Delayed charging

[Ahsai]

'02 996. Alternator does not start charging until ~4 seconds after the engine fired up. Warm or cold, SAI pump running or not. Makes no difference.

Once it starts charging, it stays at good level 13.5~14.1v whenever the engine is running. Drive belt is not slipping. No warning lights or CEL. No codes from Durametric.

 

I noticed this behavior on the voltmeter in the dash and also verified the same from the cigarette lighter.

 

I know that some Bosch alternators have a soft-start feature where charging will be delayed up to 14s (to reduce alternator load impact immediately after start up) but AFAIK, our stock alternators don't have such fancy feature. I wonder if the regulator was replaced with one having such feature. Other than that I can't explain it. Anyone experienced this?

[JFP in PA]

Is this the factory alternator or one purchased online?

[Ahsai]

Looks like stock and even original to me. This is the best pic I have. Let me check with the previous owner for more info. Thanks, John.

 

 

Edited February 23, 2017 by Ahsai

[JFP in PA]

It is entirely possible that someone retrofitted the alternator with a voltage regulator from another brand using  the soft start feature.  These regulators are common to VW, MB, Audi, and even some Ford models, so they could have sourced a regulator not knowing the feature. Several of these brands advertise this feature, as does Denso who is big in aftermarket replacements.  Realistically, it really should not bother anything.

[Ahsai]

Yeah, that's what I tend to believe now. Won't be sure unless I remove the regulator and inspect it. I don't think I have any problem like you alluded to. I'm just curious because the soft start I saw (e.g,. on BMWs) is more like 10s+ delay and not just 4s.

[JFP in PA]

Well, with the advent of engines shutting off at every traffic light, brands like Audi, MB, and Volvo added this to their alternators in the voltage regulator section.  I really don't have a feel for how long the delay runs, but I know several of them use it.