Hyperflash Resistor question
Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
Hyperflash Resistor question
I installed a LED brakelight kit from a forum vendor (that works very well) and I was concerned about the heat radiating off the hyperflash resistors. I did some research and found that the resistors used are very common parts in LED systems for lighting. Although these are commonly used resistors, I am concerned that the heat these things generate is quite high, especially since they are located behind the rear facia right behind the rear tail lights and thus don’t see much airflow due to being inside the bodywork. I have done some calculations that tell me that the resistors could be marginal in applications such as vehicles in Pheonix that have been out in the sun and driving in lowspeed situations with heavy brake usage such as in heavy traffic situations. I am concerned that these resistors can get up to about 200C (400F) in worst case conditions, and I am not sure how fiberglass, plastic, and wire harnesses will like that.
The current resistors supplied are 25W 8ohm. I am thinking of changing the resistor values to something higher to reduce current flow and thus reduce heat generation.
I was wondering if anyone has done and tests or runs with a different hyperflash resistor value???
Thanks!!!
The current resistors supplied are 25W 8ohm. I am thinking of changing the resistor values to something higher to reduce current flow and thus reduce heat generation.
I was wondering if anyone has done and tests or runs with a different hyperflash resistor value???
Thanks!!!
Team Owner
Joined: Mar 2008
Posts: 21,502
Likes: 465
From: Southern Utah
If the current ones are 8 ohm, that is the important spec. You may replace with a bigger 8 ohm resistor and the circuit will never know the difference. 25W is the power handling capacity. It is the amount of power (heat) that the resistor can handle. So you could do a 50 or 100W 8 ohm resistor, or if you can't find one, you could do two 25W 16ohm resistors in parallel, or two 25W 4ohm resistors in series. Important factor is that the overall resistance stays at 8 ohms. A trip to radio shack is in order...Hope this helps....
Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
My real question is whether 8ohms is indeed the minimum needed to avoid hyperflash. For example, can 10 ohms successfully avoid hyperflash? Can 20ohms successfully avoid hyperflash?
The reason I ask this is that (1) I don't like the idea of that kind of heat being generated under my rear facia regardless of how many resistors are wired in parallel , and (2) I don't want to suck out more current from a marginal electrical system (as documented by many DBS threads) than needed.
Anyone done any tests with something other than an 8 ohm resistor or currently is running resistors with other values that have had success in the field?
The reason I ask this is that (1) I don't like the idea of that kind of heat being generated under my rear facia regardless of how many resistors are wired in parallel , and (2) I don't want to suck out more current from a marginal electrical system (as documented by many DBS threads) than needed.
Anyone done any tests with something other than an 8 ohm resistor or currently is running resistors with other values that have had success in the field?
Race Director
Joined: Oct 2007
Posts: 11,367
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From: Edgewood Washington
St. Jude Donor '11-'12-'13-'14-'15
The resistor value should be about he same as the load it is replacing.
You should use resistors that have an integral aluminum heat sink, not just the cheaper solid ceramic variety.
If you use individual resistors on each rear turn signal, 4 total, instead of just 2, you will reduce the temp. of the resistors.
Use 50W resistors at a minimum and there are aluminum mounting brackets that are made for the resistors that increase the cooling capacity. V-LED's, online has these.
You should use resistors that have an integral aluminum heat sink, not just the cheaper solid ceramic variety.
If you use individual resistors on each rear turn signal, 4 total, instead of just 2, you will reduce the temp. of the resistors.
Use 50W resistors at a minimum and there are aluminum mounting brackets that are made for the resistors that increase the cooling capacity. V-LED's, online has these.
Pro
Joined: Apr 2008
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From: Paris
Actually you can knock it down a bit, it depends on what the rest of the load is.
From my experience, for the rear the BCM activates the hyper flash mode if the current drawn is lower than 3 amps.
Normally the turn signals should be pulling 4 amps total (2 per bulb).
I knocked down the current drawn (or increased the resistance) to be borderline on the hyper flash.
What I installed is a resistor of type TO-220 and stuck them on heat sinks.
Resistor on right bottom side of PCB.
a++ Cedric
From my experience, for the rear the BCM activates the hyper flash mode if the current drawn is lower than 3 amps.
Normally the turn signals should be pulling 4 amps total (2 per bulb).
I knocked down the current drawn (or increased the resistance) to be borderline on the hyper flash.
What I installed is a resistor of type TO-220 and stuck them on heat sinks.
Resistor on right bottom side of PCB.
a++ Cedric
Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
I installed both the LED brakelights and the sequential turn signal kit (sequential kit from Web Electric). The combination of the two really make the rear lighting spectacular!
Last edited by inthehunt2; Jul 28, 2009 at 10:13 PM.
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Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
Actually you can knock it down a bit, it depends on what the rest of the load is.
From my experience, for the rear the BCM activates the hyper flash mode if the current drawn is lower than 3 amps.
Normally the turn signals should be pulling 4 amps total (2 per bulb).
I knocked down the current drawn (or increased the resistance) to be borderline on the hyper flash.
