Battery icon on dashboard doesnt light up

Tiny
R.PERK
  • MEMBER
  • 2000 FORD TAURUS
  • 150,000 MILES
Battery icon on dashboard doesnt light up. Could this stop alternator from charging battery?
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Thursday, February 28th, 2013 AT 9:56 PM

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Tiny
CARADIODOC
  • EXPERT
Absolutely. That is the turn-on circuit for the voltage regulator on the back of the generator. Look for a two-wire connector near the generator and check those terminals for corrosion. Also look at the three-wire connector right on the back of the generator.
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Thursday, February 28th, 2013 AT 10:09 PM
Tiny
R.PERK
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Thank you for your advice. Sorry it took me so long to get back to you. But anyway, I looked for 2 wires I can't find them. Let me explain what i'm going through. Someone changed the engine, broke 7 wires, 4 on harness plug connecting to the plug going inside. 3 were ground wires to firewall. Battery won't charge. Changed alternator 4 times. All checked out ok. The battery icon does'nt light up. Now I need to changed fuel pump to get it started again. Do you have any more ideas why it won't charge? Desperate for help.
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Monday, March 4th, 2013 AT 10:45 PM
Tiny
CARADIODOC
  • EXPERT
Here's a photo from my web site. The back of your generator is going to look different but it uses the same voltage regulator as shown here so the connector will be the same. Your wire colors might be different but the locations within the connector are what is important.

In this one, the green wire with the red stripe comes from the "battery" light on the dash. 12 volts is on the other side of that light when the ignition switch is turned on. Without getting "wrapped around the axle" with electrical theory, if you unplug that connector, and turn on the ignition switch, you must find 12 volts on that terminal if you're using a digital voltmeter. If you're using a test light, expect its bulb to glow dimly, not full brightness. If you DO find voltage there, use a clip lead or piece of wire to ground that terminal to the engine or generator's case. That will turn the "battery" light on full brightness. If that voltage is missing, there is a break in that wire. To verify if that is all that's wrong with the charging system, I can tell you how to fashion a temporary bulb circuit to trick it into working.

If you do have 12 volts there, measure it again by back-probing through the rubber seal when it is reconnected. You'll have to do that with a digital voltmeter, not a test light. You should have around 2 volts. If you do, the dash light should be on. If it is not, the bulb is burned out. That would not be the issue now because there is also a resistor on the gauge cluster to get things started if the bulb burns out.

If you find around 2 volts, that turn-on circuit is working. That "wakes up" the voltage regulator and turns it on. The other side of that circuit needs 12 volts and that comes in on the yellow wire. That will be there all the time, even when the ignition switch is off. Back-probe that wire and check for it. If it is missing, look for a blown 15 amp fuse or a fuse link wire that is burned open. I only know a '94 Explorer uses a fuse and a '93 Tempo uses a fuse link wire.

If both of those voltages are correct, the only thing left is a problem in the voltage regulator or brushes, or a problem in the output circuit. I doubt the problem is in the regulator since you've tried four of them. Still, see that sad red and blue arrows? The red one is pointing to the arrow that is pointing to the screw the blue arrow is pointing too. You'll need the engine running for this test. Use a piece of wire to ground that screw. That will bypass the regulator. If the headlights get bright, battery voltage goes up, and you hear the generator straining, that proves the regulator is defective and everything else is okay.

A different test is to measure the voltage on that last white / black wire. When the generator is working you will find half of battery voltage on that wire, around 7 volts.

If all of that seems to be working, there's a problem in the output circuit, either with a blown very large fuse in the under-hood fuse box or with a burned open fuse link wire. There's two things that will identify that. First, with the engine running, the voltage on the large output stud will be significantly higher than the battery voltage, as in 15 - 18 volts. Second, with the engine off, there will be 0 volts on that output terminal. The voltage on that terminal should be exactly the same as the battery voltage at all times.
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Tuesday, March 5th, 2013 AT 2:36 AM

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