Fix Blown Tail Light Problem?

[PAH]

K31TH,

 

I = V/R.  Current = 12 / 4700.  Current is a tad less than 3mA.  The resistors I'm looking at are rated at 5 watts.  12 x 0.003 = 0.036 watts which is way less than the 5 watt max.  I'm hoping that they don't run hot.

 

If I'm lucky the brake pedal will continue to trip the cruise control after I install the LED brake lights.  If not I'll try the resistors at 48 cents each (not $40 for the Error Canceller).  The guy from ledshoponline says that their globes are packed with plenty of LEDs to ensure that they pull 10 watts in an effort to overcome the issue with the cruise control.

 

I have zero interest in bling so I'd continue to use standard globes if they'd last.  I'm told that it's voltage spikes that causes globes to blow.  I'd link to know what causes the voltage spikes.  And I'd like to know why it's ALWAYS the LEFT globe that blows.  Ledshoponline advertises that its globes are also OK in 24 volt circuits so I'm hoping that that makes them more resistant to voltage spikes.

 

 

 

PAH

[bossmang]

just install them already 

Edited 14/03/19 08:46 AM by Admin (as if)

[Panda Eyes]

On 13/03/2019 at 11:53 PM, k31th said:

hmm, so these 4700ohm resistors might get a little hot... hopefully not too hot...

 

I got some of those led resistor boxes when I did the blinker led globes in my bf tail lights.

 

 

 

I mounted them on top of the rear light housing, checked a week later and they had started to melt through. plus the auto lights would always act like its night time (screen would go into night brightness mode). so I put the original blinker globes back in.

[PAH]

Panda Eyes,

 

Thanks for the info.  Is that a 6 Ohm resistor in your photo?  If so:  I = V/R.  = 12 /6  = 2 amps. 

 

The guy at Ledshoponline has advised me to use a 5000 Ohm resistor which would pull only 3mA (3/1000 of an amp).  I can't see such a high value resistor getting hot.  

He also says his LED globes have been stacked with plenty of LEDs to maximise current flow.  They pull 10 watts.  But this is still less than the standard globe that pulls 21 watts.  I dare say he is specifying a 5000 Ohm resistor for his LED globes to increase the current draw enough to trip the Cruise Control when the brake pedal is tapped. 

 

IF I need to add the 5000 Ohm resistor I don't plan to whack it across the tail light - just the brake light.  I am guessing that it's only the brake light that triggers Cruise Control deactivation.  And so I am hoping that I don't have any dramas with nightime-daytime brightness on the dashboard.

 

Admin:  I'm waiting for the LED lobes to arrive in the post mate.   If I'm lucky they will work OK without any fiddling around.

https://www.ledshoponline.com.au/

[PAH]

Guys:  A bit more.

 

A standard 21 watt should pull 1.75 amps.  I = P/V.  I = 21/12 = 1.75 amps.  If the resistor above is 6 Ohms then it will pull 2 amps which is MORE current than than a standard 21 watt light globe.  Why does it need to?  I could be wrong here, but it's my guess that the objective is to get the TOTAL load (resistor and LED) to pull the same current as a standard 21 watt globe so that the Cruise Control recognises the current draw as a brake pedal application.  If we have any auto elecs in the forum please jump in here to set me straight if I am wrong.

 

I suspect that it is a 6 Ohm resistor.  It looks a bit like these: 

https://www.amazon.com/4Pcs-Aaron-6ohm-Load-Resistors/dp/B00L4V9ECY/ref=sr_1_2_sspa?hvadid=295431745346&hvdev=c&hvlocphy=2840&hvnetw=s&hvpos=1t2&hvqmt=b&hvrand=5047983431389191575&hvtargid=kwd-396652719788&keywords=6+ohm+50w+led+load+resistors&qid=1552688817&s=gateway&sr=8-2-spons&tag=googhydr-20&psc=1

 

And this web site includes this info:  "4Pcs Aaron 50W 6ohm Load Resistors - Fix LED Bulb Fast Hyper Flash Turn Signal Blink Error Code (Resistors get very hot during working)".

 

A 10 watt LED globe should pull around 0.8 amps ( I = P / V    I = 10/12 = 0.8).   And this means (if my maths and logic are correct) then the LED should be around 15 Ohms and another 15 ohms should bump current draw to that of a standard light globe. 

 

If you have purchased LED globes and you do not know how much current they pull you can measure this with a cheap Digital Multi Meter from Jaycar:

https://www.jaycar.com.au/low-cost-digital-multimeter-dmm/p/QM1500

There is a critical issue here.  When measuring current (amps) the DMM MUST be connected in series with the LED light globe NOT across the globe.  If you're not sure of this don't even try.  The DMM can blow up if you strap it across a power supply ... if it doesn't have a fuse.  Once you know the current flowing through your DMM you can calculate power.  Assume 0.5 amps flowing through the LED.  Power = Volts x Amps.  Power = 12 volts x 0.5 amps = 6 watts.  That's less than a third of the current drawn by a standard globe.  And (I am guessing that) 6 watts may not been seen by the Cruise Control as a brake pedal application.  You can do your own maths to calculate the value of a parallel resistor required to pull the same current as a standard 21 watt globe that pulls 1.75 amps.