1984 bronco charging system???

[wheelingbronco]

i have a 1984 bronco with the 4.9 I6 and it will start and run but there something wrong with the chargeing system cause all that my battery reads i 11.4

and i know that aint right so i replaced the alternator, voltage regulator, i checked the positive and negitive off the battery!! but still i only get like 11.5 and after i drive for a while i kills the battery!! please help!!

 

[shift1313]

check for clean terminals, good grounds, and check the wires going to the connector on the voltage regulator. Its happened before that you buy bad alternators right off the bat. Check the output of the alternator before the voltage regulator. On my 85 i was having the same problem and i had some bad wires going to the voltage regulator. I cant remember for sure but make sure the body of the regulator is clean and has a good surface to mount to. Im thinking its grounded through the body.

 

[Seabronc]

Im thinking its grounded through the body.

It sure does. Clean the back side of the regulator and around the ***** holes and then check the ground from the fender to the battery. If you use a volt meter from the fender, scratch a spot and place the - probe on the spot you scratched the + on the battery - terminal you should get no reading. If you do, you have a bad ground. Then go on to remove and clean the connections from the battery to the engine block and frame including the battery terminals, (they do corrode and build up a high resistance connection). After you do that check, for voltage between the engine block and the battery - as before. Clean a spot on the engine block, do not use the end of the ground cable as your test point. That ground cable is also suspect, they do go bad as does the cable from the battery to the start solenoid, (check for 12+ volts here, if the alternator is running you should have about 13.5 volts at the solenoid.

Good luck,

>-

 

[BroncoJoe19]

Seabronc,

I am trying to follow your reasoning here, could you please explain?

"It sure does. Clean the back side of the regulator and around the ***** holes and then check the ground from the fender to the battery. If you use a volt meter from the fender, scratch a spot and place the - probe on the spot you scratched the + on the battery - terminal you should get no reading. If you do, you have a bad ground. "

If one checks from the negative battery terminal to the body, I would expect one to get no voltage. IF one does get voltage there is a drain on the system. Now I guess that drain could be caused by the under the hood light if he has one. Oterwise he would have a short.. no?

WOuldn't it be better to use his ohm meter and check for continuity?

 

[crazyhorse85]

You could also check your voltage regulator plug itself could have a loose or even a broken wire in it....when i ha dthe problem with my lights flickering i found that it was a loose wire right in the plug itself and caused my charging system to pulse and cause the amps to bounce around it would go from 10.5 to 14 and back and forth....just a thought.... B)

 

[Seabronc]

Seabronc,I am trying to follow your reasoning here, could you please explain?

"It sure does. Clean the back side of the regulator and around the ***** holes and then check the ground from the fender to the battery. If you use a volt meter from the fender, scratch a spot and place the - probe on the spot you scratched the + on the battery - terminal you should get no reading. If you do, you have a bad ground. "

If one checks from the negative battery terminal to the body, I would expect one to get no voltage. IF one does get voltage there is a drain on the system. Now I guess that drain could be caused by the under the hood light if he has one. Oterwise he would have a short.. no?

WOuldn't it be better to use his ohm meter and check for continuity?

NO

I did leave out one statement, the ground for the regulator would require the engine to be running and the alternator putting out. The battery ground does not require the engine to be running. Having a voltage reading does not mean you have a current draw.

In both case you will get some sort of voltage reading if the grounding of that component is bad. It acts just like having a resistor in series and will show a voltage level. You are not looking for a full 12+ volts but any reading at all will indicate a bad ground. The effect on the component is that it will only see the difference, so if the ground resistance causes a 2 volt drop the component only sees the remainder.

So if I have 12V at the regulator and the ground for the regulator is bad, you should see a voltage reading between the case of the regulator and the battery - terminal.

Also, if the engine ground is bad, (the main ground for the vehicle) you will see a voltage reading caused by the high resistance between the engine and the battery - , you will get a voltage reading between a clean spot on the engine block and the battery - terminal. This is done with all connectiions undisturbed. If there is no reading then the ground is good.

Hope that helps you understand,

>-

 

[Seabronc]

OK, I went back and read what I actually wrote in the first post. I left out the check for bad regulator ground and skipped to the battery to frame ground.

Both checks are done without messing with the grounds until you know you have a bad ground.

As far as the regulator is concerned two checks are required, one from a clean spot on the fender to the regulator case (-) lead on the fender and (+) lead on the regulator case. A voltage reading means a bad regulator to fender ground. Again with the engine running.

Then if that shows no reading then move the (-) lead to the battery (-) post. A reading would indicated a bad ground someplace. Possibilities, battery to engine block, battery to frame, battery to fender.

The same for a battery to engine block or frame. A bad frame ground will show a voltage level between a clean spot and the battery (-) terminal as will a bad engine block ground. This can be checked with the engine off.

You definately need a digital meter, not an analog meter.

I have eliminated most of those poor grounding points by using ground buss connections which do not depend on the poor conductivity of steel for a couple of reasons:

1. Is an attempt to eliminate galvonic rusting

2. Improve the electrical function of various things like lights, power windows, gauges, etc.

 

[BroncoJoe19]

LOL... so now you got me going here...

I went to my EVTM and it stated:

Turn on the power to the circuit. Perform a Voltage Check between the suspected inoperative ground and the frame. Any indicated voltage means that there is a bad ground.

I understand that, but not how to test the batery cable if there is no drain.

SO I went out to my car to test.

I went from neg bat terminal to a ground on the fender... no voltage.

