Agriv8
|
| posted on 17/2/07 at 11:30 PM |
|
|
Alternator Voltage Dont Understand
been out and about today.
When the car is started my volt meter shows 13v.
Set off back in the dark tonight and even with lights on ( dipped ) still showing a health 12.5 v.
By the time I get home 25min thrash ( driven HARD ). voltage showing 11.5 v.
All i can think is that the alternator is getting too warm ?
It a 4 pin Nipon desno from a rover / honda any ideas or am I needing to source a relpacement.
Thought apreaciated
Regards and thanks
Agriv8
[Edited on 17/2/07 by Agriv8]
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
|
|
|
|
|
ayoungman
|
| posted on 17/2/07 at 11:47 PM |
|
|
If you put a meter on the battery with the engine running, you should see 14.4 volts if your alternator is working properly. When you stop the engine,
it should drop to a nominal 12.5 ish volts. Anything less and it means your alternator is not working correctly. It could be the pulley diameter is
too big, this would mean its not spinning at the correct speed. Don't assume the alternator is faulty. HTH
"just like that !"
|
|
|
zetec7
|
| posted on 18/2/07 at 05:32 AM |
|
|
I totally agree with ayoungman - you should see around 14.5 volts immediately after start-up (when it stabilises), 13 - 13.5 when running with the
lights, etc. all on, and at least 12.5 when everything is shut off.
I'd get the alternator tested first, to put your mind at ease - most alternator repair shops (at least in these parts) will test your alternator
free if you take it in to them. Plus, they'll be able to tell you the "break-even" RPM for the alternator - if you're idling
the unit too low (possibly due to a mismatched pulley size), you'll be losing charge, especially with lights on.
By the way, a healthy alternator will compensate for the lights being on, and should bump the voltage back up almost instantly...the voltage
shouldn't go down & stay down when the lights are turned on.
http://www.freewebs.com/zetec7/
|
|
|
stevetzoid
|
| posted on 18/2/07 at 09:50 AM |
|
|
Hi There, when you start the engine measure the voltage at the battery and with the engine ticking over you should have something above 13.5 volts DC.
ish. Stop the engine and measure the volts again. you shoild have approx 12.4 volts, ish these are only approx values if you have something near this
all looks ok, when you rev the engine up you may well see a small increase in the voltage, what I think you need to know is the output capacity of the
alternator, if when you have all your lights etc on at night your are drawing off more current (amps) than the alternator can output you draw the
remaining current from the battery thus reducing the battery voltage. Ideally work out the headlight current draw and all other electrical devices,
add them together and see what it is. Current is volts divided by resistance. A second check is when you go on a run in the day what is the
voltage with no lights etc on?. this should give a guide to where the problem lies, also are all the wiring connections good, I have seen some right
dodgy wiring in some of these cars. I will check out later to see any developments.
Regards Steve Evans.
|
|
|
PaulBuz
|
| posted on 18/2/07 at 11:42 AM |
|
|
Just a quick point on steves post, you might be better of with the equation : Current = wattage divided by voltage.
ATB
Paul
|
|
|
britishtrident
|
| posted on 18/2/07 at 12:12 PM |
|
|
Its not charging
Even older type alternators should show an minimum of 13.4 volts even when under load ie headlights on. A lot of modern cars with big alternators
and modern hitech batteries run at close to 15 volts.
First thing to check is the blade connectors at the rear of the alternator are 100% clean and making good contact.
Advise you get an Lucas-Magnetti Marelli alternator from a Rover 820Sli (4 cylinder) this will be more than big enough output wise and is the right
rotation for your engine and has a nice simple Lucas 3 wire connector.
[Edited on 18/2/07 by britishtrident]
|
|
|
BenB
|
| posted on 18/2/07 at 12:44 PM |
|
|
Yup- as previously said- alternator ain't doing what it should!!! You should get 14ish volts. 12 volts is the off-charge voltage. Is the
alternator man enough for the job- it may just be that the alternator isn't big enough for everything the car is drawing....
I wouldn't run the car as it is until you've worked it out- that battery will be getting seriously discharged if its reading 11.5v.... not
good!!! You might end up buying a new alternator and a new battery!!!
