Alternator works...sometimes !

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
landowner

landowner

Pensioner Pete
Full Member
Posts
13,605
Location
WA2
Just fitted a voltmeter cause the battery was slowly going flat, took over a week.

Volt meter shows 14 to 16 amps depending on engine revs...sometimes.

Sometimes when I start her up the voltmeter doesn't get off 12v and drops when brakes applied, heater on , lights etc so not charging.

Question is, is it faulty alternator or is there a relay somewhere not clicking in.?

Not too well up on electricals:rolleyes::rolleyes:
 
landowner said:
Just fitted a voltmeter cause the battery was slowly going flat, took over a week.

Volt meter shows 14 to 16 amps depending on engine revs...sometimes.

Sometimes when I start her up the voltmeter doesn't get off 12v and drops when brakes applied, heater on , lights etc so not charging.

Question is, is it faulty alternator or is there a relay somewhere not clicking in.?

Not too well up on electricals:rolleyes::rolleyes:
Click to expand...
no **** Sherlock :eek:
 
Put your voltmeter on your battery terminals, fully charged it should read about 12.5 volt to 12.75 volt. Start car and it should go to about 13.8 volts, put all lights and heater on and rev engine, it should go to 14.2 volts ish..
 
clivesP38 said:
Put your voltmeter on your battery terminals, fully charged it should read about 12.5 volt to 12.75 volt. Start car and it should go to about 13.8 volts, put all lights and heater on and rev engine, it should go to 14.2 volts ish..
Click to expand...

Aha, sorry if I got me volts and amps mixed up, thinking of ammeter:rolleyes:

Charge light goes out every time.

Charges at over 14v with nothing switched on (battery fully charged overnight last night), drops when something switched on, with heater switched on full it drops from 14 to 12 and the needle flicks with the indicators. It is wired from the fusebox and earthed into the loom on the top middle of the dash (1990 defender):)
 
Cant have wired it back to front can I:rolleyes:?

Voltmeters are usually stable and the needle rises and falls slowly but mine doesn't,:)
 
If you have revved it after putting it under load, switching lights and heater on, and it drops to 12 v then the alternator high charge is not working and you need to replace alternator.
 
clivesP38 said:
If you have revved it after putting it under load, switching lights and heater on, and it drops to 12 v then the alternator high charge is not working and you need to replace alternator.
Click to expand...

Thought so:rolleyes:

Engine coming out next weekend so I'll have to charge battery a couple of times till then.

Took the head off my stupid diesel Saxo on Friday so relying on 90 for transport. never rains but it pours eh:rolleyes::rolleyes:
 
ideally you want an ammeter to compliment your voltmeter.

voltmeter will tell you current state of battery, ammeter will tell you whats going out of the battery or whats being put in by the alternator.
a charged battery will not show amps going in, however immediately after starting should show up to 70 amps, dropping to near zero as the battery receives a charge.
this is where the voltage will show on your voltmeter as 14.2 ish.
your issue could be low output on the alternator, although putting out 14 volts, may only be producing 5 amps. this could be caused by a defective alternator (suspect brushes) or a defective battery (suspect sulphated or a cell down)

best option so far would be a freebie halfrauds battery check, both static and running.
should give you an idea of what the alternators putting out, recovery rate of battery and state of health of battery. if they have a clamp meter (unintrusive ammeter) even betterer.
hth!
 
nrgserv said:
ideally you want an ammeter to compliment your voltmeter.

voltmeter will tell you current state of battery, ammeter will tell you whats going out of the battery or whats being put in by the alternator.
a charged battery will not show amps going in, however immediately after starting should show up to 70 amps, dropping to near zero as the battery receives a charge.
this is where the voltage will show on your voltmeter as 14.2 ish.
your issue could be low output on the alternator, although putting out 14 volts, may only be producing 5 amps. this could be caused by a defective alternator (suspect brushes) or a defective battery (suspect sulphated or a cell down)

best option so far would be a freebie halfrauds battery check, both static and running.
should give you an idea of what the alternators putting out, recovery rate of battery and state of health of battery. if they have a clamp meter (unintrusive ammeter) even betterer.
hth!
Click to expand...

Ta.
Its a fairly new heavy duty battery so I think its ok.
Had a tinkling sound under the bonnet just before this happened, like a pulley catching something and it was from around the alternator area, its stopped now but so has charging. Must be alternator.

The 200 I'm putting in has an alternator on it so fingers crossed:)
 
nrgserv said:
oh, and apologies for me first post in your thread.......
what engine you currently got in it?
Click to expand...

Ok, wasn't thinking voltmeter when I wrote it:D

Got 2.5n/a in at the moment, its coming out next weekend, 200 ready to go in and some welding to do and seat boxes coming out and hopefully a mud stuff dash or similar to go in.
Probably take me a month to sort it out but it'll be lovely when its finished;):)
 
You must log in or register to reply here.

Similar threads

dag019
Alternator failed - how to safely continue driving
2
Replies
22
Views
1K
tottot
tottot
bukko
Disco 2 TD5 - Intermittent charging
Replies
6
Views
999
Stanleysteamer
Stanleysteamer
F
External Volt Regulator
Replies
3
Views
468
tottot
tottot
R
P38 Alternator Fault
Replies
2
Views
489
Datatek
Datatek
DefendingLancashire
Major leccy issues - everything dying when rolling off the power
Replies
4
Views
385
DefendingLancashire
DefendingLancashire
Back
Top