Charging Issues - New Batt & Alternator

'97 Ranger 4.0L V6 Auto

Battery was 5 years old and quit about a month ago, replaced it, no problem. A few weeks later battery light starts coming on, only getting 11.8V from the alternator, so I replaced it with a Reman'd alternator (had Advanced Auto bench Test the old and the new before I replaced). Fully charged battery, start truck, let run 20 min, no charging, voltage @ battery drops slowly as truck runs?

Any suggestions? I have continuity between Alternator post and Battery, continuity between grounds. I checked Alternator Fuse, continuity present.

Any one know of what this could be? I was wondering Starter Solenoid on fender cause the alternator lead returns to there and then to the battery? IDK

Thanks in advance

Seems good to me..

7upedition said:

'97 Ranger 4.0L V6 Auto

Battery was 5 years old and quit about a month ago, replaced it, no problem. A few weeks later battery light starts coming on, only getting 11.8V from the alternator, so I replaced it with a Reman'd alternator (had Advanced Auto bench Test the old and the new before I replaced). Fully charged battery, start truck, let run 20 min, no charging, voltage @ battery drops slowly as truck runs?

Any suggestions? I have continuity between Alternator post and Battery, continuity between grounds. I checked Alternator Fuse, continuity present.

Any one know of what this could be? I was wondering Starter Solenoid on fender cause the alternator lead returns to there and then to the battery? IDK

Thanks in advance

Click to expand...

" Fully charged battery, start truck, let run 20 min, no charging, voltage @ battery drops slowly as truck runs?"

Seems like that is what a good charging system is supposed to do..
SO.. is the only problem you are having now.. in your head?
OR is something BAD happening that you havn't bothered to report here?

Do this... when the system starts lowering the output .. turn the headlights on and put heater fan on high.. then look at what the system is putting out. The voltage regulator is SUPPOSED to keep the battery charged.. if it IS DOING that then you are Ok.
Big JIm

Problem is that the battery is not recharging. Voltage will start at 12.5 volts and drop .1 volt down to 11. When I drive the truck the alternator is not recharging the battery causing the truck to cut out.

I have a known good battery and alternator, but the charge isn't making it from the alternator to the battery.

Thanks

Take the battery cables off the new battery and make sure they are cleaned good. Your description is of a BAD alternator... Take it back and have it tested again.. It prolly has failed. Also there is a chance that you have left a wire off somewhere that you took off..

Big JIm

Have you checked the fusible link in the alternator harness that goes to the starter solenoid? Check it for continuity. besides that I can't see any other problem besides the possibility of having a bad alternator from Advanced Auto.

On these Rangers, does the battery need to be disconnected before the alternator is swapped out? I have always done it when I worked on my older GM and Chrysler's but never gave much thought on my Ranger, I've always just did it out of habit.

If not, one needs to be VERY careful! I always disconnect the negative cable on any vehicle... I don't like sparks..
Side note: A friend just put a battery in backwards in his daughters Nissan.. The thing has been sitting there for 4 days now. Something besides the 100 amp fuse has blown and he can't find it.. I guess I'll have to pay him a visit to see if I can find the burnt item.
Big JIm

Guys, Thanks for the advice. I hit all the basics. It is a known good alternator, it was bench tested, terminals and cable cable clamps are new and clean. Also the battery was disconnected when installing the alternator (i always do this out of habit).

Trex, I haven't chased down the fusable links yet, but don't suspect them as all the accessories work and the vehicle starts.

I did some troubleshooting and suspect I have a short somewhere. When the key is off, and the neg cable is disconnected I have a voltage of 12v between the battery terminal and the neg cable, indicating a short. I guess I have a bit of digging around to do to find the source... any suggestions where to start the search?

Thanks

7upedition said:

Guys, Thanks for the advice. I hit all the basics. It is a known good alternator, it was bench tested, terminals and cable cable clamps are new and clean. Also the battery was disconnected when installing the alternator (i always do this out of habit).

Trex, I haven't chased down the fusable links yet, but don't suspect them as all the accessories work and the vehicle starts.

I did some troubleshooting and suspect I have a short somewhere. When the key is off, and the neg cable is disconnected I have a voltage of 12v between the battery terminal and the neg cable, indicating a short. I guess I have a bit of digging around to do to find the source... any suggestions where to start the search?

Thanks

Click to expand...

I'd start with the main wires going to the starter. With both cables disconnected check for continuity between the negative cable and the positive terminals in the alternator and viceversa....

Happy hunting!

-Trex

The light on the dash is on? and won't go away?

The light bulb is a very key item on a 3 wire alternator system. That bulb is inline with a wire that excites the alternator. As soon as the alternator starts charging it is no longer a ground and the light bulb I guess breaks the circuit so to speak. Therefore I would make sure everything in line with that wire is good to go. Check the plug on the driver side fender well. I accidently un-plugged this when changing an alternator out and ran into the same issue..

Update

Guys, Here's an update... it's 15*F in NY and Snowing... this has been a blast working outside. Anyways:

-Battery is Good
-Alternator is Good
-Continuity between starter/battery & vice versa, checks out ok.
-Checked every fuse in the truck, checks out ok, couldn't find a short that goes through the fuse panel (VOM between Neg Term & Neg Cable still 12V)
- Jumped the alternator directly from the output post to the + terminal, and the alternator casing to the - terminal and still no charging, that rules out bad ground or return wires.

I suspect theres a bad wire in either the 3 wire or single wire plugs that go into the alternator. Does anyone have a diagram of these wires and where they go?
Tonight, in the dark and snow and 10* weather I'll be in the driveway with a flashlight pulling the sheaths and inspecting the wires and connections.

Thanks

AaronC said:

The light on the dash is on? and won't go away?

The light bulb is a very key item on a 3 wire alternator system. That bulb is inline with a wire that excites the alternator. As soon as the alternator starts charging it is no longer a ground and the light bulb I guess breaks the circuit so to speak. Therefore I would make sure everything in line with that wire is good to go. Check the plug on the driver side fender well. I accidently un-plugged this when changing an alternator out and ran into the same issue..

Click to expand...

Aaron, The light and VOM is functioning properly, the issue is getting the alternator to charge the battery (or getting the alternator the signal to recharge the battery). On the 3 wire, I think the one wire is a jumper to the single wire, and one goes to the battery light/dash VOM, and the other is for ?

dont mean to bump this.. having the same problem with my truck..

Have the same problem battery light on/VM reading low. Rebuilt(new) alternator and battery checks good(load test)
Alternator B+ terminal 12V with engine running. Going to replace 3 wire and single wire connectors.

Read this all the way through a couple times print it out and grab your volt ohm meter and attack to check for shorts with the key off disconnect the posative battery terminal and check between it and ground there are a couple things that may be using the battery full time the computer and the radio memory/clock and normally read high resistance not a direct short. If it was a direct short something would be smoking or getting real hot. In troubleshooting the alternator/regulator you can trigger the alternator to see if it is working my guess is it is the wire coming from the ignition switch to the regulator pull all the connectors apart and clean with electrical cleaner and use dielectric grease to put them back together and use a ice pick or something stiff and thin to push all the pins in fully ptrobably just a bad connection. A good add on is a 10 guage wire between the alternator body and the battery negative especially in cold weather, larger battery cables help too.
http://www.therangerstation.com/tech_library/chargingsystem.htm