Good luck...
|
|
|
Agriv8
|
| posted on 18/2/07 at 01:28 PM |
|
|
Thanks Chaps.
It must be doing somthing as its always starts and never had to charge the battery. I have done well over 2k
I will check with the multimeter across the battery ( both cold and hot ) rather than trusting the gauge on the dash ( as It hasn't got its own
dedicated feed - just used the power feed that runs to all my other gauges - possibly thats the problem ).
So should be looking for arround 13.5 volts !!!
Intresting about the pully diameter as it as i never noted the size of the crank pully from the doner as apposed to the rover v8. whats better
slightly faster or sligtly slower ?
Will report back shortly
regards
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
|
|
|
Agriv8
|
| posted on 18/2/07 at 11:38 PM |
|
|
right checked at start-up with multimeter.
battery has 12.5 volts car starts that jumps to 14.4 ( engine running )
put main beam and fan on get it down to 13.7 ( my gauge is showing just above 12 )
so my gauge is out - so is running my Volt gauge in series with all my other gauges causing the problem.
the next thing to try
1 dedicated wire to Volt meter and test again
2 double check test when engine is hot .
any further thought chaps
Regards and thanks
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
|
|
|
jack trolley
|
| posted on 19/2/07 at 05:57 PM |
|
|
What instruments are you using?
If you're using old Smiths type they need a voltage regulator.
The old regulators are a crap design and were obsolete when Nelson Mandela was
in Borstal - replace with a modern IC regulator.
|
|
|
MikeRJ
|
| posted on 19/2/07 at 10:04 PM |
|
|
quote:
Originally posted by jack trolley
What instruments are you using?
If you're using old Smiths type they need a voltage regulator.
The old regulators are a crap design and were obsolete when Nelson Mandela was
in Borstal - replace with a modern IC regulator.
Only the temperature and fuel gauges need to have a regulated supply, by definition the voltmeter must not be connected to a regulated supply.
As well as the positive wire from the ignition circuit, note that the earth return could also be causing your problem. Trying connecting your
multimeter across the back of the voltmeter first to check that you voltmeter is reasonably accurate.
|
|
|
iank
|
| posted on 19/2/07 at 11:07 PM |
|
|
quote:
Originally posted by Agriv8
right checked at start-up with multimeter.
battery has 12.5 volts car starts that jumps to 14.4 ( engine running )
put main beam and fan on get it down to 13.7 ( my gauge is showing just above 12 )
so my gauge is out - so is running my Volt gauge in series with all my other gauges causing the problem.
the next thing to try
1 dedicated wire to Volt meter and test again
2 double check test when engine is hot .
any further thought chaps
Regards and thanks
Agriv8
If you really mean in series then yes that is wrong (not sure you actually mean that literally though), it needs to be directly across the battery
positive and earth.
Ideally a short thick-ish wire directly to the ignition switch. and another to a good earth.
Long runs of thin wire can drop a surprising number of volts.
I'd suspect a dodgy earth initially as the cause though and be the first thing to check, followed by a knackered voltmeter (clip the multimeter
directly onto it's terminals if you can).
Depending on your voltage regulator the gauge could do all sorts of weirdness if it was connected across that. The horrible bi-metallic strip ones
rely on the temp/fuel gauge being slow to react and voltmeters are fast. If it was a solidstate regulator by definition you should always get a
reading of 10v.
[Edited on 19/2/07 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
|
|
|
EVs
|
| posted on 20/2/07 at 10:24 PM |
|
|
quote:
Originally posted by Agriv8
right checked at start-up with multimeter.
battery has 12.5 volts car starts that jumps to 14.4 ( engine running )
put main beam and fan on get it down to 13.7 ( my gauge is showing just above 12 )
Those sound about right (what you measures with your multimeter)
quote:
so my gauge is out - so is running my Volt gauge in series with all my other gauges causing the problem.
Erm, it shouldn't be in series with anything, except perhaps a fuse. Basically it wants to be wired to the ignition "on" terminal
(II or whatever) and ground.
It's probably just knackered or a bit inaccurate though. Does it go pack to "0" when it's off, or is it out then too?
[Edited on 21/2/07 by EVs]
|
|
|
