Need some help from one of you electrical engineer types

[Dangerous Dave]

Don't know if a Scion xB is similar to yours.
Here's its headlight schematic.

https://scionlife.org/Scion_Docs/2006_xB_Wi...20headlight.pdf

Looks like the lamp power enters the common between the high and low beam filaments. The dimmer switch completes the circuit to ground for either the high or low beams. From this drawing I don't see how the lamps can affect the high beam indicator on the instrument cluster.

The xD wiring is very different. The H/B indicator on the xD gets its power through the headlight bulb, not from the dome fuse as in the xB. For whatever reason, the HID kit isn't passing the voltage on to the indicator, although I honestly don't understand why not. The previously mentioned idea works, I'm just not having any luck finding the correct resistor that will turn on the indicator without letting the smoke out of anything else. I haven't cooked anything yet, and I'd like to keep it that way, hence my quest for help from people who are better at this than I. I wish my file hosting site would do pdf's, then I could post mine up.

 

[mcatrophy]

...I wish my file hosting site would do pdf's, then I could post mine up.

If it helps, if you can send the pdf's by email, I could host them for you. PM me if so. (May be a delay in response because of time zones.)

 

[Dangerous Dave]

...I wish my file hosting site would do pdf's, then I could post mine up.

If it helps, if you can send the pdf's by email, I could host them for you. PM me if so. (May be a delay in response because of time zones.)

I can, but your e-mail address isn't in your profile. I'm tempted to try juggling resistor values to see what that yields me. Since the method you linked me to originally worked with a 1 ohm, 10 watt resistor (but the resistor got really hot), and the fellow who posted the fix claims to have used a 10k 1/4 watt with good results (although it didn't work for me), what do you suppose would happen if I used a 1/4 watt 5k or 2.5k resistor?? At $.99/5-pack, a little experimenting isn't going to break the bank. I sure would like to get this resolved though.

Thanks,

 

[mcatrophy]

Ok, after a PM and an e-mail session:

(Click on image for large view)



Having looked at the circuit, I can see what's happening. The high beam indicator (labelled "Beam") gets its positive supply through the filaments of the low beam bulbs.

Assuming the indicator wants about 20mA (typical for a LED), we need to feed it from a source resistance that won't impede this sort of current, let's say no more than 2 volts drop at 20 mA. So the resistor would need to be about 2/0.02 ohms or 50 ohms (47 in practice).

When in the low beam state, this will have the full battery voltage across it, so the power dissipation will be

14.5 x 14.5 / 47 = 4.5 watts.

This is still fairly high, and would need to be properly mounted to dissipate this sort of heat.

You could use a small conventional car bulb, a 5 watt tail lamp would be perfect; its cold resistance would be well below the 50 ohms giving full brightness to the "Beam" LED, and it is designed to work on the car's 12 volts, but it would need a suitable air volume round it to take the heat away.

 

[Dangerous Dave]

From a subsequent e-mail I got from mcatrophy;

The built-in resistor is likely to be something like 12/0.02 =600 ohms (12 not 14 because the LED drops about 2 volts whatever the current). To reduce the brightness noticeably, it would need the current halving, so a resistor around 600 - 560 or 680 are "preferred" values.
Power when not on full beam would be 14.5 x 14.5 / 560 = 0.375 watts. This is not very convenient, so maybe get some 330 ohm 1/4 watt, then put two in series.

BINGO!!! We have a winner! I stopped at Radio shack on the way home from work and picked up another $.99 pack of 330 ohm 1/4 watt resistors, put two in series and wired them across the vacant headlight connector for the high beam indicator power. Voila`! My high beam indicator now works with my HIDs, the resistors don't get hot, and I didn't let the smoke out of anything! Thank you VERY much mc for helping me resolve this small but annoying problem.