Interior Light Behaviour

[Jamesf1]

When I open the doors on my 250, the main interior lights come on, but they seem to flicker - both have only just started doing this with the door open. Once in the car, door closed, and they are manually switched on, they come on 100%. It seems like the flicker is deliberate behaviour with the door open..?

[johnatg]

Have you got LED bulbs? The two outer bulbs are brightened gradually, I think by feeding them with a gradually increasing voltage. This seems to cause LED bulbs to flicker.

But if they flicker continually it might be because the bulb contacts are a bit weak and need tightening up, or the contacts are dirty.

Look for a guide here or elsewhere on line to check how to access them - and use plastic trim removal levers if you don't want to mark the housings.

My theory, anyway!

[Jamesf1]

Thanks for that.

Not sure about LED bulbs, I'll check my handbook.Seems odd its happening out of the blue both front and back lights though.

[agent_dess]

My LED ones flicker..fitted them a few weeks ago.. found it it annoying at first but no accustomed to the flicker.

Only flicker when they fadein/fadeout.

The old normal bulbs never did that

[PhilipK]

Could it be the switch in the driver's door not making good contact?

What happens if you open the passenger door?

[Jamesf1]

the front flickers with either door being opened - the rear flickers with either door being opened.

[agent_dess]

Sounds like you have LED lights in your car..

The front dome has 3 bulbs.. 2 will fade/flicker away so that only 1 light remains

The rear dome has 2 bulbs.. 1 will fade/flicker away so that only 1 light remains

[Mouser]

Have you got led bulbs? The two outer bulbs are brightened gradually, I think by feeding them with a gradually increasing voltage. This seems to cause led bulbs to flicker.

But if they flicker continually it might be because the bulb contacts are a bit weak and need tightening up, or the contacts are dirty.

Look for a guide here or elsewhere on line to check how to access them - and use plastic trim removal levers if you don't want to mark the housings.

My theory, anyway!

Odd, although other posts support you.

A capacitor & resistor in the right place would be the obvious way to resolve this. LEDs respond to variations in input voltage much more quickly than incandescent lights. If there is a serious debouncing issue with the switch then it's fixable, but it would be good to scope what's going on first. The switch debouncer circuing in that link should give you a good start for a few pence in parts.

[johnatg]

I'm sure it's not switch bounce - it happens over too long a period. Gradual fade of interior lights is a common feature, especially of 'upmarket' cars.

I would guess the fade is done by voltage stepping and cutting internally in the body control ecu and may be one reason why LED interior lights are not fitted as standard. It's a curious clash with the map lights and the gear change illumination.

Have they worked out how to do fade of leds with more recent cars or do they still use incandescent bulbs?

[Mouser]

I'm sure it's not switch bounce - it happens over too long a period. Gradual fade of interior lights is a common feature, especially of 'upmarket' cars.

I would guess the fade is done by voltage stepping and cutting internally in the body control ecu and may be one reason why led interior lights are not fitted as standard. It's a curious clash with the map lights and the gear change illumination.

Have they worked out how to do fade of leds with more recent cars or do they still use incandescent bulbs?

LED fading is simple enough to achieve. I can connect up my arduino to do it smoothly, or use a pot and hamfist the same result. If, however, there's a voltage stepper which has gaps between v1 and v2 then it's essentially the same challenge as debouncing, even if it occurs over the course of a few seconds rather than a few hundredths. Scoping the wires would tell you exactly what's going on, but generally speaking even a cap in parallel with the legs of the LED would solve an issue like this adequately - still behind the current limiting resistor so that you don't get a spike, and enough to power the LED for 1/10th of a second or so without obvious droop.

[Jamesf1]

Thanks for the responses. This has now stopped happening on its own. Due the the intermittant nature Im thinking its temperature related. After a spell of temps around zero its now a few degrees above, and has not occurred for a few days. Ill keep an eye out for it, but to start, be intermittant then stop does roughly tie in with the coldest days, so Im going to monitor the behavoiur vs temp.