Bad alternator?

[camper4lyfe]

Here's a strange one for you, folks.

I've been on vacation for the past 2 weeks, so my truck's been sitting for somewhere between 2.5 and 3 weeks (the wife and I commute together in her car for the gas mileage).

I went to run out to grab some grub tonight in the truck (03 FX4), and when I started it, it did a couple strange things. It seemed to rev really high right off the bat, but came down and ran normal. Also, the battery light came on, and the voltmeter/gauge is reading REALLY low.

I've got a Haynes manual, and I went through some of the tests as best I could (it's really confusing) and it's leading me to believe that the alternator's bad. The battery reads 12.4V when it's not running, but something like 11.9 while running, no matter what rpm it's at. I've noticed recently that the voltage fluctuates while driving based on RPM and engine load (idling with the AC on drops the voltage quite significantly).

Am I reading this right that the alternator's bad? In the end, I guess it doesn't matter if it's the alternator or the regulator because it's an all in one unit.

So I guess I have 4 questions:
1) Am I figuring it right that the alternator's bad? (I plan to have it load tested first)
2) Should I replace the battery as well? (Should I just have it load tested too?)
3) Would the alternator go bad just from sitting?
4) What's the amperage of the stock alternator/does it matter if I run a bigger one than stock? (I'm seeing 90A and 95A listed to fit)

 

[bilzy7]

Things break, if it's running still and starting up I'd assume it was charging but not putting out enough. I mean obviously if it was completely dead the battery would go out within a couple mins without constant charge from alt. Bigger amp is for more accessories I believe such as a 5.0 having a 130 amp in an explorer with all the additional lights it has inside and such.

 

[shane96ranger]

It sounds to me like your alternator took a dump by your description here:

The battery reads 12.4V when it's not running, but something like 11.9 while running

Your truck is running off of the battery if you are decreasing volts while it's running, and will eventually die. I wouldn't be running around town like that, it's not especially good for the battery.

Get your alternator load tested, and I'm betting it fails.

 

[camper4lyfe]

It sounds to me like your alternator took a dump by your description here:



Your truck is running off of the battery if you are decreasing volts while it's running, and will eventually die. I wouldn't be running around town like that, it's not especially good for the battery.

Get your alternator load tested, and I'm betting it fails.

I tried really hard to not run the truck any longer than I had to in order to do a couple tests. I'll be sure to throw the battery on a charger before giving it a go with the new (most likely) alternator.

 

[camper4lyfe]

I had the alternator rebuilt ($81), and they obviously didn't test it because that didn't solve my problem.

I had the battery tested, and although the amperage rating is low, it's still "ok" and most likely not my problem.

This leads me to believe that the fusible link is bad, but I can't, for the life of me, find the blasted thing. Where is it, what am I looking for?

It's an 03 Ranger with the 4.0L V6. Pictures, a general idea of where to look would be greatly appreciated.

On a side note, while looking for things, I found this. What is it? It's in the fuse box under the hood, but has no continuity, as if it's a bad fuse.

 

[Ronv]

The item you are holding hasa ,"diode" symbol on it. It passes current in one direction but not in the other. If you are using a multimeter to test it try reading in one direction and swap the leads and you should get continuity one way and open in the other.

Good luck

RonV

 

[Earl43P]

PCM Power diode.
It won't start or run without that.
Has nothing to do with the alternator issue.

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

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



S And I Circuit Test - Integral Voltage Regulator

37. Disconnect the alternator electrical connector.

38. Connect one jumper wire from the alternator A terminal to its corresponding terminal in the electrical connector. Connect another jumper wire from the regulator F screw to the alternator housing.



(Illustration CHS8)


39. Start the engine and let it idle.

40. Connect the voltmeter negative lead to the alternator housing. Connect the positive lead to the connector S terminal and I terminal in turn (see Illustration CHS8). Voltage at the I terminal should be approximately double the reading at the S terminal.

a) If the readings are as specified, replace the regulator.

b) If there is no voltage, check the wiring for breaks or bad connections. If the wiring is good, replace the alternator.


I believe they've gotten away from using fusible links on the alternator cable in favor of the MaxiFuse.

 

[camper4lyfe]

PCM Power diode.
It won't start or run without that.
Has nothing to do with the alternator issue.

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

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



S And I Circuit Test - Integral Voltage Regulator

37. Disconnect the alternator electrical connector.

38. Connect one jumper wire from the alternator A terminal to its corresponding terminal in the electrical connector. Connect another jumper wire from the regulator F screw to the alternator housing.



