Battery Discharging/Charging sporadically.

[Jon Bromell]

Hi Guys,

I recently purchased an '04 L200 Warrior from a private seller, and it has a peculiar electric problem that I hope you all might be able to help me get to the bottom of;

Within a day or 2 of the acquiring the truck I noticed the battery was losing power while driving, and the warning lights for Battery and Fuel filter would randomly blink on and off. It was suggested on the L200 forums that this is likely the alternator, which I believed was confirmed when one day the battery charged to over 16v (There is a built in Voltmeter on the dashboard of these trucks).
I promptly changed the alternator for a brand new one, after that the battery leveled at 13.5v so I went for a drive for about 30 miles. While driving I noticed that the Battery had reduced back down to 11.5V, then on the way back home it completely flattened. I tested the battery and it was blown, presumably from the overcharge from the previous alternator so I changed the battery out for a brand new one. With a brand new battery and alternator, it would sit on about 11.9V all the time no matter what, unless I turn on a power drainer (Lights/AC etc) then it drops rapidly as if receiving no charge at all. Someone then suggested checking the alternator relay, which I have replaced and again no change.
Yesterday, I noticed in the morning that it had discharged over night from about 11.5 to 10.5v, which oddly was enough to start the truck, but within 1 minute or so I lost all electrics (tachometer flattened, SRS light and battery light came on) (presumably the power required to turn the engine over flattened the battery) but 30 seconds after everything came back on AND the voltmeter climed to 13.5v again, but as soon as it reached this it drained back down to 11.9v. By the time I got to work (about 10 miles) it had dropped back to about 11v. After I finished work it wouldn't start due to battery now being completely flat without the truck moving once, and attempting to jump it with a large van lead to the battery hitting about 10.9v but refusing to go any further (not quite enough to start).

This morning I have taken the battery out and stuck it on a plug in charger for while I'm at work to give it some life.

Can anyone think of anything that might be causing this, I don't have enough experience to diagnose/troubleshoot much further by myself.

Thanks everyone,

Jon

 

[Rodders099]

Hi Jon.
1st thing to do is fully charge the battery and then have it load/capacity tested.
Having a battery showing 12V is not proof it is in good condition. A capacity/load test will see how it performs with a full load placed on it.

If the battery is proven to be fully serviceable, then the alternator needs to be checked.
Simply put the battery, which you now know is fully serviceable back on and voltage check it with the engine running.
Applying the throttle, the battery should charge at anything upto 15/16v.
If the battery is doing this, then the alternator is working fine. If not, then either your alternator windings are faulty or the diode pack inside the alternator has failed.
If the battery and alternator are proven to be ok.
Next thing to check out is that you haven’t got a huge earth fault in your electrics.
This is much harder to fault find, but as a quick check, with the engine switched off, put an amp meter clamp around the battery cable and see if it’s drawing and large current. This will obviously drain the battery whilst the car is not being used.
Also, remember that if you have an alarm, there will be a small current being shown for that.

Hope this helps a little.

 

[Jon Bromell]

Thanks very much Rodders. I have the battery charging at the moment, so I'll be sure to load test it before putting it back in.

Just a couple of questions;

If there is a severe earth leak, wouldn't the alternator test fail anyway as the voltage will be dropping as fast/faster than it is rising?

Can you recommend what size amp meter I will need to test for an earth leak, I'm guessing my little multi-meter won't cut it?

When checking for an earth leak, should I have the ignition off as well as the engine, or turn the ignition on?

Lastly, do you have any recommendations for where to start with finding the earth leak if this proves to be the issue?

Thanks again,

Jon

 

[Rodders099]

Hi Jon.

It should actually be called a chassis earth fault.
Some how there is a short between positive and the chassis, normally due to a cable rubbing through insulation and touching the bodywork somewhere, pretty common fault and will drain the battery constantly which also leads to the battery becoming unserviceable over a longer term due to being constantly drained and left like that.
Vehicle batteries don’t like that much.

A chassis earth fault would have zero impact on the alternator.
When checking for earth leakage, the engine should be switched off, as you are trying to see what if any current is draining your battery whilst the alternator is not present to recharge it.
Also, you may only be looking for mA’s, not necessarily A’s.

To find an earth fault, you could start by pulling out fuses until the earth leakage disappears. That should indicate which wiring circuit the fault is on.
Fingers crossed.

 

[Rodders099]

Ps. I said in my 1st reply that it may be a huge current being drawn. That’s wrong, it will only be mA’s. Not enough to blow the fuses but enough to drain the battery over several hours.

 

[suffolkspark]

Does that vehicle have a smart charge system? Some have that where electronics decide to charge a battety at a higher voltagge for a period after starting etc, could be faulty and confused of what to put out, on some fords this curcuitry was seperate from the alternator, i know this isnt a ford but something to google

 

[Rodders099]

Suffolkpark is quite correct.
And if after checking your battery, alternator and eliminating any earth fault.
It would more than likely be a problem associated with the vehicles electronic brain.

 

[Squid]

Check the earth cable from engine to chassis.