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

[John Larson]

On 2/4/08, Vittorio Bares <Vittorio.Bares at nuance.com> wrote:

>>
>> 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?
>

Running the fan all the time is a less-than-good idea.  The engine will 
never get up to correct operating temperature and tend to burn 
substantially more fuel over any given period of time than an engine 
running at the prescribed engine temperature.  Audi, and all other car 
manufacturers go to great lengths to achieve a stable temperature 
environment for their engines, mostly for efficiency and emissions, but 
also for optimum power from their engines.  You're essentially running 
in warm up mode all the time.  As for the response stating that the temp 
switch isn't meant to carry a high current load over an extended period, 
I think that's bull.  The switch operates the fan relay(s) and doesn't 
carry all that much current.  I use them in air cooled applications to 
operate oil cooler fans, and they run for hours under high heat 
situations all the time.  Back in the days of the 100LS, Fox, and early 
Rabbit/Jettas, we saw quite a few fan switch failures, and sold a lot of 
them.  I doubt I sell 2 a year now, except for the ones we install when 
we change the radiator.  Not much of a failure point.  In fact, I 
probably sell more fans than switches. 

John