alternator output, voltage

lain · 22-04-2009, 06:43 PM

Hi

I was only seeing a fraction over 12v on the voltage gauge while running and as a result checked the voltage directly from the 496ho alternator and at idle it's just putting out a bit over 12v. As the revs increase at the alternator it goes up to 14v which was expected but after a while of running I noticed the volts gauge was showing slightly under the 12v but it never shows more than 12.5 anyway.

Just wondered what the voltage should be from the alternator and the gauge while running, haven't checked amps yet.

i might connect my electric meter up and tape it to the dash so I know exactly what's what while underway.

My fear is the alternator is not working as well once it's hot but I'll have to check.

This all might be a paranoid me, but I'm relying on it so want to be sure.

One thing I will say I'm draining ONE battery a bit with some onboard stuff at the moment and wondered if that could be effecting the voltage showing on the guage.

cosworth mirage · 25-04-2009, 01:13 AM

alternaters correct regulated voltage is 13.7-14v.
the nearer the batterys are to the alternater the better the output will due to the lower voltage drop (12v travels very badly over distance after 15-20ft evan with large cables charging will be very poor the alternater will be sensing 14v at terminal on alt but battery may only be at 12v)
poor cable condition or high resistance will compound this

check drive belt tension
check all connections on alt and batterys and isolaters
large cables often show good low resistance on a meter but perform badly under heavy load
renew cables if any doubt using tined copper fine strand heavy cable and crimp. and heatshrink with glue lined shrink (or take to elec factors they will do it for you
get batterys tested with new type battery tester
battery if there over 5 years old renew unless they are real high quality spiral etc (battery quality has deffinatly gone downhill over the last decade with lots of cheap rebadged crap going round)
crap batterys will kill your alternater.

hope some of this will help...