HVAC lighting slowly flickers at idle
 

What would cause this? A bad alternator or bad battery? After driving it for lets say an hour , you really do not notice it, just at start up. If I have to replace the battery I want to put in an optima, which optima fits the best?

bump! anyone?

i will take a stab. if it was my car i would hook up my 4 channel lab scope and monitor the batt,alt and ballast supply voltage and i would look for spikes while running . i would mainly look at alt and if pushed for a guess.....voltage regulator....if they are like the old bosch they are held on to the rear of the alt by 2 screws. like any electrical problem start at the source..the batt...is it old,low on water,connections tight etc ?

Thanks for the response. The battery has been drained several times. There is water in it though and all the connections are clean and tight. But I am guessing it might not be holding a charge like it should and causeing a strain on the system, what should the battery test at voltage wise when the car is off?

depends on age,type. a brand new super duty batt might show 12.80

I believe I used a yellow Optima 49R in my 986/

I just went through this exact same scenario; to make a long story short, it was the alternator. And replacing it is a relatively simple task that takes about 2 hours if you're not the best mechanic (i.e. me).


Best,

Jon

Thanks for the reply. So that seems like a difinate diagnoses, you get to the alternator behind the seats right?

I'm having the same issue, but with all of my lighting, both interior and exterior, and I believe it's the alternator, as well.

Yes, the alternator's accessed from behind the seats. Here's a DIY from the forum which someone wrote up. May help you out and be a handy reference.


http://986forum.com/forums/diy-project-guides/24008-how-change-your-alternator.html