Alternater voltage

Post Mon Mar 06, 2006 9:29 pm

can anyone tell me what voltage i should be getting from my alternater to put a good charge into the battery. At the moment i am having to change my battery over every couple of weeks and when i checked the voltage with a running engine i was getting 12. 3 volts, even at high revs with or without lights on, is this right?

Post Mon Mar 06, 2006 9:37 pm

A good alternator should chuck out between your figure and 14.4v across yer battery.. that figure is good enough to put charge back into yer battery...

If you load up on everything..i.e lights,wipers,highbeam..does it drop below 12v?... if it does youve got a dodgy Alternator..

Ive just put a second hand one in and i cant even get it to read 12v let alone 12.5 like you.. so my battery will be dead in no time.

Max i can get is 11.4-11.6v across the battery..

Just to double check i put an old TestTune gadget my old man had to test it..it has a red bar for below,green for normal and another red bar for over charging... on about 1500-2000rpm it was on the bottom part of the green..soon as i loaded it it dropped below green but not as far as the red..

manual says''

below green or in red= alternator is f**ked!

Post Mon Mar 06, 2006 9:40 pm

Oh and in your case..if your having to change yer battery every couple of weeks when yer alternator is chucking out over 12v back to yer battery then sounds like you have a power drain somewhere,or you could have knackered batterys that arnt holding a charge anymore...are they new?

As for yer drain, common sence tells me to check yer Earth cables for wear on yer battery and also from below yer AFM meter to yer oil pickup..you cant miss it,its a big thick bit of cable attached to yer bodywork..they only need to be fraid to mess up yer earth

Post Mon Mar 06, 2006 9:48 pm

it seems like i'm getting 12.3 volts dosn't matter what. If i give it a jump start and then run it for a good few miles i will only get the engine to turn over half a dozen turns before its flat again. it seems like it not charging but no warning light coming on, (accept when the engines off).

Post Mon Mar 06, 2006 10:43 pm

alternator belt tight? if it is, does sound like alternator ?
warning lamp can behave like thus with dodgy charge output.

Post Tue Mar 07, 2006 5:27 pm

yes alternater belt was new recently cos it was well worn, checked last night for tightness, all ok. I will be checking for earth leads tonight but i think it is pointing to the alternater. Are they very dear? its for a 2.5.

Post Tue Mar 07, 2006 5:33 pm

12.3v is not enough, it should be higher, above 13v at least.

Post Tue Mar 07, 2006 5:41 pm

koos i think i,d have to agree there, it does seem that if i do mostly daytime driving it can just about keep the battery topped up, but if mostly nightime driving a fully charged battery would die in a week.

Post Tue Mar 07, 2006 5:42 pm

Check it at the back of the alternator aswell and across the battery, if there is a huge difference then you have a voltage drop in the cable.

Post Tue Mar 07, 2006 6:17 pm

with the engine running you should get at least between 13.6 and 14.2 volts across the battery.

check you are getting it at the alternator plugs like mentioned, if not then you have found the problem!

Post Tue Mar 07, 2006 6:54 pm

thanks everyone i will try this tomorrow night and post my findings.