90 5.0 alternator charging problem

[jr78f150]

Newbe here,ive got a 90 5.0 that i cant get to charge. at first i figured a new alt. would fix the prob. with no luck but it didnt.i messed with it some,traceing some of the wires and checking what fuseable links i could find. does anyone have a link to a really good alt. wireing diagram or have any ideas on where to start? i took the new alt. back to make sure i didnt get a bad one so thats not the problem.ill do some searching around on here but thought maybe someone else might have had this problem in the past. need to get this thing fixed ASAP,its been down for about a month (havent had much time to work on it) and spring is here so im haveing very bad 5.0 withdraws lol
J.R.

 

[ratio411]

Do you have a test light?

You can test your wires on each side of the fuse-links to make sure they are all good.

Also, I know that dirty or loose connections at the cables (battery and solenoid both) will keep a Ford from charging, even though it might start and run seemingly fine. My 90 F150 is terrible about this. I have to clean the connections every month or so, even if it seems to run fine. It will slowly reduce charging to the battery as small amounts of corrosion build up.

With good connections, you just need a constant hot cable going from the battery side of the soleniod to the alternator. Then there are 2 wires traveling from the alternator to the regulator. A 3rd wire goes to your idiot light and a 4th yellow wire on the regulator is constant hot.

I hope this helps some.

Make sure you have power to the cable on the alternator, and that the yellow wire on the regulator is hot as well. If so, then your fuse-links are okay. If the alt is new, the hot wires are hot, and the connections/cables are tight and clean... then I might suspect the regulator.

 

[jr78f150]

heres more info

thanks for the help Ratio,ive been reading old posts for almost 3hrs and have come up with several thinks to check and your wireing info will help. there are alot of posts on this issue but nobody posted the fix lol.its been about a month since i messed with it or longer (got alot of snow and bad weather in Feb.) so i had to do some thinking on the things ive tried.buy the way,i have a gauge instead of the light.several months ago i unhooked the pos. battery terminal while running and it accidentally fell and grounded itself out for a split second which didnt cause problems at the time but im sure is the culprit for the problems now.after installing the new alt. i put new solder on battery terminal ends,changed battery,ignition switch (electrical part but not the key part),the alt has a built in voltage regulator so it is new along with the alt.,i checked the fusible links but will check them again tom. while checking the wireing now that i know what is it and have found a wireing diagram.the original alt. was bad when it was tested and this is my second new one. the first new one was assembled wrong and although i was able to install it the plugs (which should eliminate and crossed wires) where on the bottom and impossible to get to without removeing the alt. what im wondering is what all the grounded pos. terminal could have caused to go bad? ill be checking everything ive put on my list tom. but any other suggestions on things that could have got fried when the terminal got grounded would be great. like i said,it was fine for 6-8 weeks after that happened but most likely that caused this mess. its also mostly stock so there arent any electrical things that should be pulling more than stock voltage. also,even before the terminal got grounded my heater blower motor would sometimes blow strong and other times blow kinda weak but i think it actually a problem with the ductwork or something instead or the motor itself. also,the plugs on the alt. look fine,they arent all burnt up or corroded.im sure ill remember more stuff ive checked/fixed and will post them up as i remember them or someone mentions them and ill be sure to post the fix when i do find it incase someone in the future has this problem
thanks,J.R.

 

[HISSIN50]

On the regulator are terminals labeled A, S, I.
A = battery voltage.
S= ~1/2 battery voltage while the car is running.
I= excite. If this circuit is open, the alt will not charge.

Look in the lower right hand corner of this diagram for the alt circuit.

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

If you're sure the blower motor is not the cause of the weak flow, look for a vac leak in the vacuum lines for the HVAC system. If there's a leak, it will cause all the air to go out the defroster vents. This is a common issue. Just trace the line labeled AC (at the vacuum tree) along its path.

Good luck.

 

[jr78f150]

did some testing

the green wire with red stripe going from alt to voltmeter is only showing 2.8volts at the alt and behind the inst. cluster with key in run position and not running. on the other side of the resister its showing 11.7 volts. could the gauge or this resister be my problem?

 

[HISSIN50]

That's fine. ^^