Charging problem - DB (Case) 995

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staffstractorboy
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Joined: Sat Jan 05, 2013 6:21 pm
Location: Staffordshire

Charging problem - DB (Case) 995

Post by staffstractorboy » Thu May 22, 2014 5:33 pm

My alternator is no longer charging the battery. The warning light came on for a long period when the tractor was running and eventually went off. It now won't come on when the ignition is switched on. A multi-meter test shows that when the engine's running the battery voltage is only 12 - 13v. The ignition warning light bulb is OK. I've disconnected the 3 pin plug from the back of the alternator and on the two large terminals I get a 12v reading when I earth it through the multimeter. However when I've earthed the third and smaller lead which I understand carries the "exciter" current to the alternator and then switch on the ignition, the warning light doesn't come on as it should. Does this mean there is a problem with the charge warning light circuit and how can I fix it? Grateful for any advice.

JamesF
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Location: South Yorkshire

RE: Charging problem - DB (Case) 995

Post by JamesF » Thu May 22, 2014 6:26 pm

Usually when strange things start happening with the charge light, ie light on continuous, no light at all and bulb ok, dim light on getting brighter with increased engine revs etc it's something to do with the internals of the alternator. Most probably a problem with a phase or the rectifier. Bad alternators can cause fires particularly if it is discharging the battery when not running, they get quite hot!

My advice would be replace the alternator but don't over pay for a new one. I'm not suggesting going straight for a cheap nasty copy but shop around a little, 65 to 70 pounds at most will buy a decent quality unit.

John_Allen
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Location: Cumbria UK

RE: Charging problem - DB (Case) 995

Post by John_Allen » Thu May 22, 2014 6:51 pm

If you are shorting out the end of the warning light lead to earth, the warning light should light up. Does the oil pressure light come on as it should? If it doesn't I'd suggest you look to see if there's power at the ignition switch, if it does, there will probably be a bad connection or broken wire between the bullet connector (or whatever) that serves the ignition warning lamp and the connector at the alternator end of the circuit. There won't be many connections on an early 995, though a Q-cabbed one is a little more advanced (and awkward) to check!

I suspect that, if the alternator isn't getting the excitation from the ignition switch (and light), a replacement alternator won't cure the problem, so make sure you get the circuit sorted before buying a new alternator. As you say, the warning light should come on when the alternator end of the circuit is taken to earth.

Hopefully, you have the Operator's instruction book - certainly the early ones have a wiring diagram that should help work out what connectors are between one end of the circuit and the other.

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bedwards1966
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RE: Charging problem - DB (Case) 995

Post by bedwards1966 » Thu May 22, 2014 11:12 pm

As John Allen has said, begin by looking at the warning light circuit. The lamp must illuminate when the wire is earthed for the alternator to excite and begin charging.
When you get that sorted it's always worthwhile to check the alternator is well earthed. If it still doesn't work then the alternator will need attention, you can replace the internals with a little time and a soldering iron (google LUCAS ACR alternator repairs, there'll be information out there) or you can replace with a new one.

SteveCollett
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Location: Suffolk

RE: Charging problem - DB (Case) 995

Post by SteveCollett » Fri May 23, 2014 9:53 am

if you buy a non genuine one , be very wary that it fits correctly. make sure you washer it so sits correctly and the pulley is dead in line. Otherwise 2 things will happen. You may wreck the belt if it is out of line, perhaps more importantly, if the holes on the alternator do not fit snug to the brackets, you will break the casting as you tighten the bolts. Make sure you washer it

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staffstractorboy
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Location: Staffordshire

RE: Charging problem - DB (Case) 995

Post by staffstractorboy » Fri May 23, 2014 3:33 pm

Thanks for all the advice. I re-ran the test of the on the smaller lead which carries the "exciter" current to the alternator and this time the "Charging" warning light came on as it should. I suspect that now means that the alternator needs to be replaced.

JamesF
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Joined: Tue Mar 14, 2006 8:49 pm
Location: South Yorkshire

RE: Charging problem - DB (Case) 995

Post by JamesF » Fri May 23, 2014 10:13 pm

Nine times out of ten it's the alternator. The wiring usually doesn't suddenly give trouble unless it's been damaged by an animal chewing it or when another repair has been carried out. Usually with a wiring harness fault you get intermittent problems when the circuit makes and breaks with movement and vibration.

When it comes to using washers to space the alternator in its bracket most alternators come with a small piece of tube which acts as a distance piece. These can however be tight in the alternator body and damage can still be caused.

Guest

RE: Charging problem - DB (Case) 995

Post by Guest » Fri May 23, 2014 10:40 pm

Put a meter on the alternator to determine if there is output, it should be just over 14V on the charge side, seems to me that the rectifying diodes have gone not just the charge side, if that was the case then the ignition light would be on all the time. Another important point is to put the existing pulley from the old unit onto the new one if you have to get a new or used alternator.

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