Rover 75 headlamp brightness varies

[crowthornetubes]

Hi
I have just noticed now the dark evenings are here that when I put the demister on the headlamps dim slightly and flash back to the correct brightness as tho they are connected to a flasher. As soon as the demister is turned off the lights returns to normal. Not tried it with any other items. Any ideas?:shrug:

[Jakg]

On a similar note... i've noticed that when I "bip" the horn the interior lights flash for a split second. Not noticeable with halogen bulbs, but with the LED ones you can just notice it.

It's only a flash as the horn clicks out, and you can only see it at night... wondered if it's just me.

[rrobson]

its just because there is something else consuming power from the battery, and the alternator is having to work to put the same power back in.

its the same reason why revs drop on tick over when you put the air con on, your putting extra load onto the engine.

the same thing will also happen if you set off from standing and let the clutch quite far out so the revs drop right off and the engine begins to labour. because lights are quite sensitive to current and voltage, even the smallest drop in either will show. so dont worry about it.

it may also be more apparent in the colder months when the battery struggles to hold charge due to the cold

[crowthornetubes]

Hi
It has never done it before and I have had the car 9 years, it had a new battery 4 years ago, could it be that failing again.
It starts perfectly ok.
Gerry

[rrobson]

possibly because youve never been looking. i personally wouldnt worry, and the same thing also happens when you start the car, radio goes off, interior lights dim etc etc.

if you repeat the process again, but in the next gear, or even two down so the revs are higher, i bet it doesnt do it. if your doing loads of short journeys, this will cause the battery life to reduce quicker, and if you had to change the battery after 5 years previously, you may find come next year you need a new one. all i can suggest is to run the battery this year over the winter, and if you can, take the car on longer journeys so the battery can gather a proper charge. failing that, just put a trickle charger on the battery over night once a week or so, just to make sure its topped up.