pointy
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| posted on 12/8/08 at 03:54 PM |
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Testing alternator
All,
How (and I know there will be lots of tutting) do I check my alternators output using my newly aquired Multimeter?, and what should the output
read...
Then Once/if that is ok is it simply a point of touching the terminal on the battery (pos and Neg) and ensuring the battery is receiving 12volts.
Lay-mans terms is fine
Andy
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Paul TigerB6
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| posted on 12/8/08 at 04:02 PM |
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Check the battery voltage before starting the car. The voltage should be a bit higher than this when you start the car up - probably go from about
12.8V up to around 13.8 - 14 volts with the engine running
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BenB
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| posted on 12/8/08 at 04:04 PM |
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Put the multimeter onto volts reading.
Attach the clips to the battery terminals.
Normal readings would be as mentioned (ie 13ish fully charged engine off, going down to 10v (ish) when cranking, going up to 13.8-14v when charging...
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02GF74
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| posted on 12/8/08 at 04:12 PM |
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^^^ wot he says.
now in layperson terms:
1. ensure multimeter is set for voltage reading, scale to be 20 V.
2. ensure red and black probes are connected correctly to multimeter.
3. touch black probe on battery negative (labelled -)
4. touch red probe to battery positive (marked +)
5. read voltage off multimeter display.
For a healthy and charged battery you would expect at least 12.5 V.
Start engine, blip the throttle so that ignition lamp, if fitted, goes out and repeat steps 3 to 5.
this time you would expect to see around 13.5 V or as high as 14.0 V.
^^^^ and wot he said too; you gotta type quick on this site!!! 
[Edited on 12/8/08 by 02GF74]
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pointy
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| posted on 12/8/08 at 04:25 PM |
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Thanks all,
Got 12.8 with battery off of car
Will now fit battery and try when running.
I love this site .
No ridicule or titters just Cos I is fick
thanks again Off to test.
Andy
[Edited on 12/8/08 by pointy]
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pointy
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| posted on 12/8/08 at 04:55 PM |
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Help,
Car running showing 12.3 volts,..
Now if I put pos lead from meter on large terminal on rear of alternator and neg on smaller terminal should i see an output from the alternator and
should this also be 14v ish ?
Also Small red wire from rear of alternator goes to cut out switch should this not go straight back to positive side of battery?
Andy
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theconrodkid
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| posted on 12/8/08 at 05:55 PM |
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just go red to+ and black to earth for output voltage on battery,if its not getting up to 14 ish volts check at alternator output term (big wire) and
check again
who cares who wins
pass the pork pies
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02GF74
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| posted on 13/8/08 at 08:33 AM |
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quote:
Originally posted by pointy
Help,
Car running showing 12.3 volts,..
Now if I put pos lead from meter on large terminal on rear of alternator and neg on smaller terminal should i see an output from the alternator and
should this also be 14v ish ?
Also Small red wire from rear of alternator goes to cut out switch should this not go straight back to positive side of battery?
Andy
this was explained in my post. to measure alternator output with engine running you measure voltage across battery 'coz that is what the
alternator should be connected to.
I don't know about your coloured wires nor can advise with any confidence regarding the big/small terminals since would you believe, there is
more than one type of alternator, and you do not say what make/model it is.
I will make a guess from the details you have given it is a Lucas type.
On the rear will be a slot where a connector goes and there are 2 wide 7.9 mm spade connectors - these are joined together and a smaller 4.7 mm
spade.
The 4.7 mm spade is for the ignition lamp. One end of lamp connects to positive terminal of battery via the ignition switch, the other to this
spade.
Either one of the larger spades, or both, can be connected to the postive terminal of the battery; usually this is done by connecting to the starter
solenoid terminal as it is more convenient as there is a screw post there.
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