Scorpion34

I've been gradually replacing the bulbs in my car with LEDs. I Have most of the interior done & started moving to the exterior. I have LED turn signals in the front & rear & those work great. But seems like if I try to replace any other tail lights something goes wrong & I end up getting errors even though the bulbs I've bee getting are CANbus or "Error Free". IThe most noticeable was when I tried to replace 2 or the lower parking lights on each side. It's the lights that light up continuously at the bottom of the tail light housing when you turn your head or parking lights on.

They worked fine until I would put the car in reverse triggering the reverse lights (which were stock bulbs), & then I would get errors like crazy & all the "red" tail lights would start randomly blinking! Even the right turn signal would start fast blinking when I turned it on like I had a light out.

I don't understand, if the bulbs are CANbus they should work fine right? Has anyone ran into an issue like this before just replacing bulbs? Should I change the fuses or something? This is really weird & irritating.

shan

The interior lights do not have to be canbus compliant. You can use either stock or led bulbs.
But the exterior lights are controlled by canbus. The quality of your canbus compliant bulbs may be questionable.

Scorpion34

I figured the interior didn't need to be Canbus but I wanted to give all the information. How can I tell if the bulbs are good?

slammer111

If the bulbs don't throw an error then they're good.

The problem is that I would imagine every car manufacturer has a different minimum current threshold for each bulb, the specs for which the LED bulb manufacturers won't have access to unless they physically test every vehicle model with out there. Even then, there may be variations between different model lines. For example, something that works on a W203 C may not work on a W204 C, or a E90 3 series.

Then there are weird electrical issues too, such as (for example) many W203s cooking their license plate bulbs repeatedly due to voltage spikes. MB had to release a set of resistors to solve this problem, but only certain cars needed this fix.

Almost everyone I know personally who has fiddled with LED retrofits (including myself) finds that the results are hit or miss. My only advice is to buy from vendors that have a good warranty period, as well as a satisfaction-based refund policy. Personally I've stuck to old school bulbs for the exterior for this reason.

Chado

@Scorpion34 , I just bought a pre-owned 2011 W204 and about to endeavor the same thing you are. Can you share the brand/link to the bulbs you purchased so we know which ones didn't work for you? FWIW, I installed these on mine for license plates and have had no issues so far. https://amzn.to/3a05O5V

AZN Optics

Our LEDs work fine for w203 and w204. Lots of references. Error free and tested against multiple MB control vehicles. Also, even though the interior will not throw error codes, you can still benefit from canbus enabled units. It takes very little power to light LEDs. If you have energized lines or power leakage, it can cause your LEDs to light up, even if switch is off. There are many reported issues on that so just search the forum. With canbus LEDs, the built in resistance helps prevent this edge case. Just something to be aware of.

Chado

Thanks, will check out your site.

Scorpion34

Yes. Once I have finished this venture I will make a thread detailing which worked & didn't work for me.

Scorpion34

THANK YOU!!! I can't believe it took me so long to order from you guys! I just put your brake light bulbs in & they work like a charm!

slammer111

Just a random bump for those who want to install aftermarket LED bulbs. Getting the car to not display a Canbus error is quite simple - the circuit in question only has to draw enough current to keep the car happy. The process I used works on any circuit, such as the rear license plate bulbs.

With the knowledge gained from that exercise, it was time to tackle the reverse lights. The stock coupe setup is completely useless - I couldn't see a damn thing when backing up in the rain at night.

The product I used was a pair of VLEDs 1156 high output, which were the brightest P21W/1156 product I could find online. This product has a rated output of 1500 lumens per bulb, compared to 336 lumens for a stock P21W incandescent bulb. Another major advantage of this product is that the LEDs are located in the "correct" location (ie the same spot as the stock P21W/1156 filament) so the light pattern is the same. Personally I went with the 5000K option which is basically pure white. They also sell a 6000K variant which has that ricey bluish tinge.

***update*** Turns out this product does not need resistors for some reason. Direct plug and play. Long story. However I will leave the procedure and calculations below. Hopefully the information if helpful to others. The process still applies to any circuit that throws an error.

The electrical system voltage for my car is 14.0V when the engine is idling, and 12.5V with the car switched off. A typical battery will be between 12.0 and 12.8V. I used 14.0V for my calculations since I would be only be using the reverse lights while the car was on and the engine RPM was low. The use case matters because a given resistor configured to work when the engine is running may not draw enough current when the engine is off (such as the license plate and trunk cargo bulbs), and one selected when the car is off may draw too much current when the car is running.

The VLEDs product mentioned above draws 1.08A initially but drops to 1.03A at steady state after a few seconds (tested with a multimeter). Using 14.0V for the calculation, the bulbs draw 14.4W at steady state. Since the car expects 21W on this particular circuit, the resistor needs to draw about 6.6W. Using Ohm's law, the required resistance is 30 ohms.

