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Discussion Starter · #1 ·
It's a 1990 cabrio digifant II. The battery light used to light up and if you bring the rpm a bit up it would go away. However, now it doesn't light up and i have to rev to about 3500 rpm in order to see the battery charging on the volt gauge. I read that the faulty led light can cause that so i switched led around in the cluster. That wasn't the problem.
Anyone else had similar problem? Any help is appreciated.
Thanks in advance.
 

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'81 Trek 614, '95 Ranger
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Re: 90 cab battery light won't light up. (Groove_D)

Find the blue wire on the small post on the back of the alternator.
Disconnect it to be completely safe, or leave it connected and be careful.

Key on, engine off, ground the blue wire, the battery indicator should light, do not start the engine while that alternator post is grounded.

If the battery indicator lights with the blue wire grounded, the exciter circuit is good, shop for an alternator.

If the battery indicator does NOT light with the blue wire grounded, there's an open in the exciter circuit, the alternator cannot work properly and dependably without a properly functioning exciter.
Common causes are a corroded blue wire or inline connector in the blue wire, usually under the battery; an open in the instrument cluster is also possible.

Are all other functions of the instrument cluster fully functional?
 

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Discussion Starter · #3 ·
Re: 90 cab battery light won't light up. (tolusina)

Thanks for the quality post. My buddy told me similar way to test it out. He said to take a low impedance test light and give power or ground to the blue wire. He said he doesn't remember power or ground. Said to try both.
Yea pretty much everything functions. I will do the test and update the thread.
 

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Re: 90 cab battery light won't light up. (Groove_D)

You can indeed use a test light as a substitute exciter, high (LED type) or low (bulb type) impedance doesn't matter.

Connect the clip lead to battery positive, the probe to Terminal 61 (post on the alternator where the blue wire connects).
Key off or on, engine off, the test light should light. Start the engine and rev it a bit once, the test light should go out and the alternator, if good, should start charging. Test for charging voltage with a voltmeter.
Also, once the alternator is excited and charging, it should continue to charge even after the test light has been disconnected until the next engine start cycle when it needs to be re-excited.
 

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Discussion Starter · #5 ·
Re: 90 cab battery light won't light up. (Groove_D)

Just did a quick check. Not at home right now so didn't have my ohmmeter. All i had were the litle aligator clips jumper wires.
I tried grounding the little wire at the alternator and either i couldn't get a good ground or the wire is broken somewhere till the connector besides the battery + terminal. When i disconnect the plug on the blue wire near the battery + terminal and give the wire a ground, battery light lights up. I will get my multimeter and will test the wire for continuity plus i will get a longer jumper wires.
Will keep this thread updated.
 

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Re: 90 cab battery light won't light up. (sehaare)

Quote, originally posted by sehaare »
... it's the root of most charging problems. Steve

No way, Steve. My ex was, "the root of most charging problems."
 
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