tarapajero1
Member
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- Mazda CX-5
Some websites recommend a pair of load resistors for LED turn signal lights. Will it work or burn out faster if I don't get load resistors?
Led turn signals question
- Thread starter tarapajero1
- Start date
davidhbrown
Member
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- 2013 CX-5 GT AWD/Tech
Electronically, all LEDs require a load resistor because LEDs are a current-driven semiconductor rather than a voltage-driven resistive load like a regular incandescent (halogen/whatever) lamp. Presumably, any competently designed aftermarket LED would include that basic protection for the LED itself, ensuring that the LED will last its rated life.
However, that small resistance is not necessarily going to be the same amount of resistance that the car's computer was expecting to see from the regular incandescent lamp's filament. A traditional lamp works because the filament is a relatively poor conductor (a resistor); as electricity passes through it, it heats up to the point where it glows. When the driving circuit does not see this resistance (because you've replaced the filament with an LED), it might ignore it, but is as likely to suffer a variety of issues, ranging from weird blinking rates on turn signals, to the check brake light coming on, to error codes.
So I think the load resistor you're reading about is something that replaces the resistance of the filament -- over a larger area so it doesn't get white-hot! -- for the sake of assuring the computer all is well (or in a much older car, letting the bimetal blinker heat up at the proper rate).
(Haven't mucked with the car myself, but I've built plenty of circuits that use LEDs and regular lamps in other contexts.)
However, that small resistance is not necessarily going to be the same amount of resistance that the car's computer was expecting to see from the regular incandescent lamp's filament. A traditional lamp works because the filament is a relatively poor conductor (a resistor); as electricity passes through it, it heats up to the point where it glows. When the driving circuit does not see this resistance (because you've replaced the filament with an LED), it might ignore it, but is as likely to suffer a variety of issues, ranging from weird blinking rates on turn signals, to the check brake light coming on, to error codes.
So I think the load resistor you're reading about is something that replaces the resistance of the filament -- over a larger area so it doesn't get white-hot! -- for the sake of assuring the computer all is well (or in a much older car, letting the bimetal blinker heat up at the proper rate).
(Haven't mucked with the car myself, but I've built plenty of circuits that use LEDs and regular lamps in other contexts.)
carlosnest
Member
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- Mazda CX-5
So, got any answer for this? I'm planning to change my turn signal light to LED. Hope people who do this can please give some commend here. Thanks! 
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- 2014 & 2019 CX-5 Touring(s)
Hmm, a little bit of misinformation is around for this
The "load" resistors mentioned for LEDs are, in fact, low ohm power resistors (generally 6ohm, 50watt) that are placed IN PARALLEL with turn signal replacement LEDs to draw the same current as the regular incandescent bulb would that you are replacing. This is because most/all cars have circuitry that monitors the load to detect when a bulb has burnt out. That's why the signals 'hyper-flash' (fast flash) to indicate you have a problem. This was actually a side-effect in older cars that used the bimetal flasher units, but has been implemented/emulated in circuitry in modern cars for the same warning effect.
LEDs use much less current than incandescents and the car 'thinks' the bulb has burnt out and so hyper-flashes. The load resistor increases the load on the circuit and fools the car into thinking all is well.
This generally applies only to the turn signals, as I said. But some cars DO have the sensor circuitry on other circuits too and will result in a "bulb out" warning in the dash (though not, I think, the CX-5).
So, in answer to the OP's question, your LEDs will work without these, but your turn signals will probably fast flash.
The "load" resistors mentioned for LEDs are, in fact, low ohm power resistors (generally 6ohm, 50watt) that are placed IN PARALLEL with turn signal replacement LEDs to draw the same current as the regular incandescent bulb would that you are replacing. This is because most/all cars have circuitry that monitors the load to detect when a bulb has burnt out. That's why the signals 'hyper-flash' (fast flash) to indicate you have a problem. This was actually a side-effect in older cars that used the bimetal flasher units, but has been implemented/emulated in circuitry in modern cars for the same warning effect.
LEDs use much less current than incandescents and the car 'thinks' the bulb has burnt out and so hyper-flashes. The load resistor increases the load on the circuit and fools the car into thinking all is well.
