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Old 05-01-2024, 06:35 AM   #1
PLP
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Location: Lansing, MI
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LED taillights and Cruise Control - where to add resistors?

So my 2003 Boxster was equipped with LED aftermarket taillights by the previous owner.
The center stop light had few light bulbs burned out, so I swapped them for LEDs as well.
Now it is very bright.

In the meantime I added CC and OBC.
OBC works OK, CC - not so much.
Finally when I activated it via Durametric, it shows up on the dashboard, but once I start the car, it will disappear.
A few times I managed to actually use it - it worked OK, controlled the speed as intended. But that was after the battery was disconnected for a while. And then, the next trip the CC would "trip".

From what I gather - and it has happened before in my other car years ago - Cruise Control dislikes LED taillights, because it does not see enough load.
Hence, resistors are needed.

Sure, I added 2 resistors (one per side) on the brake light circuit, by the light assembly. Each is 8 Ohm, 25 W.

8 Ohm resistor at 12 V would mimic 18 W, at 14 V it would be close to 25 W, so like a light bulb, right?

Still, CC does not like it.

Do I need to add another one to the 3rd brake light?
Or what? Make them larger?

Any suggestions?
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Current rides: 2003 Porsche Boxster MT (me), 2019 Bolt LT (me), 2015 Audi Q5 (wife), 2008 VW Rabbit (2.5 inline 5, MT, well, for kid... but you now, it is the 5 straight)

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