Isuzu Trooper Owners Club UK™

robbie y · Posted: Sat Jan 04, 2014 11:57 Post subject: Battery Voltage issue

Hi Guys

I wonder if anybody can solve a small problem I've got with my 51 plate Citation Trooper 3.0 TD.

Its not a massive issue but is a bit strange.

I stupidly left my lights on overnight a few weeks ago and had to jump my Trooper to get going. Since then I noticed the Volt meter in the car showed the cold start Volts at around 9 instead of the usual 13ish.

Starting has got worse and I have drained the battery on two separate occasions trying to get going on a morning. I decided the battery must need changing and had both checked. Obviously this was after I had driven to the garage and not cold on a morning. Both batteries were fine and both were charging fine. One battery showed some Acid bleed around the contact points so I decided to get that one replaced anyway. The following morning and subsequent mornings the car has started pretty well although I have noticed a problem which is what's baffling me.

The Volt meter still only shows 9ish on a morning but the vehicle is now starting. After a run the Voltage shows at just over 13. I have disconnected both batteries and checked them separately this morning before starting the vehicle and both showed at 9 Volts. After turning the vehicle on and letting it warm up the Voltage then rose to 13.

My question is who is stealing 4 volts during the night. I checked every light and button to make sure everything was turned off last night.

If anybody has any ideas please let me know.

Cheers

Rob

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AD · Posted: Sat Jan 04, 2014 20:24 Post subject:

Are you using the voltmeter on the dash for your reading?

Every time you switch the ignition on to check the reading the glow plugs will be robbing you of your volts.

If you change your battery you should change them as a pair the old battery will kill your new one eventually, theres probably not much wrong with your old one.

Check your fan belt tension
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2011 3.0l Hilux Invincible
94, 3.1 duty
95, 3.1 commercial, Agricultural licence
04, 3.0 citation

Browndoff · Posted: Mon Jan 06, 2014 12:14 Post subject:

You were RIGHT to check around for a light 'mysteriously' ON - it can happen as a result of a chafed wire making a connection it should NOT! The problem is that it doesn't have to be anything which would glow - or otherwise be 'obvious' to your inspection. An accidental short can occur anywhere that cables might be rubbed by something moving or themselves move against a fixed-surface - which is why all the cable-looms are tied-down every few mm!

[1] Beg, borrow or steal a standard voltmeter - and check your batteries - BEFORE you try to start in the morning. BOTH should read 12V. If NOT then disconnect BOTH after a run - check voltage - again, BOTH should read 12V disconnected - and leave overnight. In the morning, BOTH should still read 12V!
[2] Recheck with the engine at tickover - BOTH should read 13.5V or more, if the alternator is working properly. BOTH should read 14.5V, or more if you rev it up to about 3 000RPM.
[3] Properly functioning old batteries DO NOT have any negative effect on good new batteries. For instance, when I bought my Trooper, I had the 2 batteries tested ['cos there clearly WAS a fault somewhere!] and found that the newer-looking one was knackered - but the old one - with battered terminals - was 'good' and I'm still using it! One battery WILL drain the other - YES - but ONLY if one is knackered!
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2002 LWB Trooper 3.0L
I've done some major repairs, including replacing half-shaft, replacing fuel-injectors etc.

robbie y · Posted: Mon Jan 06, 2014 13:08 Post subject:

Cheers for the replies.

My neighbour has a meter which I will try and borrow and will let you know what the readings are.

AD · Posted: Thu Jan 09, 2014 7:22 Post subject:

robbie y · Posted: Sat Jan 11, 2014 10:55 Post subject:

Hi all

I've had both batteries checked and the alternator checked now and it seems the alternator is not charging the batteries enough. I don't get it though. The batteries are showing a charge of 12. something at the end of the day but in the morning they are showing 9. something. I cannot see how this is a problem with the alternator.

Can an alternator partly work? ie only charge to a certain voltage? Or is an alternator al or nothing.

I've looked online and have seen a brand new alternator for £100. Is this a good price and is it something I can do myself?

Cheers

Rob

griffter · Posted: Sat Jan 11, 2014 12:01 Post subject:

at idle when u measure batterie at terminals what figure u getting?

Gribble · Posted: Sat Jan 11, 2014 13:27 Post subject:

Did the tester give you any figures for the alt ? Like volts at idle ,1500 rpm and at full load ? Amps output under load ? Battery heavy drop test ?

Bit hard to say whats up without that info you see . The alt should make 14.4 v at idle with no load and still make 13v under full load otherwise no charge goes into the batteries.

Yes the alt can go on and off with its charge rate and a simple test is to see what volts you get at idle then turn all the electrics on and see what the volts go to if they go under 12 then its possible the alts faulty.

The reason that you see 12 at the end of the day and 9 in the morning is ( bearing in mind what AD posted bout the glowplugs ) is that the batteries hold whats called a Floating Charge after charging from the car running which will drop off after a while ,thats why any good autoleccy wont test a battery thats come straight off charge without doing a trial drop test to clear the float charge .

Thats a fair price for an alt and to change it is not too bad 5/10 spanner ability needed unless you have air con which puts it up to 7/10 spanner ability .
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2 New Troopers !

Browndoff · Posted: Sat Jan 11, 2014 18:22 Post subject:

As Gribble has said - you haven't given us enough info to say if the Alternator is good or bad - it could well be still PERFECT!

The evidence DOES point to faulty batteries. If disconnected, they should read 12V in the evening and STILL read 12V in the morning! If you left them CONNECTED to the car overnight - there can be another explanation - simply that something was left ON [or just a random short-circuit] - draining a pair of perfectly-good batteries, from 12V down to 9V.

The only way to know about the Alternator, is to test voltage [at the Batteries will do] - WHILE THE ENGINE IS RUNNING! Again, as Gribble has mentioned, it can be 14.5V at low speed and be allowed to fall to only 13V under a high electrical LOAD [like headlights] - but it should not rise beyond 16V - even at high speed - as it's controlled by the limiter-circuit.

Even at a good price for a replacement - don't rush to 'condemn' the alternator without a fair trial!
_________________
2002 LWB Trooper 3.0L
I've done some major repairs, including replacing half-shaft, replacing fuel-injectors etc.

jay44 · Newbie Joined: 17 Jan 2014 Posts: 4 Location: portsmoth

hi chaps i have another problem with my other trooper the alterntor was pumping 19 volts so i had it repaired it was just the diodes had blown fitted back on it lasted one day and volts have gone up again could someone tell me what are the feed in the two pin plug are as i think the fault is there cheers