Alternator slow to start charging on wet/dewy mornings
 

Twice now when I’ve started the car (05 4.8is) in the morning after heavy overnight rain or a heavy dew the alternator doesn’t start charging until perhaps 3-4 minutes. It then works fine for the rest of the day. Any thoughts? The car only has about 70K miles so is still a youngster.

Better change that alternator... had the same symptoms and ignored... then the car had a trans fail safe, followed by complete shut down rolling half way up the verrazano bridge. Needless to say the next weekend, i was replacing the alternator......

Very good chance there is a problem with the belt slipping. Make sure the belt. tensioner, AND the alternator pulley are in good condition.

Test with volt meter at the battery posts
Idle
1500 RPM
2500 RPM

Any variation in voltage (other than a few 10ths) means volt regulator/brush failure to connect to the stator. Replacement or rebuild the original is the only recourse.

Carbon build up is the cause. when wet the connection is worse.


Mine died at 60K

Easy diy once you remove the aux fan assembly so you can see the bolts holding the Alternator and wiring.
Chance to change your belts and tensioners and idler. you have to pull the upper hose as well. See images below

Thanks for all the replies - sounds like some alternator work is in my future. Is a regulator replacement likely to enough?

Pretty sure it’s not a belt issue - I’m thinking a slipping serpentine belt would make a hell of a racket.

Mine has done it a couple of times, no noise at all until you hear it cut in when the slipping stops. No alt light though either as the voltage will be up with belt slipping. Is your light coming on ?

Should have mentioned that - alternator warning light goes out as normal. I see the issue from the voltage displayed by the Xtrons head unit and a separate voltage monitoring LED located in the ashtray,

Are you using torque pro for your display of data?

I found that changing to fast data logging works best, but if an app in the background tries to start in between logging it can hang some of the data i.e. GPS, voltage so maybe it's working just not updating...[emoji848]

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I'd give it 50/50.

My symptoms were different, I was getting 11.5 to 12 volts at idle, and a steady-ish 13.8 volts at anything above 1200 rpms. I was sure it was the voltage regulator, which I then replaced with the correct Valeo part for $75...No change in symptoms..

I ended up replacing with a new (not rebuilt) alternator..problem fixed..

alternator failures are typical on 2004-2006 N62 engines with less than 100k