I have a 98 Ford Ranger 4.0. The other night my battery light came on and my altenator started making noise. I replaced the altenator with a Autolite altenator from Kragen and I also replaced the battery. My battery light is still on and while driving today my truck died and my battery is dead. After reading in the forums here it seem like allot of replacement altenators are defective. If not that what else could be the problem? Could it be the regulator and if so where is it located on my truck? Thanks

 

Loose bad connections,bad voltage regulator,bad alternator,I would have your replacement tested at another auto parts store.

 

check all connections for corrosion and that they are tight-only other thing i can think of is the alternator is bad

 

If it died while in motion, then it is your Alternator or Belts. The battery is dead as a result of the Alternator not doing it's job. Sounds like you already knew this, but I'm confirming for you.

I too would check all connections, but it's probably just a crap Alt.

 

There's a remote possibility of the fuse links going out. There are two in parallel in the harness to protect the alternator. You'd have to lose both of them to have the alternator stop charging and about the only way that happens is with a high power drain or short circuit or bad starter and so forth.

If you can get a digital voltmeter, you don't have to make any assumptions about is it charging or not. Alternators should put out something liess than about 15 volts, and something more than about 12.8 to be charging. 13.8 is considered "nominal" and 14.2 is about right to keep a battery healthy long term. Seeing anything less than 12.8 with the truck running (and this would be with lights on and so forth) shows you aren't charging much or at all.

Alternators are heat-throttled though. The regulator reduces the charge voltage as the alternator temperature increases. You'll see your highest voltages after a cold start, and your lowest after the vehicle heats up. This is independent of load -- load changes obviously will change the voltage.

You can have a bad battery with such a low internal resistance it's dragging down your alternator. I recommend having the battery checked using a battery tester as well before dumping another alternator in there.

 

I'va had the altenator checked twice and it's putting out something like 14.8 volts and like a said the battery is new. If the belt was loose wouldn't I hear a sqeeling noise? I'm stumped.

 

If you have a 12V test light or volt meter you can do some simple checks:

1. With the Ign off check for power at the Alt B+ wire (BK/OG wire). If not, check for open circuit or blown fusible link between the Battery and Alt.

2. With the Ign off unplug the wiring connector at the Alt and back probe pin 1 (YE/WH wire). There should be power. If not, check for open circuit or blown fusible link between the Battery and Pin 1.

3. Turn Ign on and check for power on Pin 3 (LG/RD). There should be power with the Ign on. If not check for a bad fuse in CJB.

If all these check good, then either somethings wrong at the plug and one of the wires are not making a good connection or you got a bad alt from Kragen's.

 

What I have done so far is:
Replaced the Alt and battery
Had the new alt tested a Kragen (putting out 14+ volts)
Tested the voltage at the battery (Only putting out about 11.5 volts)

 

sounds like you got something pulling voltage somewhere,done any electronic work lately?

 

I found the problem. It was a blown 30amp fuse in the fuse box under the hood. Thought I checked all of them but I must have missed it. Next time I check for burned out fuses I will be sure to wear my glasses. Thanks for all of the help.

 

Where are the fusible links. I think this is what is wrong with mine I put 2 new batteries and 2 new alternators. I have tested all relays and all connectors and still my alternator will not charge the battery. Also my dumbass accidentally hooked terminals up backwards on the first battery so I feel like I definitely popped the fusible links but wiring diagram doesn't show the links. Its a 2000 ranger 2.5 l. 4 cyl. Also the batteries are 540 and the original one was a 610 would that have anything to do with it?? Please let me know I am stranded. Thank you