Someone explain the charging system please

[99ss]

1970 b body 440 in it MSD ready to run ignition...

batt dead wouldnt start... lights were flickering for a few weeks before it finaly died... new alternator.... was a new volt reg... I take a multi metere and ground it to the fender and touch the lug on the alternator that goes back to the batter and I get like 8-12 which is what it reads at the battery no running...

how does this car charge the battery? the two small leads attach to what says field on the alt and thi big on goes to the batt...

can the voltage regulator be bad? how often do they fail?
car was running great and now this.. starting to piss me off and give me bad feeling towards mopar :tied up:

 

[70rr-brian]

8-12v at the alternator is too low....should be around 14v. the battery should be at 12v give or take a few decimal points. If the car is running with a healthy alternator you should be able to pick up roughly 14v at just the battery terminals. The alt should be pushing 14v+ to the battery to keep it charged. Getting a bad "new" alternator isn't just a mopar thing. Its a quality control issue for the remanufacturers.

 

[99ss]

what about the voltage regulator? how does it come into play I just picked up a new (reman) alt again and get the same reading.. two bad alts in a row? the car will run off the batt just fine on a quick trickle charge so I think the batt is good

 

[70rr-brian]

http://www.mymopar.com/charging.htm

 

[oxytousc]

Yea. If you're testing the alt off the lug on the back, the voltage regulator shouldn't even come into play. I'd recommend buying one of the alternators that have a lifetime warranty.

 

[99ss]

luckily I did.....LOL

So if the field wires were backwards would that effect it ? Does it have to flow in one direction only?

 

[67 B-body]

Do you have voltage at the + field terminal on the alt? If so, how much? Is the voltage regulator grounded well? Do you have the body ground strap hooked up? It's not a manufacture thing.... Electricity works the same no matter what the brand name.

 

[Meep-Meep]

How this works is the voltage regulator FLD terminal supplies voltage to the FLD terminal of the ALT. By doing so the magnetic "field" of the rotor gets stronger as more voltage is applied to the FLD and that is what increases output. The big breakthrough with the alternator is the high current doesn't come from the rotor and through the brushes like a generator, thus having a much longer life then the generator. The alternator is also an AC device, hence the name, and the output is rectified with big diodes to produce DC.

To test the output of the alternator put 12V from the battery to the FLD terminal on the ALT (with regulator FLD disconnected) and watch the volt meter. This is called full fielding the alternator. If it's putting out you will have a steady rise in voltage capable of going well past 15V so don't hold it too long.

 

[99ss]

Tried it and the same thing.. just above 8+

Ok ,maybe I should have said get bad feelings towards this car and not branded it...LOL

(with regulator FLD disconnected) ?? you mean the green wire? the blue is the exciter from the ign and + terminal

I'm going through the whole system today.. new vlt reg, new pigtail.. checking the grounds.... it was working fine it seemed..
I can run a wire to the + of the battery and using my test light get a good connection (good light) anywhere on the car so it has to be grounded good.

I need this car to run tonight with my kids in it so this has to be solved today

 

[70rr-brian]

Try disconnecting and cleaning your bulkhead connectors just for fun while you are messing with it.

 

[Ron 73]

I would check all the connections related to this, any corrosion can cause a problem,.. You said the bat will work on a trickle charge, id also check each cell in the battery with a hygrometer if you have one, maybe try another battery if you have it. I had a bad connection on my car where the wire plug going into the alt was frayed, down to one wire, it would charge right MOST of the time but then give me problems, it was frayed and a lot of corrosion, just a couple things to check. good luck

 

[72RoadrunnerGTX]

Full fielding a 70’ and up insolated field alternator requires +12v (on the blue wire normally, ign. on ) be applied one field terminal and grounding the other terminal. The regulator varies resistance to ground, to vary field current controlling alternator output. No, functionally it makes no deference which field lead goes to what terminal.

 

[99ss]

Ok had the alt tested and its good. bought a new vlt reg and pigtail .. checked the grounds and the test light is bright where ever I touch the alt, engine , frame, bulkead.. the batt is the only thing of question right now I guess

 

[99ss]

Ok ... NExt question.. how to read multimeter..LOL
really the question is how to check and make sure the needle is accurate...
usng the ohm test if I touch the leads together what should I read.. its a 1 ohm test... should it read 0 for 0 loss or 1 ohm for the amount being put through?.. its reading like there is resistance so my guess is it needs to be 0 for 0 loss...
double check in the internet and found this

Another aspect of using an analogue multimeter for measuring resistance is that the meter needs to be "zero'ed" before making a measurement. This is done by connecting the two probes together so that there is a short circuit, and then using the "zero" control to give full scale deflection on the meter, i.e. zero ohms. Each time the range is changed, the meter needs to be zero'ed as the position may change from one range to the next. The meter needs to be zero'ed because the full scale deflection will change according to aspects such as the state of the battery.

In short.. pardon the pun, my multimeter is out of wack and reading low..... my guess is that I've got 14+ being pushed but was reading lik 8+ due ot the meter not being zeroed... call me stupid !

 

[67 B-body]

Ok ... NExt question.. how to read multimeter..LOL
really the question is how to check and make sure the needle is accurate...
usng the ohm test if I touch the leads together what should I read.. its a 1 ohm test... should it read 0 for 0 loss or 1 ohm for the amount being put through?.. its reading like there is resistance so my guess is it needs to be 0 for 0 loss...
double check in the internet and found this

Another aspect of using an analogue multimeter for measuring resistance is that the meter needs to be "zero'ed" before making a measurement. This is done by connecting the two probes together so that there is a short circuit, and then using the "zero" control to give full scale deflection on the meter, i.e. zero ohms. Each time the range is changed, the meter needs to be zero'ed as the position may change from one range to the next. The meter needs to be zero'ed because the full scale deflection will change according to aspects such as the state of the battery.

In short.. pardon the pun, my multimeter is out of wack and reading low..... my guess is that I've got 14+ being pushed but was reading lik 8+ due ot the meter not being zeroed... call me stupid !

Well, regardless of what it reads,,,,,, you should measure something on the batt posts with the key in the off position. After starting the car, you should read something more than it was when you checked it in step one. If this is true, then I would be inclined to suggest your alt is putting out a charge greater than the batts current state of charge.
If it reads something slightly lower, then I would suggest that your batt is discharging and the charging system is not working. Did you say you tried removing the positive batt cable from the batt post after the car has been started? If so, does the car continue to run?

 

[99ss]

Ok finally got it solved... first of all my multi meter is junk.. time for a new one

thought I had it working but the minute I took the + cable off the car died... so ...
my thought was the exciter wire is not doing its job..as this was the last thing it could be.
I trace it back to the fuse box and low and behold the new painless perf wiring harness mini fuse box holder is the issue... the contacts that hold the fuse werent pushed all the way in so it ( the wire) wasnt getting the current to excited the alt... made sure they were seated all the way and BAM the car runs with the + cable disconnected now... :hello2: