Hey guys Please help me out as much as you possibly can. this is my daily driver, it needs to be running. sometime between yestarday at 2:00 pm and now, 1:00 pm my alternator or something has gone wrong. I have a volt guage inside the truck, I noticed today that it didnt move when i started the truck, it went down as i cranked it over, but then nothing as its running. so its not charging. and yes I checked the guage, everything is securly hooked up.

recent problems: I have a tail light that does not work...I was messing with the wireing yesturday looking around to see if anything was loose....its not the bulb.

so since the buld doesnt light up, I just took it out....well I got back in the truck and started it up. a minute later i smell electrical fire...look around and see where is coming from, the trailer braking system box thing. well the last guy who had the truck used it. I never use it, and dont intend to use it, i dont tow anything big enough to use it. so I thought, ok well lets get rid of it. so i get some cutters and cut the wires going to it. tape those up and put the brake system in the garage.

start it up, and thats when i notice the volt guage.

I used a multi meter on the battery, engine off I get 12.40 engine running i get 12.40. so there is nothing going INTO the battery. I checked the wires going to the alternator, they are securly hooked up.

IAM TOTALLY STUMPED!

please help.

the last guy has this truck cazily wired. meaning there are a crap load of wires going everywhere...some hooked up, some not. and some just hanging. its a mess. I have no clue what to do.

bottom line is, the truck barely starts now, because the battery isnt getting charged. I have it hooked up to a charger right now though.

so, i guess the next thing to do is trace ever wire and make sure its going where it should...but where does everything go? its not just power and ground from the alternator is it? ther are 3 wires coming from the alternator....

maybe i should just start over and re-wire it myself? can some one give me some basics on where the 3 wires should go?

also, thers no fuse for the charging system is there?

and the alternator dosnt just "stop" totally does it? i mean can it just stop working one day?

the truck is a 1979 f150 custom 4x4. orignally had a 351m, now its got a 460. the last guy swaped it....

thanks a bunch for WHATEVER you can do. i will greatly appreciate it.

 

It sounds to me like the brake box may have caused a short in the charging system but your guess is as good as mine as to where this happened. You might start at the alternator and trace your wiring from there.

 

Trace any wire that is not connected to something and that looks like it is an added
wire for some long gone accesory and disconnect it at the power source. Any wires
that are running to a component like the brake controller/ fog lights etc. should have
a fuse as close to the battery as possible and you should stop right here and add a
fuse to any circuit that does not have one. To trace a short you could pull all of the
fuses out of the panel and just put the ones needed to run the motor and see if the
alternator comes back to life. Then while keeping an eye on the voltage start adding
one fuse at a time. The field needs to be excited on the alt. and if it's not then it
will not produce any voltage. Go to this website and find the wiring diagram that closely matches your s and tell us where you think the problem is. http://www.autozone.com/shopping/repairGuide.htm

 

Here's one of two possible diagrams for your truck. The first diagram is if you have a factory ammeter in the dash. The second diagram is if you have a factory "alt" or "gen" light in the dash(even though someone may have added a ammeter under the dash).





That was a good test you did with the meter on the battery, it's definitely not charging. The next thing to do is with the engine off, check for voltage at the rear output terminal of the alternator. If you do not have voltage, you may have a fusible link burned out, or a bad wire(I am not sure that had the fusible links in that wire on the early trucks)

If that tests ok, the next thing to do is take the "f" wire off the alt and tape it. Then get a scrap piece of wire and hook it to the "f" terminal of the alt, and then get the engine running, and touch this wire to the battery +. This will put the alt in full output charge, and you should hear it start whining, and the voltage should jump up. If it does, then your alternator is good.

 

ok guys. update.

this is the wiring diagram that iam going off of.

and Iam assuming the "starter relay" is the solenoid....






I got a new alternator, and a new voltage regulator.
still nothing.

I have it wired up EXACTLY like the pic above. I've cut and rewired everything to match.

Iam stumped as stumped gets!

I started it, and took out all the fuses in the fuse panel inside the truck.
still nothing.

the battery IS good, I know that.

oh and a little about the wiring...on the diagram, top right it says alternator regulator. it says A S F I....nothing hooks into the I slot. there is no wire for that slot, so we are not working with those wires.

is there ANYTHING else i can do? anything? any way I can do a "striaght shot" wiring? meaning is there any way I can bypass the voltage regulator, and all the other wires...? Iam sopossed to be driving this truck on a 600 mile trip in 3 days. Iam kinda up for anything about now. If you got any ideas, I mean any. please tell me. I really appreciate the help guys. I would love it if you could keep it up. thanks

 

Apparently you skipped over my post. If you do not have any wires on the "i", then the first diagram in my post is the one to go by.

Also I explained how you can for testing purposes, bypass the regulator by putting a wire from the "f" on the alternator directly onto the battery +.

If that test works, then there are a couple other things we can check.

 

O.K. frist you have to check to see that the new alt is putting out voltage ( new or rebiuld you can get a bad replacement )With a multi meter hook up to feed wire for the battery on the back of the alt this is usally the biggest of the wires and the color should be red make sure you have a good ground for the other test lead try to use a chasis ground (bracket or bolt but not the battery wire ground) Make sure all wire leads and connections are clear from all moving parts ( Belts , Pulley's ECT ) check the reading on the meter it should read at least 12 volts if you can have some one else start the truck and check the draw when the starter is engauged (reading lower the 8 volts could be a bad battery or wire) . When the truck is running the volts should read at least 13.5 volt but not more then 15 volts. If the volts do not go up to 13.5 volts the alt is not putting out. If the volts come up then alt and regulator is good and the next step is to check the voltage at the battery with the multi meter don't trust your dash gauge ( if it's a amp gauge it checks the state of the battery an bad cell will give you a bad reading!!) if the alt is putting out 13.5 and at the battery it is less then check for a good ground at the battery and to the chasis as well as to the alt if it has one. Don't assume because it's there it is good you could make a temp ground with a set of jumper wires one end of the black wire to the battery the other end of the black wire to the block and check the multi meter at the battery to see if there is a charge if still no charge then check the trace the positive lead (the big red wire ) from the back of the alt . Check and test all conections also look where the wires go in to the fuse block at the fire wall I have had older cars that the wire melted or broke under the hood at this connection this wire usually is red/green and is part of the ingiton system it is also a common place for someone to tap into for constant 12 volt power with key off . If all these areas are good then check the fuseale link but usally if the fuseable link is bad then the truck will not start .

You should not Hot Wire the alt to the battery with out the reg because this will keep the charging system in a full uncontrolled charge mode which means 15 plus volt at all times while the truck is running so once the battery reaches full charge ( 20 to 30 min in highway driving) you'll start over charging the battery and cooking the alt ( stray voltage from a over chaged battery can dammages many other sensors and over charged battery can explode with little notice!!!!) you need a regulator to switch the charging system on and off .

If the alt/reg are working and the Battery feed lead (the big red wire) at the alt reads 13.5 to 14.5 you could run a temp wire to the battery as a last resort to get the truck to the shop but in no means should this be done for nothing more then a short trip. This will bypass all wiring in the ingition system not the regulator

Do Not bypass the regulator by hot wiring from the Field conection (F term on alt ) to the battery for any lenght of time this also puts the system in full uncontrolled charge mode. Instead just take a reading with the multi meter

Good luck