Inline Resistor - HOT

[thedoughboy]

I have DEPO rear led tail lights. I installed an inline resistor. I recently removed one of my tail lights and discovered the resistor had melted through the rear of the light housing.

Do all resistors get this hot? If I apply the brakes the resistor heats up fast. Too hot to touch.

If they do get this hot where do you guys mount them?

 

[thedoughboy]

Bump...to the top

 

[Kernal]

Got photos of the resistor and the carnage?

 

[thedoughboy]

@landcrshr Any insight?

 

[PeterTheBeater]

Why did you install a resistor? To stop the dash light from flashing too fast?

 

[Saito]

Why did you install a resistor? To stop the dash light from flashing too fast?

Guessing this would just be for the blinker circuit.

 

[thedoughboy]

The "hyperflash" encountered when using LED turn signal is handled by a new flasher relay located in the driver's side kick panel. The inline resistor I have is on the brake circuit. The resistor I installed helped with the intensity of the rear driving lights vs brakes lights (at night). It has been a long time but I believe the rear tail lights appeared as if the brakes were on, until the resistor was installed. The resistor toned down the intensity of the rear lights at night with the headlights on.

 

[landcrshr]

@landcrshr Any insight?

Sorry, I have no personal experience with this. But yeah, some resistors can get really hot during normal operation. Just look at the size of heat-sink that houses your fuel pump resistor.

 

[PeterTheBeater]

The "hyperflash" encountered when using LED turn signal is handled by a new flasher relay located in the driver's side kick panel. The inline resistor I have is on the brake circuit. The resistor I installed helped with the intensity of the rear driving lights vs brakes lights (at night). It has been a long time but I believe the rear tail lights appeared as if the brakes were on, until the resistor was installed. The resistor toned down the intensity of the rear lights at night with the headlights on.

What resistor did you use? You might have the correct amperage but the resistor might not be able to handle the wattage you're putting thru it.

 

[thedoughboy]

What resistor did you use? You might have the correct amperage but the resistor might not be able to handle the wattage you're putting thru it.

I would need to remove my tail light to find out. Do you have a recommendation on what I should use? I bought some resistors of eBay (I believe) recommended by thread on DEPO Led lights. I am trying to track that thread down but am not having much luck.

 

[ppc]

Do you have a recommendation on what I should use?

Get rid of the LED bulbs. There use is nothing less than a self inflicted problem. Use a standard, regular incandescent bulb and you problem is gone.

 

[PeterTheBeater]

I would need to remove my tail light to find out. Do you have a recommendation on what I should use? I bought some resistors of eBay (I believe) recommended by thread on DEPO Led lights. I am trying to track that thread down but am not having much luck.

I'm not 100% sure on the tail lights or the wattage, but I'm going to assume that the LED bulbs are not interchangeable.
You can run two resistors in parallel, which would double the wattage they can handle. Should dissipate heat a bit.

 

[thedoughboy]

Get rid of the LED bulbs. There use is nothing less than a self inflicted problem. Use a standard, regular incandescent bulb and you problem is gone.

The rear DEPO tail and brake lights are built in LED panels. They are much brighter and clearer than OEM. In addition, you can run pretty high wattage reverse lights. I know I could run the old stuff but I like figuring this stuff out.

 

[robnicko]

FWIW, i tried LED globes in the original housings and had to use the inline resistors so the blue dash high beam indicator and also driving lights would work.
After about an hours drive at night the resistor was so hot i decided against using the LED's and resistor combo.
Now ive settled on good quality globes and also gave the inside of the headlights a good clean with soapy water and theyre great.

They say to mount the resistor to a metal surface so it acts like a big heat sink but i just never felt confident that these things wont catch fire one day......

 

[smritte]

There's three ways to do this, the proper way, the harder way or the half azzed way. The way its hooked up now is not the proper way. Its the half azzed way. Unfortunately this is the way quite a few manufactures chose in the past. I had never seen it used the way yours is, it was done to change the speed of turn signal flashers.

The proper way is to swap out the tail light assembly with LED's of the correct output. Obviously the one's you have are not. Based on your posts, this is not going to happen.

The way your doing it now, your using a resistor to consume power, limiting it from the lights. The resistor will change the power to heat. If the resistor wasnt big enough, it most likely would have already burned out. You can remove the resistor, test it and get two that are double the resistance rating, hook them in parallel and split the power between them. The problem is though, the same heat will be generated, just split between them. This will not remove the heat issue.

