Charging problem

[phat46]

I have a Ford that's not charging. A 70ish three wire alt.  It was fine but I took it off to grind a touch off the cooling blades because they were slightly rubbing the frame. I put it back on and now it won't charge. If i rev it the idiot light will fade but then come back bright when the revs come down. All the connections are back where they came off of and they're tight, at both ends. Do these need to be polerized? I don't think they do, but if i really knew I wouldn't be posting here would I???  

[tom36]

You do not polarize alternators-- generators, yes but alternators, no.  Tom...

[wayne petty]

I have a Ford that's not charging. A 70ish three wire alt.  It was fine but I took it off to grind a touch off the cooling blades because they were slightly rubbing the frame. I put it back on and now it won't charge. If i rev it the idiot light will fade but then come back bright when the revs come down. All the connections are back where they came off of and they're tight, at both ends. Do these need to be polerized? I don't think they do, but if i really knew I wouldn't be posting here would I???  

wires on the back of ford alternators are

Bat.  this as stated goes between the back of the alternator and usually the battery side of the starter relay/solenoid

fld   this is the field wire. it goes throough the brushes and powers up the rotating rotor.    the wire comes from the F term on the regualtor.  and is pulsed by the regulator to change the output of the alternator.   by disconecting the regualtor and on fords jumping from A to the F  on the regulator pigtale you can tell if the alternaotr is working as it should almost instantly go over 15 volts... do not do this for more than a few seconds..

STA    this is the stator terminal.   it will have half the output voltage of the alternator when the alternator is charging. """only when the alternator is charging."""" this terminal hooks to the S term on the voltage regulaotr and let the regulator know what or how fast the alt is turning..   it used to make a mechanical contact viberate. but there are probably not that many mechanical regulators left.    you can test this with a volt meter set at 20 volts A/C  with the alternator charging or during full field test...

there may also be a ground wire on some applications. to ground the regualtor to the case of the alternator.  this prevents overcharging and under charging do to voltage drops through the system.  see volt drops below

if any of the wires is broken and they do break the alternator will not work. use the continuity beep on your digital volt meter to test them with the car battery disconected...

(digital volt meters can be had for under 5 bucks all over the place...)


charging system specs

charging systems must be tested with the battery at full charge...

batterys are tested with everything turned off and the engine off.
turn the head lights for one minute then off. this removes the surface charge.

now with the volt meter set to 20 volts D/C  

12.65 volts is 100% charge
12.45 volts is 50%  charge
12.25 volts is 25% charge

you cannot get an accurate reading with an analog meter. that is for testing

once you start the car and the battery and hte battery has tested close to 100% charge

the output voltage should be

14.1 to 14.5 volts d/c

if it is under check for loose belts. or bad alternators.

what ever you do never never never pull the battery cable off to test the alternator..
the battery loads the alternator and keeps the output voltage from going out of control.. the diodes in most are  25 amp 100 volts PIV (peak inverse voltage) the alternator going without a battery can get to the voltage for a millasecond and blow out or weaken the diodes.  it may fail at a later time... kinda like revving the motor in park to see if the valves are going to float. over stesses componants....

jump starting a car with a dead battery does the same thing.  puts a huge load on the alternator. then the other car trys to crank.. the alternaotr trys to put out that amperage... overheats / overstresses the diodes.

proper way is to charge the dead car for 10 minutes. then turn off your motor leaving the cables attached.  and the car will start.

you can only damage the alternator with the engine off if you hook the cables up backwards... the fuseable link goes if you have one... if you dont then the diodes...

should i continue...??


does everybody know what a voltage drop test is..

volt meters test the differnce in voltage between where you test...

#1:  across the battery you will see 12 to 14 volts dc..

#2:   battery  (-) neg term to engine block with the engine running.. less than .02 volts d/c  over that look for a bad ground wire

#3:   Battery  (-) to the body or frame. engine running all the head lights on..   less than .02 volts D/C


#4    battery (+) positive term to the alternator output. this may be a little higher like .08 volts D/C


if you see any thing over 1 volt you have a serious problem... like a loose connector, bad krimp, freyed wire, corrosion in the mechanical connection..

wire brush the faces of the terminals if they are dirty at all...

lead and the zinc coating oxidizes and becomes lead oxide or zinc oxide. both are ceramic and insulate.  thats why the crust on the battery posts is crunchy.


do feel free to edit this if i have posted something wrong..


wayne...

