Take a quick look at fuse 6 in the power distribution box, if it's blown it wont charge.

If the fuse is good it looks like you need a new alternator.

 

ended up replacing the alternator. got a brand new one from the dealer ($175) and installed it. for some reason the voltage gauge doesnt match the reading taken with the microvat. microvat shows everything working properly and good voltage numbers throughout the range, but gauge shows low, near the L, most of the time. dont know why. faulty gauge? it didnt do this before it rained.... havent replaced the belt yet, will do that this coming wednesday. thanks for your help....

oh yea, forgot to check the fuse... will do it when i change the belt. but i dont think its blown because the battery showed good before and after the alternator replacement.....

 

Start it up & connect your voltmeter to the battery, does it read approx 14 volts?

A fully charged battery will read around 13 volts. So if your reading is 13 volts or less it isnt charging & you need to check that fuse.

 

i've never ever seen a battery show 14 volts at idle.... only when cruising... but i will check tonight with a voltmeter. (wife has the truck at work).

 

alright, the only meter i have is an analog from a long time ago. my digital isnt working. they are so different, not sure on how to use it. i have a 1000v, 150v, 15v, K(omega), 150mA, DC(omega), and AC-V settings. there is no dial, the leads just plug into which hole you want in the meter. i have the positive lead plugged into the 15v hole, but not sure where to connect the negative lead. i tried using the DC(omega) hole and measured 13 volts on my toyota with the car off. turned the car on and it went to 15+ volts. i dont have my truck until later tonight. is this the right way to do it?

 

sounds like you did the right thing. The only thing I would recommend is that you start at the higher range setting (in this case jack into the 150V location) first. Then you confirm that it is indeed not above the next range down (i.e. not higher than 15V) and you can move the lead to the other location and remeasure. In this way you avoid "pegging" the meter and possibly damaging the circuitry inside.

 

What K2JJB said. Also, you noted that you haven't seen a system run at 14V at idle. They can. I notice your Avitar is a foxbody 5.0. If you're used to looking at a Fox with underdrive pulleys (a common mod), it typically will not run 14V at idle, cause the alternator has been slowed down in relation to the engine speed. Also, if there are electical components running that pull a significant current drain, like fans, defogger grids, head lights, big sound systems, etc., the voltage will be lower at idle because the alternator is unable to supply sufficient amps at the low RPM's. So make sure all electrical accessories are off when you first test. If voltage is OK, then you can turn things on and check voltage with more current draw. Also, from the diagram located here http://www.autozone.com/images/cds/g...3d800ba9ec.gif , Fuse #6 (15 amp) supplies power to the field so the alternator can charge and 2 12 Guage fusible links in parallel supply power to the the battery from the alternator. Failure of the fuse or of both fusible links could stop the battery from recieving the appropriate charging voltage.

 

alright, i checked it with the multimeter. i'm showing the same reading with the truck off and on. about 12.6 volts. i checked fuse #6 and it was good, replaced it anyway with another 15 amp and same result.... not sure on how to check the fusible links.... i'm wondering now how the heck can it be such low voltage?? could a bad belt cause this? or a slow-moving belt? I noticed it doesnt move very fast.... i'm replacing the belt this coming wednesday, but that wouldnt fix the speed of it. not sure on how fast its supposed to be....

 

Find the large wire (output lead) on the alt and measure voltage at that point. It should be around 13.8 volts if the alt is charging. If it is, then re-measure the voltage at the battery. Is it lower than the alt output post? If so, then the fuseable link between the alternator output post and the battery is "open". If it is the same, and below 13.8 volts, the alt is not charging correctly.
Not sure how your vehicle is wired, but on my 91, the fuseable link was in the alternator output lead, spliced into the wire at the point where it connected to the starter solenoid on the inner fender. From there, there was a lead running back to the battery to complete the charging circuit. Repair required that I procure a length of the correct fuse link wire (from a local auto electrical repair shop) and splicing it into the alt output wire where the old one connected. Also had to install a new 3/8 inch stud "O" ring wire connector for the solenoid termination point.

Dialtone

 

Or, check voltage at the Gray wire at the starter relay. If you see 14 volts there, replace the starter relay.

The starter relay is just under the hood/drivers side fender with 5 wires attached red/light blue, red, 2 black and gray

On this one the fuse links are external.

Edit: If you see 14 volts on the gray which is the feed from the fuse links but you dont see 14 volts on the red which connects the starter relay to the battery, replace the starter relay.

 

The battery + cable and the grey wire from the alternator should be on the same terminal of the starter relay. The charging current should not pass through the relay in any manner as the wires should be joined together on the same terminal, so the relay shouldn't be an issue for charging. If you don't have charging voltage on the alternator to the Black/Orange wire, you need to check for 12V at the Yellow/White wire. Also check fuse 15 (7.5 amp) as it supplies excitation voltage from the ignition switch through the Light Green / Red wire. If the fuses are OK and the voltage still doesn't look right, you could also have a broken wire.

 

alright this is weird. i'll tell you what i just did. i measured voltage as soon as i started the truck and it came up with about 12.1 volts, then i waited until it warmed up a little and then i took another reading, about 13.5 volts. what changed? does it need to warm up? I then turned on all conceivable things (brights, windshield washers on high, fog lights, radio, rear defroster) and it wouldnt drop below 12 volts. it was about 12.2 volts. i then turned all of this stuff off and back to just a warmed up truck and the reading was about 13 volts. i then measured voltage at the gray wire on the starter relay and get the same reading as i do when checking it at the battery. i just touched the positive lead to the bolt and nut that is clamping down the gray wire. btw, i have 2 medium thickness gray wires, a big thick black wire, a red/gray wire, and just a red wire which goes by itself with a banana plug or something. the 2 gray wires and i forget which other one(s) were all punched down on 1 bolt. so i dont know if this was the correct way to measure. what does this sound like to you guys?

for reference, i check voltages using the 2 battery terminals.

 

That looks like battery voltage & it's still not charging.

Not sure what I was thinking earlier, but as Jerry sez & as you noted the gray, black & red wires are all tied together at the same terminal on the starter relay.

As Jerry said check that interior fuse 15.
it's wired to the "charge warning indicator"/idiot light on the dash & then to the voltage regulator in the alternator.

 

fuse 15 is good.... can it be that whatever supplies the gauge is bad and everything else is ok? or are my voltages still off? i will take a reading again this morning to make sure of the numbers....

 

Not sure which guage you mean may be bad. Instrument cluster voltage? If so, is it moving at all? If it's moving any, then the connections are at least there. Definitely check the voltage with an independent meter. You mentioned earlier about not having a digital meter, you can get a decent cheap one at Walmart or Radio Shack or a number other chain stores for around $10 or less. Make sure you get one that has resistance measurement as well ( ohms ). Then you can check the wiring for continuity and bad connections.