Lights dimming slightly

[Dado 540]

Hey i've noticed that the interior lights and even the headlights would dim slightly when i apply the brake. This would also happen sometimes when im idling.

Any thoughts? Alternator

[hustler]

Battery good? My GF's car was doing that and the battery was going bad.

[lvan]

Hmm

Do the lights go brighter when you give it some gas? Like rpm?

[Dado 540]

I have replaced the battery 2 years ago. Haven't had any problems,but im gonna have to check it. E39 are sensitive to the battery that is not fully charged.

Im reading up on this on other forums and people are suggesting General Module, Voltage Regulator, Alternator, Battery...

I forgot to mention that RPMs tend to dip on a rare occation.

[hustler]

^ Oh, is that all?

I hate electrical issues. My RPM hunts a little at idle too, only after a long (couple of hour) drive though.

[Dado 540]

Originally Posted by lvan

Hmm

Do the lights go brighter when you give it some gas? Like rpm?

Yes they do

[Dado 540]

Originally Posted by hustler

^ Oh, is that all?

I hate electrical issues. My RPM hunts a little at idle too, only after a long (couple of hour) drive though.

Yup you know how it is. Everything is interconnected. If you dont know your stuff thats how shops rip you off.

[lvan]

I would test the alternator first. Just curious what kind or battery is it?

[carjoe]

Just did the alt. at 160k...I had dimming lights at idle but no other symptoms until the battery light came on one morning.

[MLue1]

Originally Posted by Dado 540

I have replaced the battery 2 years ago.

The E39 draws alot of amps, if the replacement battery was too small without enough reserve, they seems to go bad fast. Take it to Canadian tire and have them check it before doing anything else.

[Max_VQ]

Measure the battery voltage with the car running and lights on & off. The voltage should be > 14 volts.

If it is less, I would suspect the alternator. Normally batteries last 3-4+ years.

[Dado 540]

To answer Ivans question, the battery is Eliminator from Canadian Tire

Max i have ran the onboard test while driving rating ranges from 13.5V-14.1V
While parked/idling rating is 14.0V (It might dip to 13.9 but back to 14.0)

Im still gonna take it to Canadian Tire to have it checked out as Mark suggested.

[propr'one]

battery/alternator

[carjoe]

My guess is battery if you're maintaining 14v at idle.

[myndgone]

Originally Posted by Dado 540

Hey i've noticed that the interior lights and even the headlights would dim slightly when i apply the brake. This would also happen sometimes when im idling.

Any thoughts? Alternator

Mine used to do that once in a while too...

And oh....Thanks for ripping off my sig