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Poll results: Shall I install resistors in order to get my turn signals blinking frequency back to normal?
Voter(s): 1
Poll is closed Oct 02, 2021
Yes. Vehicles with increased blinking frequency are dangerous to drive and shall be banned forever.  -  votes: 0 / 0%
No. Resistors have too many downsides, and as to blinking frequency - noone really cares about it.  -  votes: 1 / 100%

[Solved] Resistors for aftermarket LED bulbs - needed or not really?


Topic starter

Just made an upgrade: replaced almost all incandescent bulbs in my elderly Mercedes with LED versions. 

Love the way they shine. Ordered relatively expensive "CanBus" LEDs, which were supposed to fool my vehicle´s bulbs control circuitry into thinking that I still have incandescent bulbs and not generating any "bulb burnt out" errors.

Unfortunately, this "CanBus" feature did not truly help: my turn signals are now blinking with (approximately) double their original frequency.

I know that adding additional resistors in parallel to the bulbs will definitely help. To be on the safe side with my upgrade project, I even ordered those resistors along with the bulbs. But now that it came to actually installing those resistors, I started having some thoughts in regard to whether or not those resistors are truly needed:

The resistors have their downsides - a bunch of them:
1) price (which I already paid, but nevertheless);
2) interference with original wiring, which decreases reliability;
3) adding extra components, which also means decreasing reliability;
4) those resistors can get truly hot, = additional risk of melting smth or even causing a fire;
5) LED bulbs consume less electricity, giving some (although small) relief to the battery and alternator. The resistors will be wasting the whole electricity saved by the LEDs on generating unneeded heat...

And the only positive thing about those resistors is that after their installation the turn signals blinking frequency will return to normal.

So my question is: is it worth it? Or should I just keep driving around blinking with my turn signals with increased frequency? Will anyone really care? Actually, such increased frequency
a) may be good for safety, since arguably it will attract more attention to my maneuvering vehicle; 
b) technically cannot be that wrong or dangerous to anyone else on the road in any way, cause it is standard blinking frequency for vehicles with not all bulbs operational - it is just that in my vehicle they all are.

So what do you think: shall I install those resistors, or shall I just continue driving with "frequency-upgraded" turn blinkers? 😉
Thanks in advance to anyone who takes his time to express his motivated opinion.

This topic was modified 1 month ago by DontKnowler
3 Answers

It's worth putting the resistors in


This is what happens when you mess with circuitry that was never designed for LED.  If it were me, I would change it all back to incandescent so it works the way it's supposed to.

What’s all the hype with LED anyway? What’s wrong with the good old incandescent bulbs?

"I would change it all back to incandescent so it works the way it's supposed to"
I would not. Especially now, when every day I am enjoying how much better my LEDs are working.

"What’s wrong with the good old incandescent bulbs?"

It is not that smth is generally wrong with them. It is just that I personally did not like the way they worked on my Benz. For example, the old interior lights were inconveniently dim. Reason: due to improper interior lamps housings design, over the years, the bulbs melted and smoked (corrupted the reflective layer of) what was supposed to serve as their reflectors. My first guess was that it was the previous owners´fault: he might have inserted more powerful bulbs than specified by the manufacturer. But no - I double-checked - it was the designer´s fault: the reflectors were just too close to the bulbs and got too hot. And the remedy would have been replacing all the interior lamps assemblies the ruined reflectors were part of - an expensive solution, which in addition to that would not have fixed the root cause of the problem: the new ones would have been smoked the same way again with time. The conversion to interior LEDs fixed the problem just fine and at a fraction of the price. Plus the LEDs increased the interior luminosity dramatically - so now I can actually find small things on the car floor at night. Problem solved.

As to the exterior bulbs, their upgrade to LEDs was largely a side line to the interior bulbs upgrade: if bother upgrading, why not do it all at once? Since the improvement potential was existent there as well. For example:

As to the turn signals, the original bulbs are notorious for their colored layer (yes, they are bulbs with some sort of orange-colored layer on them) peeling off - these pieces are then visible from the outside on the reflectors, looking just ugly. Over the years, I got tired of replacing those bulbs and having to disassemble the headlights in order to get those pieces off my reflectors.

Another consideration was, that car manufacturers explain their overall transition to LED brake lights in modern cars by saying that incandescent bulbs have a slight delay before the current is sent through them and the moment they really light up 100%. That delay is small when measured in seconds, but at high speeds it is just enough for the car behind you to go X meters (this X differs depending on speed, but is not zero), hence it can be the difference between someone rear-ending you or managing to stop close behind. So if LED brake bulbs can do it, why not give them a chance?

Then, my separate fog lights, when with ordinary bulbs inside, got so hot, that the lamps could not stand it. I dimmed them down electronically like 50% and converted to running lights, but even then they needed to be replaced every 2 years or so. Apart from their price (ca. 100 bucks for a rather primitive piece is imo too much), now they do not manufacture them any more... Now that I inserted LED bulbs in the same lights, they are almost completely cold = problem solved...

There were even more considerations than that - now I cannot remember them all and do not want to make my post to long. It is just that I wanted to point out that for me this conversion had reasons, and it worked. As to the small problem with increased blinking frequency - technically, it is not that of a problem, since I know how to fix it, it is just that I am not sure if I shall and why not just live with this increased blinking frequency. Any tangible reasons other than questionable aesthetics?

P.P.S. As to Mr. Kilmer whom I deeply respect, I can not always get his logic, although I try. At times he advises people to go on living with broken ABS systems which can cost lives. But in the same time he believes that increased blinking frequency shall be fixed - even at the cost of installing resistors which are known to be getting so hot that they can set the car on fire... Just cannot wrap my head around it... Am still thinking it over...


It's your money.