HOW TO: Turn Signal / Marker Light Combo WITHOUT Drilling into Marker Light Housing

[Ed_C]

Daniel Stern has dual-filament bulbs in the diagram but implementation is the same, just ignore the "parking lamp feed" wiring to the signal bulbs.

 

[APhelps]

Yes, that’s what I had in mind. Be sure to use the same resistors / diodes / bulbs I used.

[MENTION=146513]APhelps[/MENTION], you’re an EE, could you confirm this?
Jziggy wants to keep his turn signal functioning normally and his marker light to function like a dual filament bulb with a dimmer marker light and brighter turn signal light, basically do what I did but splice into the turn signal line rather than cutting it.

edit: see post 23.

 

[phattyduck]

No reason it shouldn't work but the turn signal bulb should appear dimmer since the current is going to divide by whatever the ohm value is of the marker. (see Kirchoff's Current Law for more info), I suppose one way around that would be to use a bulb that has is brighter with less wattage use (perhaps LED).

Also the marker bulb might blow out due to too much current through it if its not rated high enough (sort of doubt it though).

No, no... bulbs in the car are fed voltage, not current. The turn signal will stay the same brightness even if the corner light is fed the same signal.

Kirchoff's Law only applies to current sources (or when determining the split of current between two loads). In this case, the total current draw will go up by the draw of the corner light bulb - it won't reduce the draw of the turn signal bulb.

-Charlie

 

[APhelps]

No, no... bulbs in the car are fed voltage, not current. The turn signal will stay the same brightness even if the corner light is fed the same signal.

Kirchoff's Law only applies to current sources (or when determining the split of current between two loads). In this case, the total current draw will go up by the draw of the corner light bulb - it won't reduce the draw of the turn signal bulb.

-Charlie

Yep I stand corrected. Been a while since I've thought about basic circuits (do mostly programming related non sense these days). Should of drank more coffee this morning and refreshed my brain on circuits before commenting.

Just got to make sure the wire is rated to handle the load (I'd venture to guess it'll be though since Toyota over engineers things).

 

[APhelps]

Charlie,

I like this approach. Can you help me understand from a wiring perspective why it works that way?

Which LED bulb did you use?

Not sure if you've got your answer but by connecting the ground of the marker light to the positive of the turn signal light, when the turn signal light bulb grounds it is grounding the marker light as well. (i.e. they will flash together)

As far as them flashing opposite of each other, you would need to look at the rest of the circuit.

 

[Team_Jake]

If you want do do that, connect the ground wire (white-black) from your current corner light to the turn signal positive wire instead of ground. It will flash with the turn signals when the lights are off and opposite the turn signal when the lights are on, like this (ignore the switchback main turn signal, focus on the corner light):

YouTube

I also put in a very bright LED corner bulb to help out with brightness there.

-Charlie

Just one thing to note about this method, since it sets up a floating ground with the marker light, there can be some feedback issues. Before I setup my turn signals and marker lights with the diodes and resistors, I did this:

When my turn signal was on and marker lights off, some of the interior lights in the center dash console (around the radio and air controls) would flash along with the turn signal (it was faint but noticeable nonetheless).

But you don't mind that then I suggest going this route.

 

[JZiggy]

Just one thing to note about this method, since it sets up a floating ground with the marker light, there can be some feedback issues. Before I setup my turn signals and marker lights with the diodes and resistors, I did this:

When my turn signal was on and marker lights off, some of the interior lights in the center dash console (around the radio and air controls) would flash along with the turn signal (it was faint but noticeable nonetheless).

But you don't mind that then I suggest going this route.

That would be a good reason to add a diode in the path from the turn wire to the marker ground, right?

 

[Team_Jake]

That would be a good reason to add a diode in the path from the turn wire to the marker ground, right?

With the Floating Ground method, current travels through the light bulb one direction with only the marker light on, and travels the other direction with only the turn signal on (and with both on at the same time cancel each other out). Diodes only allow current to travel in one direction, so adding in a diode somewhere in the Floating Ground method does you no good. That's why I did it the way I did.

 

[Bad Luck]

Just one thing to note about this method, since it sets up a floating ground with the marker light, there can be some feedback issues. Before I setup my turn signals and marker lights with the diodes and resistors, I did this:

When my turn signal was on and marker lights off, some of the interior lights in the center dash console (around the radio and air controls) would flash along with the turn signal (it was faint but noticeable nonetheless).

But you don't mind that then I suggest going this route.

That's good to know. Thanks for sharing

 

[JZiggy]

Completed this mod and works as advertised. Thanks yall!

Before

Wired in and wrapped up

Wiring

 

[Ed_C]

Cool! Did you upgrade to amber 921 bulbs? Before I went LEDs I started with standard clear 921s then ambers.

 

[JZiggy]

Cool! Did you upgrade to amber 921 bulbs? Before I went LEDs I started with standard clear 921s then ambers.

Nope, I just left whatever bulb is usually in there. What do the 921s bring?

 

[Ed_C]

Nope, I just left whatever bulb is usually in there. What do the 921s bring?

They're the bulbs the OP upgraded his corner lights with, pretty decent increase in brightness over the smaller original corner light bulbs.

 

[JZiggy]

Like these?

 

[Ed_C]

Like these?

Yup! Clear 921s are usually found in reverse lights, had some spares when I changed my Tundra tail light assemblies so it was a free upgrade for the 4Runner.

 

[JZiggy]

Yup! Clear 921s are usually found in reverse lights, had some spares when I changed my Tundra tail light assemblies so it was a free upgrade for the 4Runner.

So I tried this and they work great! Way brighter and the amber color looks good. Thanks again.