Alternator

[CER927]

Hi All, trying to get to the bottom of a battery issue. The optima died last summer, I have temporarily replaced it with a conventional battery. After a couple of drives out it loses charge, the alternator puts out 13.6/13.7 sometimes 14 volts. Am I correct in thinking that the alternator isn’t the problem? The alternator is noisy when the car is running, hence why I have my doubts about it. But it’s a pain changing the alternator, especially if the problem is elsewhere? Thoughts and ideas gladly received. Mark

[Penelope Stopit]

Check for a volt-drop between the alternator supply and the battery positive before going any further

[phillpot]

Does the battery voltage rise once engine started/revved a bit?

Alternator could have a dry bearing, that would make it noisey but will still charge okay until bearing fails completely.

[gruffalo]

Where are you measuring the voltage, on the alternator or at the battery, if at the alternator your 100 amp fuse could have failed hence nothing reaching the battery.

Edited by gruffalo on Monday 1st April 08:33

[Chimp871]

Just checked mine yesterday checking if I had a parasitic draw.

At low revs the battery was 12.6v if I rev the engine it jumps to 14.2v. IMO it should be over 14v under load.

You can get the rectifier/diode on the alternator fixed for cheap money if it's the problem, think I paid £30

[gruffalo]

Chimp871 said:

Just checked mine yesterday checking if I had a parasitic draw.

At low revs the battery was 12.6v if I rev the engine it jumps to 14.2v. IMO it should be over 14v under load.

You can get the rectifier/diode on the alternator fixed for cheap money if it's the problem, think I paid £30

If 12.6 at tick over then very healthy, and nowt wrong in any way, 14.2 Erving is a little high but not so high as to be a problem.