amps. The fact that the high beam current was lower than the low beam current suggests they are the same part and part tolerance is a factor. This is well below the headlight current for the 55/60 watt setup, so it appears Yamaha wasn't concerned with a dim headlight excepting they did use the reed relay vs. a resistor to limit line loss.

So, if load resistors were to be used, keeping in mind this much lower current requirement to set a safe condition, then the load resistor could be reduced significantly compared to the load of the light.

I don't have much knowledge on LED bulbs, but the quick look I did at superbrightleds.com the recommended LED bulb would consume enough power that a load resistor would not be needed. However, in their specification they don't identify the terminals, and the recommendation was for a single brightness. Since the CMS checks the filaments looking for a high and low, perhaps selecting a different LED bulb would eliminate the need for load resistors.

 

Thanks Rooseter53 -
Here are the details of the bulb I am using:

30W 2000LM H4 BA20D H6M
LED COB Motorcycle/Bike Hi/Lo
Xenon White Headlight Lamp (Color: White)
Material: Aviation aluminum
Built-in radiator
Voltage: DC 12-85V
2000LM,and 360 lighting, more bright,30% improved.
Color Temperature: 6000K, White light

However - that data is from the website [https://www.wish.com/c/5629b1a2f16f26204bbda8c3]
I will try to put an amp meter on the bulb in the next few days.

Just a thought. Do you think it's possible (after digging deep into the assy) to by-pass the reed relays with a jumper?

What's funny is; the draw must be just barley under the limit because the LCD "HEAD" indicator stays on, but there is no red warning light that I need to clear.
So it is really just a minor inconvenience at this point - but I still would like to resolve.
thanks for all your help so far - I'll post what I discover about the amp draw on the bulb

 

Great pics! Very interesting.

 

do you have a photo or link to the bulb

 

I wonder if it is something to do with the basic function of a diode. Since it is just a light emitting version after all.
hmmm hmmm...

 

That is possible, but hopefully it can me made to retain the functional warning as headlights are important, even in the daytime. If a much smaller load resistor can be used than I originally speculated on, then that may be a good way to keep the functionality of the CMS and not ugly things up with massive heat producing load resistors.

This link did not work. Can you provide a link so we can look at the exact bulb that you have?

I will have to try and test the internal logic of the headlight out and warning light (unless someone already knows this). Per the FSM, any failure resulting in a fault should activate the flashing warning light. However, it could require that neither filament be working to set the flashing light, whereas only one filament out that is checked at power up would just give the LCD warning. This will take a bit of creativity so possibly a couple of days or more.

Edit: no special check at power up. The bulb current and filament are monitored continuously and will set the head warning and flashing warning light if either condition occurs.

That would be some good information and along with the LED specifications could add some insight to what might be occurring.

 

Try this - at wish.com - type in the search for "30W 2000LM H4 BA20D H6M LED COB Motorcycle/Bike Hi/Lo Xenon White Headlight Lamp " - that is the exact bulb I have. Again, I'll through a meter on the bulb tonight and come back with some data on amps.

 

I think I had found it earlier on Ebay - this looks like the same one. With wish.com you have to create an account.

http://www.ebay.com/itm/30W-H4-BA20...ash=item43e760072a:g:fMYAAOSw~bFWJf-m&vxp=mtr

The wiring instructions seem to contradict how to wire it up when comparing the annotated lines to the label on the white wire. So do you have a functioning high and low beam?




Edit: Not the OP's bulb

 

Could be, particularly if there is an initial power up test the LED may be too slow compared to the incandescent in the initial current draw. I need to verify or have someone confirm this sequence and logic.

Edit: The LED bulbs contain a constant current source. The voltage used for filament check in the CMS is sourced from and internal 5V regulator. Consequently, the filament check has no hopes in working with the LED bulb.

 

Not broken link:

https://www.wish.com/m/c/5629b1a2f16f26204bbda8c3

It's reading the trailing ] as part of the link in the post above.

 

Guys - I really appreciate the help so far. Here is what I discovered this evening:

Yes, the high and low beams both work on the new LED as designed. (except for the LCD warning indicator)
Here is a photo of the light

Now some more details.
The bulb is marked High Beam 18W, Low beam 12W
At 12 volts that means I am drawing
low beam = 1amp
high beam = 1.5amp

I placed a load resistor in-parallel with the low beam wire.
It's a 50W 25 ohm load resistor.
However, this did not rectify the LCD warning indicator "HEAD" on the dash.
I can try another load resistor tomorrow - next up is a 50W 3 ohm resistor.
I might be chasing the wrong things here, but at least I am discovering what won't fix it