I used a pair of 10W 27 ohm resistors, but if I were to do it again I'd probably start with an initial guess of 33 or 39 ohms. A higher resistance value would allow the resistors to run cooler, and the cutoff for triggering an error for this circuit is probably somewhere around 18-19W (ie +/- 10% or some tolerance value that only MB knows), though I didn't check. I would also consider using 15W or 20W resistors, though they would definitely be more bulky. Using a larger resistor is definitely recommended for applications where the bulb is constantly on, such as fog lights or low beams.

The next trick is to add the resistor in parallel. This is actually not too difficult. Look at the bulb cradle (the plastic "cartridge" that holds all the bulbs) and see which pins are connected to the reverse bulb socket, then trace it to the corresponding wires in the harness. There will be 2 wires. On my car both the L and R reverse circuits use purple/grey wires (with a different coloured stripe) for positive, and brown wires for negative. Use wires that are thick enough handle the required current (in this example I'd need something that can handle 0.5A), but don't go overkill or you may run into problems if you use my (reversible) installation method below.

I had another W203 wiring harness available so I used a set of colour matching wires, but any colour wiring will do. For the 99% of you out there who don't have an extra harness kicking around, I would recommend using red and black wires for the positive and negative leads on the resistors.

I used a twist-on connector (aka marette) on one end of the resistor and soldered the other end, but if I were to do it again I would use marettes on both ends. I would also consider using some heat shrink on the exposed ends.



Some people may prefer to use wire taps, but I didn't want to cut into the wiring. Instead, I opened up the harness connector. This is done in 2 stages. On the plastic connector (ie the thing that holds the 6-7 wire ends) there is a plastic stopper "flap" that has to be popped open with a screwdriver. From there, each individual wire connector can be slid out, with the help of either a specialized tool or a paper clip. There are 2 tabs per wire connector, one on each side (on the "up" and "down" sides) which need to be depressed simultaneously before the wire connector will jiggle out of the harness connector. I inserted the corresponding wires into the loose metal wire connectors, then slid the wire connectors back into the harness connector. I found that the added wires fit very tightly inside the corresponding holes, and there is no chance of them coming loose.

I then tied the resistors to the harness with some pieces of wire.







The same electrical principles (Ohm's law) can be used to size the resistor for any other LED bulb product, on any other circuit (eg brake lights, turn signals etc). Use a multimeter and (12-14VDC) power supply to determine the actual current draw of the product, then calculate the required current draw through the resistor.

sasagrey

To use xenons, you need a lighting assembly that's designed for xenons. Switching to xenons will require the entire lighting assembly to be replaced. My BMW xenon lighting assemblies cost about $1200 per side; they're not cheap. They don't include the xenon bulbs either, which cost about $90 a bulb. According to DOT regulations, keep in mind that there're no legal options to switch from halogens to xenons. Dealerships will not perform this job either. I think they don't let you perform it yourself because it's not as easy as it may seem. I once got some type of lights from lightingandsupplies.com and completely destroyed some of the mechanisms trying to put them myself.

tjts1

Twist ties, household twist on wire connections and exposed 12v terminals. Are you trying to set your car on fire because this is exactly how you set your car on fire. You've got to be kidding 😅

slammer111

That was the test setup to show how the wiring can be done. Some shrink wrap and zip ties can be used as well if one desires. I was still playing with the resistor values when I took the photos. The resistors themselves aren't heavy at all. Honestly I don't see why wire ties can't be used. Shrink wrap and soldered connections are the way to go if one wants something more robust.

Personally I was more worried about the resistors getting too hot and possibly melting something. That's what I didn't like about a lot of the turnkey resistor "error cancellers" sold online. Most of them have a resistance that is much too low (some 6 ohms), which is why they have to be attached to the bodywork. I found 30-100 ohms ran much cooler while still doing the job. Of course, it would've been best if MB simply posted the required values to take all of the guesswork out.

kakemuchi

Probably the quality of your bulbs is not the best? Technically, they should work just fine, without throwing any errors. Maybe you can check the quality with an expert instead of jumping to conclusions or before changing fuses and potentially breaking something. Maybe just try a smart bulb instead for less fuss. That's what I opted for in my car, and the bulbs work perfectly fine! So many functions, totally aesthetically pleasing, and super practical. Since purchasing and installing the lighting system, I've had no troubles or errors with the bulbs. I agree that LEDs can look really cool too, but most of my friends always seem to have trouble with them.

slammer111

For these cars it’s all about sufficient current draw for the exterior bulbs. Has nothing to do with the bulb quality so to speak, assuming the bulb hasn’t failed. The problem most of us face is that the new bulbs are too “good”, as in they are too efficient.