[GPster]

It was fine but I took it off to grind a touch off the cooling blades because they were slightly rubbing the frame. I put it back on and now it won't charge.

Two wonderings. Did you get any grinding dust in the alternater? That might have set up a short. Is there anything magnitized in an alternator? I have seen ( a friend's seventh grade science fair project} magnitizim upset by something like a grinding motion. I vote that the previous explanation be submitted to the tech file to solve future problems. GPster

[phat46]

It was fine but I took it off to grind a touch off the cooling blades because they were slightly rubbing the frame. I put it back on and now it won't charge.

Two wonderings. Did you get any grinding dust in the alternater? That might have set up a short. Is there anything magnitized in an alternator? I have seen ( a friend's seventh grade science fair project} magnitizim upset by something like a grinding motion. I vote that the previous explanation be submitted to the tech file to solve future problems. GPster

I thought of that before I ground the tips of the fan and i was carefull to grind away from the alternator while grinding, but it's still a possibility. I checked it for output this morning and it's not charging, so for whatever reason i need a new one, or a rebuild on this one. I don't think this truck wants me to drive it. i had the trans rebuilt and had just installed it when this happened. I think the trucks afraid i will do all the things to it that i threatened while overcoming all the crap during the build!      

[C9]

Make sure you haven't loosened the nut that holds the terminal post to the alternator.

Sometimes these will back off when you unscrew the nut so you can remove a wire terminal.

[wayne petty]

I have a Ford that's not charging. A 70ish three wire alt.  It was fine but I took it off to grind a touch off the cooling blades because they were slightly rubbing the frame. I put it back on and now it won't charge. If i rev it the idiot light will fade but then come back bright when the revs come down.


a thought just hit me
did you remove the fan from the shaft???  what did you use to remove the nut and to install it....3/8" allen and a box end wrench or an impact of some type?

if you removed the fan from the front,  the rotor shaft may have slipped back in the bearing while it was apart. the comutator may be grooved or dirty and the brushes may have become damaged or coated with grease....

also did you tighten it with an impact? that is teh proper way to do it.. just doing it with a wrench  may allow the pulley to slip on the shaft and cause the failure you describe...

60 amp alternators take almost 5 horsepower to turn at max charge... this is why drag racers has a switch to shut off the  alt during a run.

do you know about the thumb belt tention check/ajustment just for alternators with external blades..

the belt needs to be just a little tighter if you can push the alternator blade/pulley around without turning the crankshaft...

WITH THE KEY OFF GUYS....

too tight will cause the waterpump or alternator bearings to fail sooner

i'am all charged up with desire to know what happend.....

[phat46]

I just got back from a real good starter/alternator/generator/etc. rebuilder and he tested the alt and showed me that it was working great; 60 amps and about 18 volts when he did the feild test on it. sooooooo....my problem is apperently downsteam from there....I'm on it.  

[phat46]

UPDATE;  I re-installed alternator and it's charging fine.... :?  I hate it when that happens.......

[Crosley.In.AZ]

UPDATE;  I re-installed alternator and it's charging fine.... :?  I hate it when that happens.......

so you hoooked it up wrong the other time ?

[phat46]

UPDATE;  I re-installed alternator and it's charging fine.... :?  I hate it when that happens.......

so you hoooked it up wrong the other time ?

Nope, same three wires, same terminals.........I don't really care 'cuz now it's charging and I took it out and beat on it...

[Mikej]

Could it have been a ground problem?

[phat46]

Could it have been a ground problem?

Coulda been, but I didn't do anything to improvve the ground either; it has two bolts running trough the alt. into the block and two more through the bracket into the block and the block is grounded by a strap to the frame which has the neg. cable from the battery bolted to it.

[Crosley.In.AZ]

ah.... an intermittent problem.  They are the most fun

[kb426]

For a change. it wasn't a "team smart" member helping out.