Replace standard indicator with LED - MK4 Focus

[DannG]

Hey All,

Has anyone replaced the standard indicator bulbs with LED ones and if so, is it easy? (Mainly for the rear but may want to do front too).

A YouTube video I found made it look incredibly complex to do…but when I looked in the boot and removed the cover, it looked like you could just unclamp the grey plastic holder and replace…..I didn’t try it though!

Thanks!

[DaveT70]

You may need FORScan to turn off bulb monitoring as you may get hyperflash

[StephenFord]

2 hours ago, DaveT70 said:

You may need FORScan to turn off bulb monitoring as you may get hyperflash

Wouldn't a CanBus LED bulb sort that out?

[alexp999]

High resistance "canbus friendly" LEDs shouldn't be a problem.

The car is just measuring the resistance of the bulb. An incandescent is high resistance as it's using heat to generate the light. Low resistance would indicate a missing or blown bulb. LEDs are much lower resistance unless manufactured with a built in resistor to give the correct reading to the car.

[DaveT70]

40 minutes ago, StephenFord said:

Wouldn't a CanBus LED bulb sort that out?

Possibly, if they really are canbus, some just say they are

[alexp999]

I'd go with one that specifcally says high resistance, rather than canbus friendly personally if you're concerned about hyperflashing or errors.

[StephenFord]

2 minutes ago, DaveT70 said:

Possibly, if they really are canbus, some just say they are

That's dreadful, to think that some retailers fib about their product 

[alexp999]

I think what doesn't help is that a lot of the LED Bulbs are cheap tat from China that UK shops sell as their own. It's hard to know what you are getting and one person could have a good experience with some decent ones on one occasion, only for the bulb to change next time it's ordered.

[StephenFord]

10 minutes ago, alexp999 said:

I think what doesn't help is that a lot of the LED bulbs are cheap tat from China...

That's the delight of running an 18 year old car, mine isn't clever enough to know what kind of bulb I put in, and it has no mechanism to warn me of impending doom! LOL

[piotrmod]

Are you interested in front or back indicators. Front are quite standard mounting  (metal cylinder WY21W) is is easy to find Premium LEDs (Philips, Osram).

Back is more tricky. They Are WY16W - flat mounting. There are no high quality, premium ones. In UK, you have your autobeam shop, maybe they have. I tried a few china s**t, some are ok but most is giving "shades" and effect is poor.

The other thing is "outage detection" (some called it CAN bus support, which is horribly insane).  If you use premium LEDs, you can easily disabled it using Forscan. But, china LEDs that is the other story. I don't trust them.

I have tested bulbs like that:

They do the best effect. However, by factory they consume almost 7W!!! (which makes outage detection works) but the light is almost white, and their lifetime must be short. I have modified them to get 1.8W which gives same light intensity as a bulb. So I don't trust them (they are made very carelessly), I had design a real outage detector, same as premium LEDs are provided with. It requires some wire connections but works trustworthy:

It simply connects additional resistor, when LED is consuming energy.

Anyway, It is complicated. Indicators are quite important from safety perspective and it is better to have them working perfectly.

 

 

[mjt]

2 hours ago, alexp999 said:

The car is just measuring the resistance of the bulb. An incandescent is high resistance as it's using heat to generate the light. Low resistance would indicate a missing or blown bulb. LEDs are much lower resistance unless manufactured with a built in resistor to give the correct reading to the car

I think you've got that the wrong way round. An incandescent bulb is low resistance, although it increases a bit due to heat once it's illuminated. A blown bulb is open-circuit and therefore infinite resistance. The car measures the current being drawn and LEDs draw much less current so appear high resistance. To overcome this Canbus-friendly LED Bulbs have a resistor connected in parallel to increase the current drawn and lower their apparent resistance.

[unofix]

3 minutes ago, mjt said:

To overcome this Canbus-friendly LED bulbs have a resistor connected in parallel to increase the current drawn and lower their apparent resistance.

Correct, and the more expensive larger LED units also incorporate a bridge rectifier so that they are not polarity conscious. Due to physical size limitations most small LED replacement units can not include the bridge rectifier and hence have to be installed the correct way around.  

