Flat Batteries - charging issue?

1998 KZJ95 Chris

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I am in cyprus
Jan 23, 2018
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Having an issue with my KZJ95.

Dual battery set up, not enough juice to start after work today but jumped with 12v jump pack on the driver side battery. I had been driving around all day on and off and thought id just not left it long enough running to recover, but it didnt start again once id driven for 30 mins after work. No charge light on the dash unless I switch the lights, AC and radio all on at once, then the dash lights up like a Christmas tree.

At idle I get 11.4 volts (measured at the battery terminals on both batteries) This doesn't change when revs are increased, but drops to around 10v when I switch the lights on. I am leaning towards a knackered alternator, but I haven't checked the output, can anyone give me a walk-through on where to stick the test leads please? I'd rather check and confirm before shelling out on a new alternator.

Thanks


Checked 100A fuse and looks ok
 

Towpack

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Check all the wiring connection first. Battery posts, chassis earths and the alternator connections, including the multi plug connector. An alternator needs power itself to work so a bad connection here will affect output. All the readings you have given are low. Typically 13.5 to 15v max are acceptable charge voltages from a fast idle upwards. The alternator should be able to handle the load of lights, air on, radio etc and still charge the battery when the engine is revved. Check the voltage between earth and battery post compared to that between earth and the main output terminal on the alternator for voltage drop. It should be negligible, maybe 0.1-0.2v no more.
If all these check out then the next step is remove and strip the alternator to check brushes/sliprings (if it has them) and the diodes of the rectifier along with continuity of the windings.
 
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StarCruiser

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As above. You should be getting 14.4v at the battery. Any closer to 15v will start to cook the battery but as mentioned the output could be a little higher, 14.6 perhaps. It’s sounding like you may have a fault on the regulator. You could also have stuck brushes or a blown diode. Talk to Robson and Francis for replacement parts or a replacement alternator but check the simple things first. Have a voltmeter across the battery and wiggle the plug on the back of the alternator to check if the voltage rises at all. Check the ‘charge’ fuse or whatever it is called on your truck.
 

clivehorridge

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I’d start with the alternator plug at the back first, they seem notorious for having bad connections after 20 years or so.

It's a fiddle to remove, but we'll worth the effort before going around all the earth straps and other connections.

Mine delivers 14.2V on start up and only drops to 14 or 13.9 on idle, even under load.
 
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Bob

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Likewise I get 14.1v from the alternator.

As others have said, check cables and connections. Otherwise the dual batter set-up has one flaw in that the second battery will drag the cranking (drivers) battery down too if it's on the way out.
 

StarCruiser

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Aren’t these batteries permanently connected in parallel Bob? Unlike the 80s, set to give 12v? If so both would be used as one for cranking, charging and accessories. Or have I got this wrong? Either way, charging voltage is way down.

Any luck yet @1998 KZJ95 Chris ?
 

Bob

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You could well be right! I presumed it was the same as the 80 set up.. my truck only ever had one battery, as did all 90s sold here.

(Still has the idle-up switch and it works, so the 'winter pack' idea may not be what it seemed)
 
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StarCruiser

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I use mine for warm ups and jump starting. It’s the old fashioned cable pull one (where the knob usually pulls off in your hand). I would actually consider an electrically operated mod to use the idle up for the AC, that the 80 has, for winching and to replace the pull cable.
 

Towpack

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I use mine for warm ups and jump starting. It’s the old fashioned cable pull one (where the knob usually pulls off in your hand). I would actually consider an electrically operated mod to use the idle up for the AC, that the 80 has, for winching and to replace the pull cable.
I prefer the cable pull type so I can hang my handbag on it:thumbup:
 
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Jack VZJ90

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build 1998, 1st alternator ?
Mine was build 1997, 350.000 km, and i recently installed a new alternator.
I noticed with lights and fan on with lowering engine speed, the fan slowed down and the lights became less bright.
You can rebuild you alternator with new power regulator, but if it came original with your car, you better of buying a new one.
Good power and less noise :grinning:
Easy to install by yourself .....
 
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Trevor

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Have you checked the condition (load test) of the batteries independently i.e. when they are not connected in parallel. Often the battery closest to the starter fails first and will pull the second battery down with it giving the symptoms you describe.
 
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