Set off from work and I noticed the Dash lighting up every time I applied the brakes

My journey home takes about 3 hours and this issue only went away when it got dark and I had to turn the lights on...

The dash was lit like when you turn the lights on..I have just changed the sidelights and number plate to LED, my last set of sidelights where also LED but this never happened before..so I don't think this is the issue

All the lights on the car are working fine as I pulled over and checked

Can anyone help please

I guessin a fuse has gone mate

I'm hoping it is just a fuse mate

sounds like theres a bit of a short out somewhere that the dash lights have somehow come into contact with the brake light circuit

My headlights sometimes get brighter when I rev the engine

My dashboard also does this and has done for a while now. If you find out how to fix it let us know because its bloody annoying!

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My headlights sometimes get brighter when I rev the engine

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Mine do this when I have the heated screens on and the heater. It's only because there's more draining on the battery than normal

It's not a fuse. Fuses blowing will stop things working, not make things behave strangely.

What has happened is somewhere along the line your brake light feed has shorted with the illumination/sidelight feed. Because the sidelights and dash illumination are linked, I'm guessing there's a short or earth fault somewhere. Because its brake lights, check the rear lights.

Are these LED's you're all buying CANBUS compatible ones? I've had nothing but trouble with general LED bulbs, hence why all of mine are normal incandescent ones.

My front sidelights are led never had problems, then changed rear brake lights to led's and were also fine then one day I noticed my dash was lighting up when braking. I think it might have something to do with the crazy amount of cable splicing I had to do to get my focus submarine lights and illuminated gear knob to work.

Yeah, that might not help

I changed the interior light to LED yesterday and I noticed at night the LED is always lit ..even when the car is switched off. . . So I change it back to the old one.

When I bought the car one of the first things I did was to change the sidelights and brake lights to LED. The only problem I had was after about 3 months the sidelights started acting strange, the passenger side was flickering and eventually stopped working all together and the drivers side was only half lit...but the brake lights are working just fine..I'm trying a different brand of LED for my sidelights and so far are working..

Thinking about it I gave a friend at work a jump start just before the dash started going bonkers ...could this have caused the issue...

The interior led will go off after about 10 minutes of locking the car. I've seen that happen to led sidelights before its just because they're cheapo ones just get some more cheap easy fix

I went to Ford today to ask about the dash problem.

I spoke to the mechanic and explained the issue, the first thing he said was "have changed the lights at all" basically it could be down to the LED's not being installed correctly i.e not put in the right way round, but saying that they don't work the wrong way round? It seems to have started when i changed the side lights. To quote the mechanic "At the end of the day when you don't use the correct bulbs you can cause problems"

When I say the wrong way round, I don't mean +/-

Obviously the rear brake bulbs are tail lights as well, there are two positive feeds - one for the tail light, one for the brake light. On traditional bulbs, you have two filaments. One is a tail filament, the other is a brake filament. Because with LED bulbs, all the LED's are on one circuitboard. It's not beyond the realms of possibility that when you brake, you're putting voltage through the circuitboard which is in turn putting voltage down the tail feed. Tail feed = sidelights = dash illumination.

It could be that the Fiesta uses two positive feeds to control the different filaments, or, it could be that the Fiesta uses two negative feeds to control the different filaments. Therefore, some bulbs may be compatible when others aren't.

This is just one reason why I'm using standard lights all round (bar number plate LED's), there's just too much to go wrong.

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"At the end of the day when you don't use the correct bulbs you can cause problems"

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Weirdly, that's the be all and end all.

It's a case of finding a set of LED bulbs which don't cause problems.

I totally agree mate, I’ll be switching back as the complications are not worth the hassle.

I lot of what you said went over my head