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Recently, the battery light on the dash remained lit. After a few hours parked, the battery would be drained. I was told that the alternator needed replacing. A rebuilt Lucas alternator was installed. The battery light now goes out as it should upon starting. However, the battery drained if the car wasn't driven within 24-36 hours. A new battery was installed. The battery still drains after 24-36 hours. The alternator charges at 14 volts. If disconnected, the battery holds charge after 2 days. How can I test if the alternator has a short or not?

Cheers!
 

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Testing Alternator and Regulator

Start the engine and run it at about 3000 rpm with all electrical accessories turned off. Set the voltmeter to the DCV scale and measure the voltage between the positive and negative terminals of the battery. Make sure that the tester is connected to clean areas of the terminals. A reading between 13.5 to 14.5 volts indicates a correctly operating system. A reading higher than 14.5 volts most likely indicates a faulty voltage regulator.

A reading below 13.5 volts means that the battery is not being adequately charged because either the regulator or the alternator is faulty. To determine which, keep the car running at about 3000 rpm and turn on all electrical accessories, then check voltage across the battery. A reading that is the same as the first most likely indicates a faulty regulator. A reading that is lower most likely indicates a faulty alternator.

Testing Current Drain


If tests show that the alternator and regulator are operating correctly, but the battery still continually runs down, there may be a short in the electrical system causing a continuous current drain.

To test for current drain, turn off the ignition switch, the radio, and all lights. Disconnect the clock, if so equipped, by removing its fuse. Turn on the switches for the heated rear window and, if applicable, the air conditioning; this will determine if the load reduction relay is faulty. Disconnect the negative (-) cable from the battery and connect a test light between the cable and the negative post. If the test light comes on, some electrical accessory or a short in the electrical system is draining current from the battery. Isolate the faulty circuit by removing and replacing the fuses one at a time. When the test light goes out, the circuit with the short is located. If no fault is found in this way, a fault may exist in the components without fuses, such as the alternator, the starter motor, the ignition system, and the instrument cluster. Disconnect the items one at a time until the test light goes out.

Low level current drain may not be detectable with a test light. If the light does not come on, but a current drain is still suspected, repeat the test using an ammeter set to the 0 to 200 mA range.
 

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Discussion Starter #3
Thanks.
It appears to be the voltage regulator.
Cheers!!
 

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I don't want to steal this thread, but I too have a similar issue-

I have had a constant lit battery light on the dash now for a couple of days. Based upon idle speed and what is on, it will be really dim or bright as heck. Today, based upon this post, I started trouble shooting the issue. I suspect the alternator, but wanted to walk through the great instructions posted here.

Rover not started- Battery reads 13.06 volts
Rover started at idle- Battery reads 14.01 volts
Rover started and RPM at 3000, no accessories on- Battery reads 14.25 volts
Rover started and RPM at 3000, heater fan on full blast, lights on high beam and auxiliary lights on- Battery reads 13.35 volts

Conclusion based upon findings- Battery is good, Voltage Regulator functioning correctly, Alternator on the way out.

Anything that I am missing?

Thanks for the help up front.
Dustin
 

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Sounds to me like your alternator is bad.

Have you considered a VW Bosch alternator swap?
I pioneered it back in '04.

http://www.3dzubehor.com/Rover/Boschalternator.html

vwzach182 recommends using this belt Napa belt XL #25-9290.

My alternator tensioner was placed on a different bolt at the water pump.
That is why I recommended that belt that I did in my write up.
 

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I did look at that write up. Looks very interesting and fun, but based upon time and the fact that I have been forced to turn this Rover back into a daily driver, I spent the afternoon yesterday locating a re-manufactured unit here locally and picked it up today. Obviously not the most cost efficient venture I can tell you that.

Just got home from work, gonna clean up, say hi to the kids and head to the shop.

DM
 
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