Alternator Voltage, Variable

[atomic-jon 1]

pre startup volatage is about 12.5v

once started the voltage starts on 14.5 volts then slowly drops to 14-14.2 volts and fluctuates between these when the car has warmed up to normal tempt indicators, wipers, brakes, sterio and headlights cause the voltage to drop about 0.2 v, also the faster the engine speed, the lower the voltage ie at 6k rpm, the volatge is about 14.1 and at 1-2k about 14.3, i know theres more load from the ignition at higher rpm....but

is this a sign of alt brush wear? shouldnt the voltage be a steady 14.5, i thought that was the diff between alts and gens in that alts the voltage is steady whatever the load and rpm

do i need a new one?

[jonah 1]

The variation you're talking about is pretty small, I expect it's completely normal. I've never tested an alternator output myself under all those conditions but knowing roughly how the regulator works I'm not at all surprised that the output varies a little bit as you vary the speed / load.

[fiji bob 0]

i wouldnt worry too much unless it stops charging the two alternators ive had from gsf both charge at different voltages one around 14.2 the other around 14.6

[Rob_the_Sparky 9]

Never looked in such detail but none of the voltages you mention should cause a problem. Bit surprised by a drop in voltage but the regulator should keep this pretty constant as long as power generated > power required but I wouldn't worry until there is a problem.

 

Rob

[atomic-jon 1]

the voltage drops to 13.5 with the headlights, sterio ect, and the battery isnt charging as well as it used to, im after a diesel alternator now...

btw when my batt +ve lead wasnt making a brilliant connection to the batt, the volatage was obvsly lower about 12.9, and also the pinking seemed to increase, ive replaced the connections but im sure if yournot kicking out the required electricity, the ignition suffers

[Rob_the_Sparky 9]

13.5V ain't great but if you are talking big electrical load + tickover then expect the voltage to drop cause not enough power is generated by the alternator at tick-over.