Add Capacitors or Not to Add Capacitors?

Posted by Steven O. on 14th Mar 2019


Do I need to add capacitors to my HID or LED installation?


As a first step; without all the jargon and terminology, if you install a HID or LED Conversion Kit and both sides flicker and/or a BOW (Bulb Out Warning) presents consistently then you should add a set of capacitors. If you add capacitors and the once flickering kit suddenly stops working they are plugged in upside down. Connect them in the reversed position and the kit should light up flicker-free. 


Flickering versus Flashing or Strobbing...

Not all flickering is created equal...often times strobbing or flashing can be mistaken for flickering when in fact it is not caused by the same CPU issue. If your newly installed HID or LED kit works when the vehicle if off but flashes, strobes and/or shuts off when the vehicle is on then you need resistors not capacitors.

Keep in mind, capacitors and resistors wash out the effects of the other so they should not be installed together. 

CANbus Equipped CPU

Commonly equipped on 00+ European makes like BMW, Mercedes-Benz, Mini, Volvo etc...A Controller Area Network (CAN bus) is a robust vehicle bus standard designed to allow micro-controllers and devices to communicate with each other in applications without a host computer.

As it relates to HID and LED conversion what is important is that the headlights communicate with the CPU in regards to operation. In laymen terms, the CPU is checking the return signal or return electrical signal and when it senses the HID or LED kit which are more efficient that halogen it registers a fault which triggers programmed fail-safe measures which pulse the headlights which manifests as flickering. For more details, check out Blog Article: What is a CANbus CPU and Do I need a CANbus Certified Lighting Solution.


It is important to remember that capacitors are not components designed or intended to cure all flickering regardless of the reason it presents on a HID or LED kits. Rather, a capacitor is simply one a good first step when flickering is encountered. For more information or help please contact OPT7 support!