This generally applies only to the turn signals, as I said. But some cars DO have the sensor circuitry on other circuits too and will result in a "bulb out" warning in the dash (though not, I think, the CX-5).
So, in answer to the OP's question, your LEDs will work without these, but your turn signals will probably fast flash.
carlosnest
Member
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- Mazda CX-5
Thanks. So if we putting on the load resistor, will it settle the fast flash problem?
Chris_Top_Her
Contributor
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- San Antonio, Texas
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- '15 CX-5 Miata AWD
Using the 6ohm/50w resistors Red Baron mentioned will net you good results. have replaces all of my lights with LEDS, except the brake light and headlights (tech pkg). http://www.ebay.com/itm/Load-Resist...Parts_Accessories&hash=item3f2529395c&vxp=mtr generic ones like this work well, I have been using mine for months and no burnt out led's, my front and rear led's flash in unison and they don't get super hot (don't mount to plastic though).
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- 2014 & 2019 CX-5 Touring(s)
OK, I've held off saying this 'cos many people don't like hearing their "baby is ugly". The majority of aftermarket LEDs are not worth it and even downright dangerous. The reason is that they are NOT AS BRIGHT as the bulbs they replace, certainly the turn signal and brake bulb LEDs (the running lights may be OK, but then, what's the point?). I know a bunch of people will reply that theirs look "just as bright as stock", but unless you are running at least 10 real watts per bulb (NOT 'marketing' watts) they're not putting out as much light as OEM incandescents. Fact of life. Then if you try to run 10W bulbs, they don't have enough heatsink, or cooling space, and either melt plastic or have shortened life (or both).
I converted my other car to LEDs and had to fab custom LED installations and tear the reflector assemblies apart to do so. I ensured equal or greater light throw across an equivalent wide angle with a lumen (light) meter. Not an easy task.
I converted my other car to LEDs and had to fab custom LED installations and tear the reflector assemblies apart to do so. I ensured equal or greater light throw across an equivalent wide angle with a lumen (light) meter. Not an easy task.
SayNoToPistons
Wheels, not rims...
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- CX-5 GT AWD w/ Tech, RX-8 GT 6spd w/ 'goodies'
Your statement may be true for the lower end of the LED cost spectrum and the "brightest" automotive LED replacements 2-3 years ago. Fortunately LED's have come a long way... The higher end LED's with advanced SMD's like Tritons and CREE's can be significantly brighter than incandescent bulbs they replace.
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- 2014 & 2019 CX-5 Touring(s)
That's theoretically (possibly) true. But there are some realities of physics here. Even top bin LEDs have to be driven hard and so put out a lot of heat. Accordingly they NEED big heatsinks. There's not enough space in a reflector designed for standard bulbs to fit high-current LEDs, and the requisite heatsink, through the hole. Thus, the LEDs are underdriven and underperform. Plus the light that they DO give is badly scattered by a reflector system not designed for multiple point sources, so the results are not good. Don't believe the marketing mis-info.
Just as an example, the photo below, is of a 10W (6 CREE LED) PAR30 downlight bulb. Just 10W, yet look at the size of the heatsink needed. No way you fit this into a CX-5 reflector - certainly without cutting it apart. Car manufacturers design LED light systems with many smaller-wattage LEDs with individual lenses or reflectors properly designed to direct the light. You can't get there from here
SayNoToPistons
Wheels, not rims...
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- CX-5 GT AWD w/ Tech, RX-8 GT 6spd w/ 'goodies'
Notice I said "incandescent bulbs they replace". Let me be more precise and specific, the incandescent without tungsten filament with bromine/iodine. Those include various small bulbs like the brakes, signals, festoon, P13W, and 194 wedge. I am not talking about direct replacements for bulbs such as the higher output halogens like the H11 in the fogs and xenons.
You just compared a household downright bulb to an automotive application. It is not on the same spectrum of design. We both know there is a clear difference in internal build based on power application and dimension.
I know I didn't spend the effort and money to obtain an engineering degree without knowing my physics. (rofl)
You just compared a household downright bulb to an automotive application. It is not on the same spectrum of design. We both know there is a clear difference in internal build based on power application and dimension.
I know I didn't spend the effort and money to obtain an engineering degree without knowing my physics. (rofl)
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