Quickie alternator question

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garyrigden

garyrigden

Active Member
Posts
367
Location
Herne bay
hi, i'm having probs with the battery keep going flat on my 300tdi disco(battery has been tested and is ok and only 3 months old)so i'm thinking it may be the alternator thats playing up. question is when the engine is running on tickover what voltage should i get across the battery terminals?
 
13.4v minimum to 14.6v maximum under load with headlights and rear heated screen switched on and revs at 2500 rpm.

Does your meter have a setting for Amps?
 
WolfyDave said:
13.4v minimum to 14.6v maximum under load with headlights and rear heated screen switched on and revs at 2500 rpm.

Does your meter have a setting for Amps?
Click to expand...

cheers. yes i have a meter with amps setting and have read another post with instructions on how to test for circuits draining the battery.
 
if you have your radio code.....follow this and let me know what the meter reading is....

Set meter to Amps
With everything switched off and no keys in the ignition

Remove battery earth terminal
Put the positive(red lead) of the meter on to the battery negative pole.
Put the negative(black lead) of the meter on to battery negative lead terminal
Take a note of the meter reading.....If it reads 0.06amps or less,this is normal and acceptable.
If reading is higher.....let me know.

Dave
 
right well i tested the alternator and its giving out 13.9 volts with the engine on tickover and 14.1 volts with lights/heater blower on and engine at 2500rpm. so i am under the impression that the alternator is ok.

i disconnected the positive of the battery and put my ammeter between the battery positve and the positive lead and my meter reads 0.19 amps
pulled out all the fuses in turn and the only difference to the reading came when i pulled the 20A aux fuse which killed the clock and the reading went down to 0.13 amps
surely this minute current drain would not flatten the battery?
the only other conclusion i could come up with is that it's the alarm draining the battery.
is it possible to unplug the alarm and see if this makes a difference or is the alarm linked in with the immobiliser and remote central locking so would it affect these?
any thoughts?
gary
 
garyrigden said:
right well i tested the alternator and its giving out 13.9 volts with the engine on tickover and 14.1 volts with lights/heater blower on and engine at 2500rpm. so i am under the impression that the alternator is ok.

i disconnected the positive of the battery and put my ammeter between the battery positve and the positive lead and my meter reads 0.19 amps
pulled out all the fuses in turn and the only difference to the reading came when i pulled the 20A aux fuse which killed the clock and the reading went down to 0.13 amps
surely this minute current drain would not flatten the battery?
the only other conclusion i could come up with is that it's the alarm draining the battery.
is it possible to unplug the alarm and see if this makes a difference or is the alarm linked in with the immobiliser and remote central locking so would it affect these?
any thoughts?
gary
Click to expand...

doh! just read i was supposed to put the meter between the earth lead :doh:and battery earth terminal. back in a min
 
well i've tested it the correct way round now and have a current drain of 0.41 amps when i connect the meter which settles and stays at 0.19 amps after about 10 to 20 seconds?
 
garyrigden said:
well i've tested it the correct way round now and have a current drain of 0.41 amps when i connect the meter which settles and stays at 0.19 amps after about 10 to 20 seconds?
Click to expand...

i think the higher amp reading when i connect the meter is due to the alarm beeping when i make a circuit
 
Could always be a shot battery...? Perhaps worth trying another, even though your is new...

Otherwise, you're gonna have to check that amperage long term!
 
Hi Gary,

Next step, leave the bonnet up, and reconnect the battery earth cable.
Get something like a housebrick or a heavy hammer to keep the bonnet alarm switch depressed.
Lock the doors using the key so alarm sets.
Remove battery earth terminal and insert meter as b4....
Meter reading will read high and then settle after around 30 seconds when the alarm has done its self test procedure.
Let me know what the reading is?
And also, does your car have the standard alarm siren fitted or the battery back up siren fitted? Siren is fitted behind the battery,mounted on the o/s inner wing.

2 wire multiplug---------------stardard siren
4 wire multiplug---------------battery back up siren

Dave
 
WolfyDave said:
Hi Gary,

Next step, leave the bonnet up, and reconnect the battery earth cable.
Get something like a housebrick or a heavy hammer to keep the bonnet alarm switch depressed.
Lock the doors using the key so alarm sets.
Remove battery earth terminal and insert meter as b4....
Meter reading will read high and then settle after around 30 seconds when the alarm has done its self test procedure.
Let me know what the reading is?
And also, does your car have the standard alarm siren fitted or the battery back up siren fitted? Siren is fitted behind the battery,mounted on the o/s inner wing.

2 wire multiplug---------------stardard siren
4 wire multiplug---------------battery back up siren

Dave
Click to expand...
tested as above and the reading fluctuates when i lock the doors and then settles to 0.19 amps. i have the alarm with the battery back up system.
going to pop round my local garage today and just get them to test the battery again.:confused:
 
If I may hijack the thread, I also have a question about my alternator and how best to test it. The car is a TD5 auto and when I'm driving it's fine, the battery works without a problem but when my foot is off the accelerator the red light comes on the dashboard, not all of the time but quite a lot and the the battery is only a couple of years old. Does it sound like an alternator problem or the battery? Sorry Garyrigden for hijacking your post :)
 
fella31 said:
If I may hijack the thread, I also have a question about my alternator and how best to test it. The car is a TD5 auto and when I'm driving it's fine, the battery works without a problem but when my foot is off the accelerator the red light comes on the dashboard, not all of the time but quite a lot and the the battery is only a couple of years old. Does it sound like an alternator problem or the battery? Sorry Garyrigden for hijacking your post :)
Click to expand...

Hi Fella.....Get your battery tested first before you do anything else.
 
confucious say 'man who has knackered diode on alternator will have flat bettery in morning'.

confucious also say 'man who diconnect battery at night and reconnect it again in morning can tell if problem is with battery or car'.
 
ratty said:
confucious say 'man who has knackered diode on alternator will have flat bettery in morning'.

confucious also say 'man who diconnect battery at night and reconnect it again in morning can tell if problem is with battery or car'.
Click to expand...

can you tell me where the obd|| socket is and does it have can-bus?

roman-chariot-copyright2.gif
 
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