If your going to keep the tail lights, how you should be doing it is an inline regulator, not a resistor. A pulse width type would be best. Now you can hook it up, adjust to whatever you want and just hide it in the rear quarter. The module will most likely be 3X1x1. These run somewhere around $20.
Here's one I just searched out. This ones a bit overkill and I would look for one that doesn't have the switch hanging off it. Its a start.

 

[PeterTheBeater]

There's three ways to do this, the proper way, the harder way or the half azzed way. The way its hooked up now is not the proper way. Its the half azzed way. Unfortunately this is the way quite a few manufactures chose in the past. I had never seen it used the way yours is, it was done to change the speed of turn signal flashers.

The proper way is to swap out the tail light assembly with LED's of the correct output. Obviously the one's you have are not. Based on your posts, this is not going to happen.

The way your doing it now, your using a resistor to consume power, limiting it from the lights. The resistor will change the power to heat. If the resistor wasnt big enough, it most likely would have already burned out. You can remove the resistor, test it and get two that are double the resistance rating, hook them in parallel and split the power between them. The problem is though, the same heat will be generated, just split between them. This will not remove the heat issue.

If your going to keep the tail lights, how you should be doing it is an inline regulator, not a resistor. A pulse width type would be best. Now you can hook it up, adjust to whatever you want and just hide it in the rear quarter. The module will most likely be 3X1x1. These run somewhere around $20.
Here's one I just searched out. This ones a bit overkill and I would look for one that doesn't have the switch hanging off it. It’s a start.

Two things at 70*F does not equal one thing at 140*F

 

[smritte]

Two things at 70*F does not equal one thing at 140*F

Im sorry, your post doesn't make sense to me. can you explain?

 

[PeterTheBeater]

You can remove the resistor, test it and get two that are double the resistance rating, hook them in parallel and split the power between them. The problem is though, the same heat will be generated, just split between them. This will not remove the heat issue.

I agree with you that the best way to swap the LED themselves.
However, splitting the power for two resistors in parallel will not produce same level of heat. Two resistors will be half as hot as if there were just one resistor.
I think what you're saying is that while the resistor is not as hot, there are two of them, so the heat would be the same. While I guess the energy produced from them is the same, they will still only be half as hot temperature wise.

 

[smritte]

However, splitting the power for two resistors in parallel will not produce same level of heat. Two resistors will be half as hot as if there were just one resistor.

That is correct. I never said twice the heat. You may have confused my "Twice the resistance" statement. Two resistors in parallel will equal half the total resistance. To end up with the same resistance as there is now, you would double the resisters in parallel.

BTU (heat) directly relates to wattage. You calculate the total wattage consumed in a circuit and convert that to BTU. 1watt = 3.412142 BTU/hr
By splitting the the resistance, your splitting the BTU consumed by the resistors. Setting them on a heat sink works but one should calculate the heat dissipation of the material and use the btu's to determine the size of the sink.

Again, this is not how I would have done it. When this method appeared years ago, most of us were appalled. It works but its not really the way to "dim" led's.

 

[thedoughboy]

There's three ways to do this, the proper way, the harder way or the half azzed way. The way its hooked up now is not the proper way. Its the half azzed way. Unfortunately this is the way quite a few manufactures chose in the past. I had never seen it used the way yours is, it was done to change the speed of turn signal flashers.

The proper way is to swap out the tail light assembly with LED's of the correct output. Obviously the one's you have are not. Based on your posts, this is not going to happen.

The way your doing it now, your using a resistor to consume power, limiting it from the lights. The resistor will change the power to heat. If the resistor wasnt big enough, it most likely would have already burned out. You can remove the resistor, test it and get two that are double the resistance rating, hook them in parallel and split the power between them. The problem is though, the same heat will be generated, just split between them. This will not remove the heat issue.

If your going to keep the tail lights, how you should be doing it is an inline regulator, not a resistor. A pulse width type would be best. Now you can hook it up, adjust to whatever you want and just hide it in the rear quarter. The module will most likely be 3X1x1. These run somewhere around $20.
Here's one I just searched out. This ones a bit overkill and I would look for one that doesn't have the switch hanging off it. Its a start.

Thanks for your input. Interesting, some individuals have reported that they did not need a resistor when using these lights. From what you said this would indicate their DEPO tail lights had the correct output LED installed. I am going to remove my resistor to refresh my memory as to EXACTLY why I had to install it. I will report back later tonight or tomorrow.