How much amperage can an alternator support? no really...

[Vittorio Bares]

Thanks - this is good info, and encouraging.

My cooling fan is on a manual switch and I typically run it always-on
(eliminates one more point of failure in the temp-switch). Any idea what
amperage that draws?

Looks like I'm pretty close to max w/90amp - I can reduce the draw by
converting my lights to HID, where instead of using 100w per light,
they'll only draw 35w - and give better light. 

I've heard people say the alternator has to 'work harder' given the load
- I don't understand how a device on a pully system that varies in speed
based on engine speed 'works harder' given a greater draw ? Doesn't it
continuously do the same thing - but its output is regulated according
to need? Will the alternator wear out sooner the more power it needs to
produce?

Vittorio -

-----Original Message-----
From: Huw Powell [mailto:audi at humanspeakers.com] 
Sent: Monday, February 04, 2008 1:12 PM
To: Vittorio Bares
Cc: quattro at audifans.com
Subject: Re: How much amperage can an alternator support? no really...


> I've got 580 watts of lights on the rally car, this will require 
> 48amps to run. Typically the 4000 has a 90amp alternator, I know I 
> could go with the heftier 110amp alt from a 200 or what not.
>  
> But my question really is, how much amperage does the car need to run?
> The only other acc I have is the heater fan, radiator fan, a few 
> gauges and lighting for those, brake lights, fuel pump, intercom 
> system - potentially the wipers. How much amperage does an alternator 
> (typically 20 years old) really produce?
>  
> My assumption is that the big current draw is going to come from the 
> radiator fan, fuel pump and possibly the heater blower fan - but also 
> the ignition (spark, etc)...

My coupe has an essentially stock alternator, and on high beams I'm
running 400w of lights.  Car still runs and charges the battery fine
even if I turn up the 480w of stereo up real loud.

I think the FP runs about 10 A, the CIS another 10 or so, and the coil a
few.  The radiator fan might not come on much as long as you are in
motion.

I would make sure to do a few things - install a good, accurate
voltmeter (like the coupe/90Q ones), make sure your alternator/voltage
regulator is in good shape, use a good battery, and make sure all your
primary wiring and connections are in good shape.

The car will work down to about 9.5 volts or so, so if you are
overloading the alt you'll have plenty of time to do something about it
if you see the voltage running below 12.6.

--
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/