I then loosened up my neg bat cable and tested... still no voltage.

(as a side note... with the cable that loose, I really do not believe that enough amperage would get through to crank the engine)

I then disconnected the cable... I got 12 volts.!

Now that didn't make sense to me until I thought...

It seems to me that there is always a slight drain on the system, such as the computer keep alive memory, perhaps a clock, radio station memory, alarm, remote starter controls; stuff like that. All very very low amperage stuff. In my mind... if not for that, then one would not get any voltage even with the test I did by pulling the neg cable. I refer to an old test to see if there is something draining the battery, and that is to pull a battery cable and put a 12 volt light bulb with test leads between the cable and the battery terminal. If it glows, there is a drain. So those very low ameprage connections made the connection for the current to flow from the positive lead of the battery, through my volt meter, to the negative pole of the battery. Thus registering 12 volts.

It also seems that for one to get a drop in voltage, the ground would have to be pretty cruddy, and that one could still have 12 volts, but not allow enough amperage to flow through to be effective.

I think that I understand the confusion, in that a bad ground will not cause a current drain, in fact it will inhibit a drain. However there must be current flow in order for it to register on the voltmeter.

So in thinking this through...

If one has a good connection from the negative battery terminal to the cable and then to the block, when one probes with the voltmeter one should get no voltage at any of those connections. It seems to me that one would not get voltage at the fenders or the voltage regulator either, even if they were disconnected, because the current would flow through the good ground. OR there would be no current flow through the voltmeter.

Conversely if there is a bad ground, one would have to work his way back to the battery to find the closest point that he pulls voltage through the voltmeter. He would have to fix that one and then continue working his way towards any component he is trying to isolate.

I can see how if a component such as the fuel pump has its own power supply and its individual ground, that if there is a poor ground that if one probes it with the voltmeter, one is supplying an additional ground for current to flow through, and thusly it would register on the voltmeter.

I am missing though how this method would locate a poor fender ground.

Sorry Fred, this is an example how I drove my science teachers nuts. :wacko: For the most part your explanation was very good, and understandable. I guess I am just missing something. Thanks for trying /emoticons/[email protected] 2x" width="20" height="20" />

joe

EDIT: This may appear to be a little out of time line in that it took me two and a half hours to write this up between thinking, and work, and in the meantime Seabronc made and posted some additional clarifications.

 

[BroncoJoe19]

Wow... its been 30 years since I tested an alternator, but as shft1313 stated they can be bad out of the box. I don't know if they have changed much over the years, but I recall that my motors book had a method of testing it. THere are diodes (or at least were) as components and if I recall they could be tested individually. Diodes allow energy to flow in only one direction. I believe that if one crosses wires in installing an alternator, or jump starts someone improperly, that one can blow the diodes, and thus destroy the alternator.

Just a thought.

joe

 

[shift1313]

the biggest thing to remember about what you are measuring joe is open circuit vs closed circuit. If you were to check for continuity between the voltage regulator case and the - terminal on your battery even if there was a problem i would expect it to "beep" or ohm out. unless you had a broken ground or a completely insulated regulator.

Think about putting your multimeter on the two terminals of a battery that isnt connected to anything. you get 12v(roughly, actually 12.66 if its fully charged at 2.11v per cell) you are measuring an open circuit voltage(infinite resistance). If we start getting into technical terms you are measuring a difference in potential between two points.

so think about this. You can measure a voltage across your battery when the two terminals are not connected in a closed loop. So say you get a voltage between two "ground" points on your vehicle where there should be none, you have a potential between these two points which technically means there is resistance somewhere, and when you have resistance you have current. Because the ground circuit in a vehicle isnt shut off with the key, when you have a resistance in the circuit somewhere you get a drain.

Here is another way to think about it. If you connected a cable from your + on the battery to the - technically on current would flow because there is no resistance(technically). You need resistance to have current.

If you want to get into basic electrical theory about this stuff look up thevenin and norton equivalent circuits

 

[BroncoJoe19]

Matt,

Thanks for the attempt.

I guess I need to look up the definitions of current and ressistance.

My concept is that current is the flow of electrons, and ressistance is ressistance to that flow.

An ohm meter is used to measure ressistance. WHere the ohm meter supplies the current to be measured.

A drop in voltage is a result of ressistance to the flow of current (supplied by a source extenal to the voltmeter, such as the car battery)

If there is current flow, the battery is being drained, (whether it is the battery within the ohm meter (when measuring ohms), or the car battery when using a voltmeter (and measuring volts)).

So there must be current to measure ressistance.

 

[shift1313]

the most important thing to know about analyzing electrical circuits is V=IR(voltage = current X resistance). If you had a circuit with no resistance, there would be no current flow because there is no need for current flow.

i know a lot of people relate electricity to water. think about the water in your house. The water supply is the + and the sewer is the -. when all your faucets are shut, no toilets going you have no water BUT if you had a pressure gauge on your line you would have water pressure. So the Pressure is your Voltage and the flow is your current.

on the subject of finding a bad ground. If you have a good ground you should see no "potential" between the voltage regulator housing and the body. If you do then you in fact have a resistance which goes back to v=ir. Also electrons flow from - to + so if you add resistance in your ground circuit which should have next to no resistance you are sucking power. Im not exactly sure how the voltage regulator circuit is on the ford but if bleeds the excess voltage back through ground this would also help indicate an issue.

ill have to think on it a bit more as im in a hurry so i probably missed the boat on this one