(Illustration CHS8)


39. Start the engine and let it idle.

40. Connect the voltmeter negative lead to the alternator housing. Connect the positive lead to the connector S terminal and I terminal in turn (see Illustration CHS8). Voltage at the I terminal should be approximately double the reading at the S terminal.

a) If the readings are as specified, replace the regulator.

b) If there is no voltage, check the wiring for breaks or bad connections. If the wiring is good, replace the alternator.


I believe they've gotten away from using fusible links on the alternator cable in favor of the MaxiFuse.

Unfortunately, I'm unable to do these tests as I don't have any jumper wires.

I did some tests tonight, and it just seems as though the alternator's not charging at all. There's no voltage change at all when the engine's running. Well, there's a change....down. I'm taking the alternator back to the shop that rebuilt it to get it looked at again.

I talked with my father-in-law (a retired mechanic), and he says it should have a magnetic field when it's running, and I get absolutely nothing (move a wrench around it, and there's zero pull on it).

 

[sheltonfilms]

See if these help:
They are from the Ford Service Manual for your year.

 

[camper4lyfe]

See if these help:
They are from the Ford Service Manual for your year.

Of the 4 tests, I did 3. The biggest thing I noticed is that while running, the voltage drops below 12 and doesn't change with engine speed.

 

[camper4lyfe]

I went back to the shop today with the alternator. On the way there, I stopped by an Autozone to have it checked as well. At Autozone, it failed, though it was stated that their Ford plug was bad. At the shop, he tested it and it was putting out 14.4V. While there, he gave me a quick rundown of the wiring for it and gave me a different wiring diagram from the one that's in the Haynes manual (I'm really not a fan of that manual, but it's better than being completely in the dark).

There's got to be something up with the wiring in my truck. My first guess is fusible links, but how do you test them without cutting things open? The way they're wired, continuity tests don't really do any good. The only other thing I can think of is resistance, but I wouldn't know where to start looking for what the resistance SHOULD be. Any thoughts?

 

[sheltonfilms]

I went back to the shop today with the alternator. On the way there, I stopped by an Autozone to have it checked as well. At Autozone, it failed, though it was stated that their Ford plug was bad. At the shop, he tested it and it was putting out 14.4V. While there, he gave me a quick rundown of the wiring for it and gave me a different wiring diagram from the one that's in the Haynes manual (I'm really not a fan of that manual, but it's better than being completely in the dark).

There's got to be something up with the wiring in my truck. My first guess is fusible links, but how do you test them without cutting things open? The way they're wired, continuity tests don't really do any good. The only other thing I can think of is resistance, but I wouldn't know where to start looking for what the resistance SHOULD be. Any thoughts?

Ummmm those test I gave you, test this.

Did you do the tests like a flow chart? Like if the first text is NO then its the wiring.

what are your results?

 

[camper4lyfe]

Ummmm those test I gave you, test this.

Did you do the tests like a flow chart? Like if the first text is NO then its the wiring.

what are your results?

I wasn't able to test until just now.

For B1, I got a battery voltage of 12.66 and a reading of 12.66
B2 Got a reading of 12.14
B3 had a battery reading of 12.4 and a reading of 12.27
B4 is the one that throws up a red flag. I got a reading of .01.

The problem with B4 is that I know the alternator's good, but the result says replace the alternator/generator, correct? I'm at a loss as to what to do next.

 

[sheltonfilms]

If it was me I would have that alternator checked again at another Auto Parts store. If that one you went to is the only one, tell them to run the test again except this time with one they have one the shelves. If the one off the shelves passes then you definitely have a bad one.

 

[camper4lyfe]

As a follow up/conclusion to this problem:

My father-in-law took my truck over to the shop today, as he's retired and has the time (and knows more about what he's talking about than I do). As it turns out, it was a bad connection at the end of the fusible link. The end of the wire was corroded and the tech was able to just pull the link out. $15 later, it's "fixed" enough to work for now, but I still need to permanently fix the other 2 links that go into that connecter, as corrosion on 1 wire=corrosion on all the wires.

What my biggest stumbling block was the fact that I was using a DMM instead of a test light. The wire had enough connection to pass the voltage through (though slightly lower than battery, which should have been a clue), but not good enough to pass the amperage necessary to trigger the voltage regulator to work.

I'm slightly annoyed that the shop rebuilt my alternator without testing it first, and got a "free' $81 out of me, as I'm quite sure that the alternator was not bad from the beginning, even though the tests showed that it was.