Hi. 

I picked a 2020 fiesta last week. 

The dealer has said they will book it into be repaired but I was wondering if anyone else has had the same issue And knows of a fix.

Drivers side drl is dull and yellow. Passenger side is dull yellowhat bottom white at the top. 

 

 

 

 

 

 

 

 

 

 

Generally speaking, white LEDs go dull and yellow through overvoltage. There ought to be current limiting resistors in the circuit and these may be faulty. I expect that you will be needing new headlights.

Ideally, for white LED's, they would be driven from a constant current source rather than from a voltage source and dropper resistors...

55 minutes ago, anon said:

Generally speaking, white LEDs go dull and yellow through overvoltage. There ought to be current limiting resistors in the circuit and these may be faulty. I expect that you will be needing new headlights.

would you think replacing the module sort this if this was the problem? 

just thinking £35 ish on ebay as a test might be worth a shot 

 A constant current circuit will have a sensing resistor which is used to limit the current. If it goes short or is shorted by somebody wanting a bit more brightness and thinking they know what they are doing, the LED will no longer emit enough yellow light to excite the phosphor that turns it white and over a period of time becomes a DED.

The damage will have been done so I wouldn't be changing modules, I would be putting the problem into the hands of somebody who will mend it under guarantee rather than run the risk of being accused of fxxing it up myself.

Indeed you are correct, there will be a sensing resistor in series with the driver circuit which provides the sense voltage which the driver uses to control the current. It would most likely be located within the driver module (that's where I generally put them on the current source circuits I've implemented) so its unlikely anyone would short this out unless they are a dab hand with a soldering iron and can manage to get into the module...this is  likely sealed and potted anyway. I also find resistors tend to go open circuit rather than short circuit but that's not to say they cant.

I would agree that the OP should let the dealer sort it particularly as its still under warranty. I believe they are a sealed unit so changing the complete headlight will be the only course of action anyway.

 

It is largely dependent on the type of circuit. An airfield lighting system I designed some years ago used offboard current sensing resistors but I have also integrated them in conductive ink for temperature controlling some very expensive laser diodes around the dies themselves. This could have been some clever ***** trying a direct lead from the battery to light the DRLs up for some reason best beknown to itself and the evidence is clear to see.

I suspect in that case the LED would quickly go from yellow-to-red-to-orange-to-black...with plenty of smoke thrown in to boot 🤣

Depends on how long it was connected and how thick the connecting wire was. They survive, although mortally wounded if the electrons can only get through in single file!

Hi the issue is the LEDs burn the plastic strip that they light up. The solution is to take off the module and use a dremmel tool to drill out the burnt plastic. I'm having to do this every 3 months or so. It's a really badly designed DRL. I hope whoever the person is at Ford that designed this has lost their job. It's also a pain to put the headlight back in. When my car was under warranty Ford tried to accuse me of breaking it. They replaced it twice. Hope that helps!