1999 Plymouth Voyager Battery Light on

Tiny
JTPARKS
  • MEMBER
  • 1999 PLYMOUTH VOYAGER
Electrical problem
1999 Plymouth Voyager 6 cyl Front Wheel Drive Automatic

I have a 99 Plymouth Grand Voyager and the Battery light is staying on, the Alt is good, but it seems the battery will not hold a charge, had it tested and it is good. Could I have a relay staying open? And if so, how can I test? Or could it be something else.

Thanks
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Wednesday, April 14th, 2010 AT 6:50 AM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Start by measuring the voltages on the two small wires on the back of the alternator while the engine is running. One must have full battery voltage. The other wire should have less, but not 0 volts. Those voltages will tell us where to go next.

Caradiodoc
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Wednesday, April 14th, 2010 AT 11:31 AM
Tiny
JTPARKS
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The 2 wires are behind the Alt, and they said they could not get to them. I had the Alt. Tested and was told that it was on its last leg, not all the way gone but, almost there, so put a new one in. Charged the battery, on low all night, then started van. Stared fine, then a couple of seconds later, battery light came on again. Just frustrated.

Thom
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Thursday, April 15th, 2010 AT 6:06 AM
Tiny
CARADIODOC
  • EXPERT
I take strong issue with "on its last leg". It is very common for these alternators to be intermittent. A worn tire can be on its last leg. A rusty muffler can be on its last leg. The parts inside an alternator, with the exception of the brush assembly, are good or bad, no in between. Only the brush assembly, when worn, will cause the unit to start working again at times. The test is to measure the voltages on the two small wires while the engine is running. I've done it numerous times, but it is easier from underneath. Clip leads can also be run up to a place that's easy to reach from the top.

If one diode fails in the alternator, you will lose two thirds of its capacity, but that alone will not turn on the battery light and will not cause a battery to die while driving. Some testing equipment will indicate a bad diode, but it won't cause your symptoms.

The issue of access is irrelevent anyhow since the alternator has been replaced. That eliminates one possibility and leaves two suspect circuits. The feed circuit is the least likely to cause a problem because the same circuit feeds the injectors, coil(s), and fuel pump or pump relay. Since the engine runs, you know that circuit is working. Only a short piece of wire or a corroded splice are in the circuit to the alternator.

The other circuit is the dark green wire from the alternator field to the voltage regulator in the Engine Computer. You can measure that voltage in connector 1, pin 4. It's a very thin 16 gauge wire, (dark green). There are three possibilities. 0 volts indicates a break in that wire, typically a corroded pin in a connector. Well, ... Typically the worn brushes in the alternator, but it has been replaced already. Full battery voltage indicates a defective regulator, (Engine Computer), or a loose connection in that connector which isn't very likely. If the system is working properly, there will be typically somewhere between 4 and 11 volts on that wire. In that case, the alternator's output is not getting back to the battery. Here again, measuring on the large wire bolted to the back of the alternator will provide the clue.

Caradiodoc
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Thursday, April 15th, 2010 AT 1:12 PM
Tiny
JTPARKS
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Thanks for the info, I will give this a try. Recharging battery now.
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Thursday, April 15th, 2010 AT 2:14 PM
Tiny
2CARPROS LINSEY
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Hi jtparks, thank you for using 2CarPros. Com. We appreciate your donation and look forward to helping you in the future.
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Monday, April 19th, 2010 AT 3:13 PM

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