Alternator Not Charging

[PatHB62]

Greetings all!! Newbie here. I have a '90 Ranger XLT 2.9/A4LD - it's been run half to death over the years and I've picked it up within the last year. Nursing it along until my financial situation inproves. My voltage gauge started reading low yesterday evening. I pulled the alternator apart and discovered/replaced a broken brush - snapped in half... I've put a newer charged battery in it and still showing low voltage. Wondering what else I can check - all the wiring "looks" good. The truck starts fine - wondering if something in the starter solenoid could be bad. All the fuses in the underhood power box look good... Scratching my head - gotta be to work by 10 tonight or find someone to replace me.. No voltage testing equipment at all - just looking at obvious stuff. Thanks for any help!!!

 

[PatHB62]

Alternator is less than a year old as well - may just have to take it back to the folks that installed it....

 

[RonD]

Is it the stock alternator?
One "nut" terminal and one connector with 2 wires and a short jumper(to and from alternator)

First check connector, those wires get frayed and only 1 or 2 threads remain.
These wires "turn on" the alternator.

With key off test battery voltage, should be about 12.7v

With engine at idle test voltage at the Nut terminal on the alt., if voltage is the same as the above voltage then alternator is not "on", if its less voltage then alternator is drawing power from the battery.
If Voltage is only slightly higher(13.1v) than battery voltage then alternator is working but voltage regulator is not, it is either not "on" or is set at minimum, so not detecting a need for higher power.

 

[Twister]

Is it the stock alternator?
One "nut" terminal and one connector with 2 wires and a short jumper(to and from alternator)

First check connector, those wires get frayed and only 1 or 2 threads remain.
These wires "turn on" the alternator.

With key off test battery voltage, should be about 12.7v

With engine at idle test voltage at the Nut terminal on the alt., if voltage is the same as the above voltage then alternator is not "on", if its less voltage then alternator is drawing power from the battery.
If Voltage is only slightly higher(13.1v) than battery voltage then alternator is working but voltage regulator is not, it is either not "on" or is set at minimum, so not detecting a need for higher power.

His would be a 2g alt so no "nut" on the back only the rectangle plug and the "D" plug.

You are going to need to get a simple voltage tester. Trying yo diagnose voltages without one is hopeless. They are cheap, you can get one for under $20.

Sent from my SPH-L900 using Tapatalk 2

 

[PatHB62]

Yeah need to get a meter eventually - I was able to borrow several good batteries from my roommate and have charged them - it will last long enough to get it to the shop that installed it - hopefully I haven't screwed up the warranty by fooling with it myself... Thanks all!!!

 

[dave2575]

Sounds to me like there might be something wrong with the alt. You should have a local auto parts store check it, allot of parts stores will check em for free. If you got a new batt make sure that it is FULLY charged before trying to fix anything else. Remember alternators DO NOT charge the battery, they only maintain the battery's charge. In other words, if your batt is low and only has 11.5v while running, then the alt will only maintain and or keep that 11.5v charge. Old school cars had Generators that would "actually" charge the batt.

Dang it! You replied while I was typing and basically covered everything I said above. lol

 

[alwaysFlOoReD]

Remember alternators DO NOT charge the battery, they only maintain the battery's charge. In other words, if your batt is low and only has 11.5v while running, then the alt will only maintain and or keep that 11.5v charge.

So how come when I have a dead battery....not even clicking at the solenoid, and get a jump, the battery seems to charge and will start fine after a long drive?

Richard

 

[Surrey]

Remember alternators DO NOT charge the battery

Thats a god damn lie. Alternators DO charge the battery, as long as they are working properly. Your battery only needs 12.something volts, and the alternator puts out over 14 if its working right.

 

[RonD]

Yes alternators do charge a battery, but some confusion can exist about that.
When a car battery is drained below 11v it can suffer damage, they are not made for that kind of discharge, deep cycle batteries are.
So if someone drains their car battery down too low it may not recharge or may not hold a charge.

To maintain any battery you need to supply it with at least 1 volt above it's current voltage, to charge it 1.1-1.5v are needed.
If a battery is 12.7v with engine off, then alternator should read 13.7v or higher when engine is running, it can go as high as 14.9v if car was hard to start and had a longer drain, but never higher than 15v, as that will also damage a battery.

Generally speaking your 12v system runs at about 13.8 volts when engine is running.
This maintains the battery's 12.7v charge and runs the other electrical devices.

 

[kimcrwbr1]

The alternator is not designed to charge a dead battery but it will and is real hard on the alternator and regulator. It is allways best to fully charge the battery with a slow charge usually 12.6-12.8 volts. Then you do a load and no/load test to determine if it is charging correct. There are two wires going to the alternator the large one is full time hot battery voltage and the other is key on hot. If the wiring is correct start it up and do both tests load and no/load. A good way to check the battery is fully charge it and measure the battery voltage let it sit for 24 hours disconnected and if it loses voltage the battery is bad. +1 on you have to have a volt meter to confirm it is working properly any one of the three components will toast the other two real fast battery, alternator, voltage regulator all work together. I will give you the link get a cheap volt meter read through it a few times and then do the diagnostic.

 

[kimcrwbr1]

http://www.therangerstation.com/tech_library/chargingsystem.htm