[alexp999]

6 minutes ago, mjt said:

I think you've got that the wrong way round. An incandescent bulb is low resistance, although it increases a bit due to heat once it's illuminated. A blown bulb is open-circuit and therefore infinite resistance. The car measures the current being drawn and LEDs draw much less current so appear high resistance. To overcome this Canbus-friendly LED bulbs have a resistor connected in parallel to increase the current drawn and lower their apparent resistance.

It's because the bulbs with built in resistors are sold as high resistance, it threw me and flipped what I remembered 😅

[anon]

1 hour ago, mjt said:

I think you've got that the wrong way round. An incandescent bulb is low resistance, although it increases a bit due to heat once it's illuminated. A blown bulb is open-circuit and therefore infinite resistance. The car measures the current being drawn and LEDs draw much less current so appear high resistance. To overcome this Canbus-friendly LED bulbs have a resistor connected in parallel to increase the current drawn and lower their apparent resistance.

Quite right, too. Now, I have had incandescent bulbs in cars since they gave up on acetylene and in terms of reliability, they are not too bad. Modern cars tell you if they have failed and they are cheap and easy to replace. Buying an LED bulb that is correctly certified and likely to be as reliable is virtually impossible as yet so I simply wouldn't do it.

[piotrmod]

One remark about resistor. It does not bring the detection back in. It just fools up the car. In case of LED bulb failure, the car will not see it since the resistor is still consuming power. One may say, that well adjusted resistor will do, it may with H7 replacements, where a bulb itself consumes 20W. With indicators, stops etc. LEDs bring just 2-3W and taking to account that the voltage changes from 12.5V up to 15.2V adjusting such resistor is absolutely impossible. 

[anon]

Not strictly correct but the resistor needs to be quite big and needs space to dissipate its heat. 33 Ohms placed in parallel will draw c. 1/3 Amp at 12 Volts would do but that means you have four Watts to get rid of.

[DannG]

25 minutes ago, anon said:

Quite right, too. Now, I have had incandescent bulbs in cars since they gave up on acetylene and in therms of reliability, they are not too bad. Modern cars tell you if they have failed and they are cheap and easy to replace. Buying an LED bulb that is correctly certified and likely to be as reliable is virtually impossible as yet so I simply wouldn't do it.

After reading all the responses I sadly agree. Who would have thought in 2023 you can’t buy a premium branded LED indicator bulb. I mean, seriously! Ridiculous. 

[DannG]

Think I’ll scrub that idea then. Thanks all for the responses though 😀 

[anon]

There is very little money in it for the manufacturers. Incandescents are energy intensive to make but the infrastructure is there to make thousands of glass bulbs daily for pence. LED is comparatively cheap but it needs a thermal mass, a piece of aluminium for a heatsink that costs more than a whole bulb and quite a lot of processes that aren't the same so you need a new factory to service all the cars that are going to be scrap in ten years' time  that are well served by filament bulbs while the car manufacturers will be integrating  customised LEDs into their light units. It simply doesn't make economic sense.

[DannG]

2 minutes ago, anon said:

There is very little money in it for the manufacturers. Incandescents are energy intensive to make but the infrastructure is there to make thousands of glass bulbs daily for pence. LED is comparatively cheap but it needs a thermal mass, a piece of aluminium for a heatsink that costs more than a whole bulb and quite a lot of processes that aren't the same so you need a new factory to service all the cars that are going to be scrap in ten years' time  that are well served by filament bulbs while the car manufacturers will be integrating  customised LEDs into their light units. It simply doesn't make economic sense.

Did make me wonder why on a 2021 car, it has LED (OLED?) rear lights and front daytime running lights, but then standard bulbs for brake lights and indicators. So random…but maybe this is why! 🙂 

[StephenFord]

56 minutes ago, unofix said:

...Due to physical size limitations most small LED replacement units can not include the bridge rectifier and hence have to be installed the correct way around.  

I had occasion to buy a courtesy LED bulb replacement just last week (to replace an existing LED bulb, they really last no longer than standard bulbs!). On putting the bulb in, it lit up great, lucky I thought, right way round 1st time. However, I didn't locate it properly and it fell back out, when I put it back, again, it lit 1st time again. Curious, I then tried it both ways - it worked no matter what way I put it in! Unlike the one that I got a few years ago.

I guess the LED bulb suppliers use to get so many returns with people thinking they had 'faulty' bulbs, they tried awfully hard to make polarity irrelevant!