I got no response from my last posting. Come on, everyone. Help me out here, please. My 67 Mustang's new alternator is not charging the battery. When I disconnect the negative cable from the battery, the car dies. I just replaced the alternator and the battery. Do these symptoms point to the regulator? The alternator light stays on while the car is running so I took the alternator up to Auto Zone. They said it failed their tests. The new alternator does not seem to fix the problem though as the alternator light still stays on while the car is running and the car dies when I pull the negative cable off the battery. What else could cause these problems besides the regulator? Unfortunately for me when I got this car, the wiring to the alternator was hooked up wrong. The ground was connected to hot and the other wiring to the alternator was connected to ground. I am guessing that the alternator and regulator got fried when the car was started with the wrong wiring setup. Finally, can someone help me with the wiring for my tach? It has a black wire and a red wire coming out of it. Does the black go to ground and the red to the distributer side of the coil? Is there a wire under my dash these should match up to? Thanks again,
Have the alternator tested, buy a new regulator, and get a repair manual that shows the correct wiring. Do not trust the colors, trace everything to be sure you have it right. Nothing beats having a manual with pictures (schematics) in front of you.
You probably fried the regulator, and now it, in turn, is frying the alternator. Your best bet at this point in time is to find an electrical shop that can truly diagnose the problem(s). Running reverse polarity on charging systems is not good.
As for your tach, it goes in-line between your ignition switch and the coil. There should be a bullet connector between a "pink" thick resistor wire and a red w/green stripe wire. Pull it apart and plug the male lead from the tach into the female lead and vice-versa.
'Electrical Guru: Let me Check Your Shorts! Ooops...that didn't turn out right.
I fought this problem just before Knotts, went through 4 alternators, 2 voltage regulators and one battery. ok, with a tach equipped car, the alternator harness is the "tach version" and not the standard alternator harness. The tach version has a plug leading off of it, midway up to the starter solenoid. This pigtail and plug connects to a plug on the harness coming from under the dash and going to the solenoid. This is the feed the pulls voltage off the ignition switch to excite, or turn on, the alternator. It is also the connector which allows juice from the alternator to feed back into the battery, through the 10 gauge black wire which connects to the forward thick post on the solenoid.
Before you do anything else, I recommend that you check your alternator wiring harness and make sure a) it is the correct one for a tach equipped car(factory tach!); and b), the connector is not fried in the wiring harness. My problem was solved with two new bullet connectors. After that, the alternator which autozone said was no good, ran fine and is now charging the car with 14.5 volts. I think the autozone counter help does not know how to test the old style alternators that have the external voltage regulator. I think they set up the machine for the internallly regulated alternators and when the machine does not find the voltage regulator circuit in the alternator, it fails the alternator.
If you check some of my posts on this about 3 weeks ago, there might be additional helpful details for you.
Rebuilding a classic mustang is a reality check on your individual state of perfection.
I would like to add that Advanced Auto did not check mine correctly either...After some trouble shooting on my own, I found that the "STA" terminal is UNUSED in a non-tach equiped car. In a Tach car, the "STA" terminal is used in the "alternator idiot light" circuit by running to the voltage regulator. In either case, that terminal is NOT used in the actual charging circuit for testing. Only the "BAT", "GRND", and "FLD" terminals are used. "BAT" should be the Black w/red stripe, "GRND" should be the Black wire, and "FLD" should be the White wire. Advanced Auto was hooking up the white wire to the Stator or "STA" position and told me my alternator was bad. Only after I bought a new one and found it also wasn't charging did I perform some tests myself and solved the problem by removing the white wire from the "STA" terminal and moving it to the "FLD" terminal and viola...I started getting 14 1/2 volts to the battery...Let me know if this helps... Also, if you are ADDING a tach then perform a search using my user I.D. back about 2 months and you'll see my post on how I hooked up my tach without the factory wiring installed.
Thank you all for your responses. I especially liked Carpul Tunnels response. I do not think I have the wiring harness with the black wire that feeds back to the battery but I will print out these responses and check over the wiring again. I thought the only black wire from my alternator was connected to ground as I believe mine now is. There are three other wires coming out of the alternator on a module like setup with flat-round terminals to connect to the alternator. One of the three is larger. I got some wiring diagrams online so I will have to go back to reviewing those as well. Eitherway, I sure appreciate the comments and will keep posting to report progress, or lack thereof. I will be out of town for about a week so the project stops again for awhile.
It turned out the voltage regulator was not sending the current back to the battery. It must have been fried when I initally tried to start the car without looking to see that everything was connected correctly. Now the battery is being charged properly. The alt light does not stay on when the car is running. I am very happy. All I have left to do now is connect the tach and radio so I can close up the dash. I have just two wires coming out of the indash tach, a black and a red. I am guessing the other wires for the tach are part of the instrument cluster itself. Thanks again to all who voiced their opinions. It really helped.
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