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flasher for LED turn signals
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autostaretx
Erratic Member
The resistors go in parallel with the LEDs... the goal is to suck enough power from the Sprinter to keep it happy.
So "in parallel" means that the + side of the resistor gets connected to the + wire feeding the bulb/LED.
The - side of the resistor gets tied to the frame ground somewhere. It doesn't need to squeeze into restricted space in the tail light unit (if you wish).
--dick
p.s. resistors don't care which end is + or - ...
Shortiez
Two High Roof 118s
To summarize the last 5 pages I believe what was agreed upon and tried successfully was:
10 Ohm resistors with max power handling of 25W in parallel with the new LED lights.
It worked.
The temp ran a little hot for my taste though, so personally I'm going to get some 100W unit which run about a buck-fifty on eBay these days.
I'll add a little experience of my own so maybe someone can save repeating it. I did a little math that led me to conclude a 4 Ohm resistor would be about right to emulate the parallel resistance of both the front, side and backlights, ordered, and installed these. It does work to slow the rate. However, they got to 210F on a 50F evening in about 10 min. I'm not okay with that since I'd like it to work with emergency flashers on for 3 hours at noon in a Death Valley summer with some margin.
So began to suspect that 4 Ohms was too little. So I wired my two resistors in series to make 8 Ohms and the flashing rate didn't change at all! Hmmm. I thought it would, but I guess it's not some linear function but a smarter system. IE there's a threshold over which it's happy.
10 Ohm resistors with max power handling of 25W in parallel with the new LED lights.
It worked.
The temp ran a little hot for my taste though, so personally I'm going to get some 100W unit which run about a buck-fifty on eBay these days.
I'll add a little experience of my own so maybe someone can save repeating it. I did a little math that led me to conclude a 4 Ohm resistor would be about right to emulate the parallel resistance of both the front, side and backlights, ordered, and installed these. It does work to slow the rate. However, they got to 210F on a 50F evening in about 10 min. I'm not okay with that since I'd like it to work with emergency flashers on for 3 hours at noon in a Death Valley summer with some margin.
So began to suspect that 4 Ohms was too little. So I wired my two resistors in series to make 8 Ohms and the flashing rate didn't change at all! Hmmm. I thought it would, but I guess it's not some linear function but a smarter system. IE there's a threshold over which it's happy.
ECU
2006 T1n 118 Sprinter
I had the setup using 100w resistors. Big ones. They got hot, I wired it at a point that the one resistor worked for front and back together. They lasted for about three years before the resistors failed.
The bulbs also were losing some of the LED components and became darker and darker.
This was my second setup for LEDs.
I switched back to regular bulbs after I replaced the multi function switch. could the LEDs have led to the switch failure. I thought so, thus I swapped to regular bulbs. Now I can leave my flashers on with out concern.
The bulbs also were losing some of the LED components and became darker and darker.
This was my second setup for LEDs.
I switched back to regular bulbs after I replaced the multi function switch. could the LEDs have led to the switch failure. I thought so, thus I swapped to regular bulbs. Now I can leave my flashers on with out concern.
ECU
2006 T1n 118 Sprinter
I did not notice a brighter light when comparing. The standard bulbs have a slower ramp up and down vs the instant response of the LED. Total duration and brightness the same.
LED headlights were lame. Dim, diffused, lacked distance.
When I added the fog lights to my headlights (replaced housings), I basically made the fog the DRL lights. I thought about adding relays to mimic the new car lights. Then I had to say the additional time vs the age of my vehicle and decided against more things to do.
LED headlights were lame. Dim, diffused, lacked distance.
When I added the fog lights to my headlights (replaced housings), I basically made the fog the DRL lights. I thought about adding relays to mimic the new car lights. Then I had to say the additional time vs the age of my vehicle and decided against more things to do.
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sikwan
06 Tin Can
I haven't looked, but isn't there aftermarket LED bulbs that come with logic built into the base of the LED so that you don't have to use resistors? The logic would convert the 12V input to a PWM output, so that the LED would turn on properly without affecting the supply.
LED's are known for low power consumption. Putting a resistor in parallel defeats that purpose.
Not trying to bust any chops, just wondering.
LED's are known for low power consumption. Putting a resistor in parallel defeats that purpose.
Not trying to bust any chops, just wondering.
I just want super bright turn signals and brake lights.
Shortiez
Two High Roof 118s
Thanks for the experience ECU. Well, my bulb burned the contact, so I figured an LED wouldn't draw enough current/get hot enough to do that. So that's part of the reason I'm trying to do this.
What resistance value were your resistors? Where did you place them?
Did you screw them to the frame so they could shed more heat?
Maybe I should be testing 12, 14, 16 Ohm, maybe those work too.
Hoping there's something I can do to make this work, permanently.
autostaretx
Erratic Member
Correct ... you're trying to fool the Sprinter into thinking a 21 watt bulb is still out there.
So it's going to be creating heat that's the product of the voltage squared divided by the resistance.
The voltage is going to be (engine running) 14 volts.
A resistor rated for 25 watts simply means the resistor itself ("in free air", depending upon design) won't melt at that load. A 100 watt resistor will simply be physically bigger (greater surface area to radiate heat) ... but will still be dumping 21 watts (or whatever the V*V/R says).
Given your 4 ohm example, 14*14/4= 49 watts ... twenty percent more than two 21 watt bulbs.
Unlike 1950's automobiles, the Sprinter's flash rate is not affected by small/medium resistance changes ... it will be X flashes per minute.
Only when the Sprinter's "logic" detects a too-high (or too-low) current draw will it shift to "fast flash". It's an all-or-normal flip ... there's no "half way" if you use a "half load" "bulb".
Increasing your resistance to 8 ohms brought the heat dissipation down to 25 watts .... distributed across the two resistors, so they're only seeing 12.5 watts each.
--dick
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ECU
2006 T1n 118 Sprinter
I had the big square ones that came with the lights. I don't remember the ohms. I mounted them via wires, hanging in air. Behind the fuse block 1. This way one location would fit both front and back. I think I clipped in to the back of the flasher.
There is a possibility that new bulbs will last longer. My purchase of about 8 years ago, were likely of less quality.
There is a possibility that new bulbs will last longer. My purchase of about 8 years ago, were likely of less quality.
WilliamJames
New member
Ohms Law. Resistance in Ohms = Voltage/Current. For a 21Watt lamp (normal wattage in the United Kingdom) at 12V that reqires 1.75A (21W/12V). A 6W led lamp takes 0.5A at 12V (6W/12V). Therefore 1.75A - 0.5A leaves 1.25A to go through the resistor. To make it easier lets say 1.2A.ok, just ordered 2 of the ones at the link you posted -- honestly don't know how you came about determining the resistance or wattage but I'm going to take your word for it since you guys sound like you know what you're talking about. Appreciate it!
Using Ohms Law =12V/1.2A = 10 Ohms. It is what all electricians learn on their first day at college. ?
A 10 Ohm resistor has to go across the positive and negative wires to each of your flashing LED indicator lamps to make them flash slowly enough to conform with the law in most countries. This appears to be the only option with a Mercedes Sprinter Van because the flashing unit is incorporated in a larger unit. It may be possible to be altered but for that we need an auto electrician! Please note: the 10 0hm will need to be a power resistor capable of dissipating around 15 Watts and it is best to fasten it in some way to the metalwork of the vehicle to act as a heatsink.
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Deleted member 50714
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Tried it once...way too much work.