74 dart sport won't charge

-
mjfive

mjfive

Member
Joined
Sep 24, 2010
Messages
13
Reaction score
4
Location
Gosport, IN.
Hello guys. I have a 74 dart sport that I can't get the alt. to charge. I have put everything new on (alt,volt reg,ballast,coil,ign switch,new engine harness, etc...) and still when you start the car the gauge shows it is not charging. When you pull the battery cable off it dies. I saw on here about doing the amp gauge bypass, which I did, still no. If I run a wire from the alt lug over to the battery and start the car, then pull the cable off but leave the jumper wire the car will stay running, but the alt is still not charging. I don't know much about the charge system so any help will be much appreciated. Thanks, Mike
 
Check your connections through the bulkhead connector, they're pretty bad.

Check your connection right at the voltage regulator, often the plug doesn't make a good connection.

Also make sure your voltage regulator is grounded. Run a ground wire back to the engine or battery negative, don't rely on the bolt going into the painted firewall.

What voltage rreading do you get at the battery when its running?
 
I checked all the grounds on the car. took them off cleaned the metal well to make sure they made good contact. even added one from the volt reg to the frame. I think the reading at the battery was 12.5
 
First, NEVER pull a battery cable off a running car. IF the system is charging, this generates a large voltage spike. Also, it does not actually prove anything one way or the other.

I generally think in terms of "sections"

components, alternator, regulator, battery. Remember, "new" does not mean "functional."

output wiring, or "charging line." On a factory car, this involves the above mentioned bulkhead connector, subject to problems, the ammeter, and other wiring weak points

Field wiring.

=============================

WHAT YOU NEED. A multimeter, a 12V test lamp, two or three alligator clip leads, and a side issue, a spark checker, for ignition problems. ALL car owners should have these in their box

A FACTORY service manual, which you can download free, and a wiring diagram of your car, also in the factory manual

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

More here

http://www.mymopar.com/index.php?pid=31

Also there at MyMopar are simplified, sometimes easier to follow non-factory diagrams

========================

WHAT TO DO

Start by making some very simple checks. Turn the key to run. Take your meter and check voltage at the blue field wire on the alternator. Do this withOUT disconnecting the wire. You want it "as normal." Should show "same as battery" voltage.

DISconnect the green wire, in subdued light if possible. You should see a small spark. Take one of your clip leads and connect that alternator terminal to GROUND.

Start and run the engine, bring up RPM easy, and watch the ammeter. It should show a charge. It's a good idea to monitor battery voltage with your meter while doing this, don't allow the voltage to go much above 15--15.5 if you can help it

IF you do NOT see this voltage, leave the key in "run." REcheck voltage on the blue field wire at the alternator, still with the "clip lead" on ground. Should be close to battery voltage.

Clip your meter from ground to the big alternator output stud. Run the engine again, bring up RPM. If voltage stays "low" 12-12.6 or less, it's not charging at all.

If the voltage goes "nuts" that is way high, 18V or so and the ammeter does not show a charge, then there's an "open" in the charging line, most likely the bulkhead connector

Post back with results
 
that model has a white connector in the engine harness about halfway between firewall and alt'. Separate it and check it.
 
Ok just got done unhooking green wire from back of alt and ran it to ground. The amp gauge did show it charging and I slowly brought up the rpms alittle and gauge did show an increase, as did the meter I had on battery. So what does this mean? I'm sorry I'm not smart on this at all.
 
Here is a simplified diagram:

Dual_Field_Alternator_Wiring.jpg


Dont let this all scare you. Here's what you have:

The switched 12V ignition goes to one field terminal, and to the VR "I" (ignition) terminal. The VR case is grounded

On the diagram, 12V is going to the upper (blue) field terminal, and the center "I" terminal.

The green goes from the VR "F" terminal over to the remaining alternator field terminal.

WHAT HAPPENS is that the VR gets power, and this power IS the VR "sense" voltage. It controls "the amount of ground" on the field of the alternator.

So to make the alternator charge "full output" you unhook that green, and ground that field. This causes FULL field current to flow through the field, giving it maximum magnetism.
 
So, what is now left?

What you have proved so far is that the alternator is capable of charging

It is getting 12V field voltage

And the output wire to the battery is probably OK

======================

What to do next?

Very first thing I'd try is dismount the VR, clean (scrape) around the mounting holes and remount using star lock washers. The VR MUST be grounded. MUST

=======================

Next, look over the VR rubber connector. Are the terminals corroded? "Work" the connector on/ off the VR several times, feeling for "tightness" and "working" this helps scrub the terminals clean.

Run it and try again, see if it works

=======================

If it does not, time for more (simple) tests. Please follow exactly. You are trying to determine if the field wiring is OK

Remove the VR connector. With the key in "run" check voltage from the VR harness connector terminals to ground. BOTH should show "same as battery."

Now "rig" a way to jumper across the two terminals in that harness connector. Machine screws are one way.

With the terminals jumpered, this time unhook the BLUE wire at the alternator field, and connect that alternator field terminal to ground.

Again, run the engine, looking for charging.

If it does charge, replace the VR

If it does not, you have a field wiring problem. Post back
 
mjfive said:
So what do I need to do to make the car charge the correct way it is suppose to?
Click to expand...

We are trying to step you through that. That's what testing is for. To determine where the problem lies
 
Well you were right about the VR. I jumped the blue wire like you said and it showed charge. I had another new VR and put it on and it"s working like it should. This blows my mind as this makes the third new one that I have put on to apparently get a good one. First one from AutoZone, next one O"Reileys, now another AutoZone one. wow. Thank you so much 67Dart273 for all your help.Couldn"t have done it without you
 
You are welcome. Here's what MIGHT be happening. You might have an unknown heavy duty alternator, or one with a partial short in the field. In other words, the alternator might be blowing up regulators

To test this, do the following...........

(First what brand and model multimeter do you have? Does it have a heavy amperage scale like, 10, 20A DC?)

Set the multimeter up for high amperage, and disconnect the VR connector. Turn the key to "run." Identify the green wire and hook the multimeter from the green to ground. You are now measuring field current. It should show around 3-4 A If it shows more like 6 or above, then "we" might have a problem

One of the members on here found a better VR that can handle heavy current.
 
I did the test you said and it showed 4-5 on the meter. Do I need to find a better VR than the local auto parts stores?
 
No I think that's OK. If it seems to be charging run one last test. Get the battery charged up and normal, and engine warmed up. At a fast idle or better, the battery should show no lower than 13.5, no higher than 14.5. Optimum is 13.8--14.2.

If that shows OK, turn on the light,s heater, and see if it maintains that at simulated "low cruise" RPM. Don't forget to verify the V belt is properly tight.

Make absolutely certain the VR is grounded, mounted tight
 
Ok, I will try this stuff this weekend and will post results. Again Thanks for all your help.
 
You must log in or register to reply here.
-

Back
Top