What I installed is a resistor of type TO-220 and stuck them on heat sinks.
Resistor on right bottom side of PCB.
a++ Cedric
From my experience, for the rear the BCM activates the hyper flash mode if the current drawn is lower than 3 amps.
Normally the turn signals should be pulling 4 amps total (2 per bulb).
I knocked down the current drawn (or increased the resistance) to be borderline on the hyper flash.
What I installed is a resistor of type TO-220 and stuck them on heat sinks.
Resistor on right bottom side of PCB.
a++ Cedric
What R value did you end up with that worked? How high are your running the ohms?
Also, is the BCM smart enough to change the threshold for determining hyperflash based on system voltage (ie. does the current threshold for hyperflash change based on system voltage recognized by the BCM?)
Last edited by inthehunt2; Jul 28, 2009 at 10:20 PM.
Team Owner
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St. Jude Donor '05-'06-'07-'10
Steve,
I can't help with the Hyperflash resistors as I have not done nor looked in to this mod. I don't believe the heat to be a real problem. That temperature will be quite localized to the resistor and there is some air in there which will help to insulate from the temperature. As you noted, it is common to use resistors in parallel with LED's to aid in this type of application.
I can't help with the Hyperflash resistors as I have not done nor looked in to this mod. I don't believe the heat to be a real problem. That temperature will be quite localized to the resistor and there is some air in there which will help to insulate from the temperature. As you noted, it is common to use resistors in parallel with LED's to aid in this type of application.
Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
Steve,
I can't help with the Hyperflash resistors as I have not done nor looked in to this mod. I don't believe the heat to be a real problem. That temperature will be quite localized to the resistor and there is some air in there which will help to insulate from the temperature. As you noted, it is common to use resistors in parallel with LED's to aid in this type of application.
I can't help with the Hyperflash resistors as I have not done nor looked in to this mod. I don't believe the heat to be a real problem. That temperature will be quite localized to the resistor and there is some air in there which will help to insulate from the temperature. As you noted, it is common to use resistors in parallel with LED's to aid in this type of application.
Pro
Joined: Apr 2008
Posts: 728
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From: Paris
Cedric - This is EXACTLY what I am looking for!!!
What R value did you end up with that worked? How high are your running the ohms?
Also, is the BCM smart enough to change the threshold for determining hyperflash based on system voltage (ie. does the current threshold for hyperflash change based on system voltage recognized by the BCM?)
What R value did you end up with that worked? How high are your running the ohms?
Also, is the BCM smart enough to change the threshold for determining hyperflash based on system voltage (ie. does the current threshold for hyperflash change based on system voltage recognized by the BCM?)
My personal impression is that they have a current driven component that checks the draw in the BCM that is voltage independant.
My ohms aren't going to be yours because I have a circuit that is different then yours (mine is home made).
The first question that you need to answer how is the resistor connected?
If it's in serie you won't be able to do much because you may damage your downstream circuit (LEDS don't like voltage at all) if you change the value.
If it's in // you will need to determine the current draw of the LED circuit. Once you have that you can reverse compute the minimum resistance load you need apply to avoid hyperflash.
It may be the case that your circuit is already at the limit (8 ohms gives a 1.5 amp draw), because that's what I have done to limit the heat big time on my circuit.
You are correct in that resistor is going to get very hot and will damage the plastic around unless you protect it with a heat shield (don't wrap the resistor, it needs to be ventilated!!!!).
a++ Cedric
Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
Bingo! This is also what I told the vendor that supplied mine. My supplier shipped me resistors that were encased in heatshrink tubing. I informed my supplier that this radically cuts down on the rating of the resistor (although I don't know the exact amount). In my application, I stripped off the heatshrink to allow the resistor to radiate heat better and also made a tie-wrap system that held the resistor securely in place off of the harness by about 2 inches also.P.S. My resistors are wired in parallel to the LED bulbs.
Pro
Joined: Apr 2008
Posts: 728
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From: Paris
Get yourself a variable resistor, put the turn signal on and change the value until you get hyper flash.
turn the signal off, dial the resistor back a bit, turn the signal on to ensure that you are good.
Do this test with and without the engine running.
You now have the resistance you can use to be borderline, measure it and find the closest normalized resistor.
I would take a TO-220 type resistor, easy to cool off with the right heat sink.
Alternatively, measure the current drawn by the LED circuit and do the reverse maths.
a++ Cedric
ps: Careful for the heat shrink, it's there for a reason, water can reach it ... not good!
turn the signal off, dial the resistor back a bit, turn the signal on to ensure that you are good.
Do this test with and without the engine running.
You now have the resistance you can use to be borderline, measure it and find the closest normalized resistor.
I would take a TO-220 type resistor, easy to cool off with the right heat sink.
Alternatively, measure the current drawn by the LED circuit and do the reverse maths.
a++ Cedric
ps: Careful for the heat shrink, it's there for a reason, water can reach it ... not good!
Thread Starter
Melting Slicks
Joined: Oct 2008
Posts: 3,355
Likes: 12
From: Beverly Hills, MI
