Mechanics

CAR WONT KEEP A CHARGE

1988 Chrysler 5th Avenue • V8 Automatic •

I have a 1988 Chrysler 5th avenue. New battery and new alternator. Car still cant keep a charge. When I install the alternator I I feel like im missing a wired but can not find it. I have a total of 4 wire connect to the alternator. But there is a screw that doe not have a wire. What should I do?
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Joe34444
November 23, 2010.




There are only three wires, the two small field wires are interchangeable, and the fat output wire bolted that's on. Chrysler charging systems have always been very reliable and easy to troubleshoot. Measure the voltage on the green wire while the engine is running. You should find less than battery voltage, but not 0 volts. Grounding that green wire will make it charge wide open. Lights will get bright and battery voltage will go up to over 15.0 volts. Don't do that for very long and don't increase engine speed too much to prevent damaging the Engine Computer and any light bulbs that are turned on. Holler back and let me know if that worked.

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Caradiodoc
Nov 23, 2010.
Had to fix typographical errors!

There are only three wires, the two small field wires are interchangeable, and the fat output wire that's bolted on. Chrysler charging systems have always been very reliable and easy to troubleshoot. Measure the voltage on the green wire while the engine is running. You should find less than battery voltage, but not 0 volts. Grounding that green wire will make it charge wide open. Lights will get bright and battery voltage will go up to over 15.0 volts. Don't do that for very long and don't increase engine speed too much to prevent damaging the Engine Computer and any light bulbs that are turned on. Holler back and let me know if that worked.

If you find 0 volts on the green wire, check to be sure there's 12 volts on the blue wire. If so, the brushes are open. They are bolted to the back case of the alternator. The blue and green wires are clipped or bolted to them. Those brushes can be replaced very easily without any other disassembly. Some can even be replaced without removing the alternator from the engine. The pair costs three bucks.

If you find full battery voltage on both the blue and green wires, there is either a break in the green wire or the voltage regulator is defective. He lives on the passenger side of the firewall and also has a blue and green wire in the triangular plug. Unplug that connector and use a jumper wire to ground the pin for the green wire while the engine is running. If that makes it charge wide open, replace the regulator. It must be bolted solidly to the firewall to work because that's how it gets its ground. Be sure there's 12 volts on that blue wire too.

Every dark blue wire under the hood has 12 volts when the ignition switch is turned on but for people researching other vehicles, particularly some early '90s trucks, they used dark red wires instead of dark blue. The dark green wire is still the field control wire going from the alternator field terminal to the voltage regulator.

If you find somewhere between 4 and 11 volts on the green wire, (it must be plugged in on both the alternator and the regulator, that part of the circuit is working correctly. If output is low, suspect a shorted diode in the output circuit. That will show up as excessively high ripple on a load tester capable of measuring that. During a full-field load test, one shorted diode will cause the alternator to only be able to deliver very near one third of its rated value. The smallest alternator available for cars with air conditioning puts out 55 amps so under full load with a bad diode, you would get around 20 amps max.

Caradiodoc

Caradiodoc
Nov 23, 2010.
I understand what you are saying. I need detail help on how to get too my voltage regulator? And what tool do I need to test the voltage

Tiny
Joe34444
Nov 23, 2010.
Use an inexpensive digital voltmeter. Sears, Walmart, and Radio Shack have them. Don't waste your money on the expensive ones. They don't work any better, they just do a lot more functions that you don't need. If you have a Harbor Freight Tools store nearby, they have one for around $7.99 that goes on sale quite often for $2.99. Just be sure the test leads are plugged in tightly so they make good contact. Set it to the 20 volt DC scale for the best accuracy. That means it can read anything from minus 20 volts, (hooked up backwards), to plus 20 volts. Higher scales will work too but you will lose one place after the decimal point of accuracy. You need to read to the tenth of a volt.

Put either lead, typically the black one, on the battery negative post or a clean, paint-free point on the engine block, and touch the red lead to the point you want to measure, in this case, the green wire on the back of the alternator or in the plug for the regulator.

The voltage regulator is rectangular, about 3" by 4", an inch thick, and has a black triangular plug with room for three wires but it only has two in it. The blue wire is in the middle and the green wire is in one side. There is a metal band that you have to squeeze on the sides to release the plug. That regulator is usually silver but I've seen black and gold ones. Two bolts hold it to the firewall. They are not straight across from each other and are not in a symmetrical pattern.

You might have an orange or red box on the firewall that almost fits that description but it is smaller and has different wires and plug. That has nothing to do with the charging system.

You can use the voltmeter to measure battery voltage too and to make a quick test on the charging system. A fully charged battery will measure very near 12.6 volts. A good but discharged battery will read around 12.0 volts. A defective battery with one shorted cell will have about 11.0 volts. When the engine is running, if the charging system is working properly, you will find between 13.75 and 14.75 volts. It might creep up a little from time to time, especially in cold weather, but anything over 15.0 volts is undesirable. The regulator has temperature compensation built in. That's because recharging the battery after starting the engine is a chemical process and chemical reactions slow down in colder temperatures. By bumping up the charging voltage a little in cold weather, it helps to fully recharge the battery more efficiently.

Caradiodoc

Caradiodoc
Nov 23, 2010.

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