locoboy
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| posted on 28/4/04 at 07:50 PM |
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Testing charging system
I replaced my alternator because the old one was over charging the battery, am i right in thinking i will be able to measure the output of my new
alternator by running the car and putting the multimeter on the battery?
When i rev it the reading shouldnt change should it?
ATB
Locoboy
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JoelP
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| posted on 28/4/04 at 07:55 PM |
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not sure if it changes with revs, i suspect it will slightly (the regulator cant be perfect surely?), but the difference in volts will be quite
apparent if it is/isnt working.
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Jon Ison
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| posted on 28/4/04 at 07:57 PM |
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maybe useless info but mine charges at 14.4 volts................ 12.7 from battery when engine stood.
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locoboy
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| posted on 28/4/04 at 08:10 PM |
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holey schmoke chaps that was quick.
I thought i may have had a couple of electrical gremlins with the charging system as i put a new battery on at the weekend and this evening there was
not enough juice to opperate the horn! The battery is charging in downstairs at the moment so i will hook it all back up tomorrow and see how it goes.
It may be that i left something on and it drained it but not sure what it could been.
Only time will tell if it does it again.
thanks for the info though.
ATB
Locoboy
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TPG
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| posted on 28/4/04 at 08:16 PM |
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Charge testing.
See what you've got volts wise with it all off(12+ volts said earlier is good.).Start the car and check again.Voltage should be up.(again as
said earlier.).Turn on one electric load at a time and check the alt' has adjusted and kept the charge up.Heated rear window will be the
test.............
..Which was nice..
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locoboy
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| posted on 28/4/04 at 08:37 PM |
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rear window would be a test let alone heated lol.
My normal car - ford focus is poo for that the lights dim when you put the weated front window on, and they really do dim. Thought modern blue ovals
would have the electrics bob on by now!
ATB
Locoboy
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britishtrident
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| posted on 3/5/04 at 12:04 PM |
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Before testing make sure the battery has a decent charge before testing --- as quick check if it shows 11.8 volts or more with ignition off and no
load it should be OK to test.
Also check the drive belt is tight and the the blade termminals on the alternator are making a good connection.
It is also adviseable to do a starting voltage check on the battery starting system to diagonose a dead gassing cell in tyhe battery or internal
shunt in the starter.
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(1) Start the car and allow it to idle -- at anything above idle expect 12.8+ plus volts.
(2) Rev engine to 2000 to 3000 rpm volts should rise to 1.3.4 to 14.9 depending on alternator make and size.
(3) With the revs still at 2000 to 3000 Turn on headliights foglight and heater blower -- voltage may drop slightly but should still be in the range
13.4 to 14.9 --- less than 13.1 and it ain't chargining at all more than 15 will blow lamp bulbs.
(4) Raise the revs a bit to 3,500 rpm and turn all the lights and other electrical loads off , voltage should still stay with in limmits.
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Too much voltage is likely a duff regulator,
Too litle voltage suspect slipping drive belt, brush, slip ring or dioode fault.
Voltage spikes or erractic voltage check the blade connectyors for arcing.
Alternator charging at slightly low voltage and battery goes flat suspect diode fault causing back current drain through the alternator.
[Edited on 3/5/04 by britishtrident]
[Edited on 3/5/04 by britishtrident]
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Peteff
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| posted on 3/5/04 at 01:05 PM |
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suspect diode fault causing back current drain through the alternator.
Got this on a Rover that belongs to next door. A new battery dead overnight. It was recharged and put back on to get to the shop and when we got there
the alternator was too hot to touch. We had to wait for it to cool before removal.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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britishtrident
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| posted on 3/5/04 at 03:56 PM |
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quote:
Originally posted by Peteff
Got this on a Rover that belongs to next door. A new battery dead overnight. It was recharged and put back on to get to the shop and when we got there
the alternator was too hot to touch. We had to wait for it to cool before removal.
The Lucas Magnetti- Wotsit alternators on the Rovers is particularly prone especially the smaller models.
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Northy
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| posted on 3/5/04 at 07:35 PM |
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quote:
Originally posted by colmaccoll
My normal car - ford focus is poo for that the lights dim when you put the weated front window on, and they really do dim. Thought modern blue ovals
would have the electrics bob on by now!
We've got a Focus too, and I was told that it doesn't charge at idle to improve emissions. Not sure if thats true, but thats what I was
told.......
Cheers
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing! 
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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britishtrident
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| posted on 3/5/04 at 08:58 PM |
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Focus ECU controlled alternator -- yet another can of worms.
Interesting E-OBD ECUs are also logging postion data on some cars factory fitted with GPS system - big brother can tell where you have been.
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