I don’t really have enough details here to be able to help you out. That 48V would need to be stepped down to about 5-6v to be usable by these LEDs. Do you have a headlight already that steps down the voltage and you just need new LEDs to put in it?
Thanks for getting back to me Stephen, in the attached photos you might see how this pc board fits into a headlamp assembly. I have measured the voltage to the resistor at 53v and nothing after the first led. Individual continuity tests on each of the seven
Led’s reveal open circuits. The resistor measures 1992 ohms and that’s about right according to the color code. Can you supply a voltage reducer to run your 5v Led’s and still provide good lighting. If so, how much?
If it is supplied from the voltage source That resistor will limit your current to 14mA as the LEDs are all in series.
Vsupply = Vleds + Vr.
Vled = 7*3
Vr = Vsupply - Vleds
CurrentLED = CurrentR = Vr/R = 27/2k = 0.0135mA
Changing the value of that 2K resistor would change the brightness of your LEDs though going too low will “let the smoke out”.Sorry if I went too maths. but Robin is right the 40V is fine as long as the current is limited.
You seem to have measured the LEDs on the resistance (Ω) function assuming you are using a digital multimeter. Unless all of them are actually open circuit.
This function will not output enough voltage on the leads to turn on a diode or other junction, certainly not a LED.
Use the “diode check” function. This will display open circuit in the reverse direction and display the actual forward voltage drop of the junction in the forward direction. In the case of a LED this could be anywhere between about 2V - 3V depending on colour. The LED may even light dimly. The diode check function will have a little picture of a diode symbol.
All of the diodes are in series so it would only take one to be open circuit to turn the lot off. You will have to check them individually as the diode check will not have enough voltage to turn all of them on. There would be no need to remove them for this. just remove power.
Looking at the photo I would check some of those soldered joints. A bad joint here would turn the whole thing off.