I have a problem with the charging system in my 66 coupe.

I bought a lighter socket volt meter from Auto Zone to monitor my progress and troubles. The meter reads barely over 12 volts, never 13 or 14.

I have replaced the alternator twice, the battery, the voltage regulator twice, and the entire wiring harness under the hood. I have also replaced the heater blower motor switch.

I saw a suggestion that crossing the F and A wires (I think that is what they are called) on the VR harness would spike the voltage to full-output of the alternator and if I got 14+ volts, the alternator was good. I did get 14 volts and I think it shot all the way to 16.

What else could be the problem. I am now looking into a 1-wire alternator solution to try and solve this problem, but if there's something else I can try, I will hold off on the upgrade.

Thanks

 

wait so your problem is the meter is reading 12 when you are looking for 14-16?[&:]

the battery is a 12v battery in case you didnt know. if it reads 12, then you're good to go man.

 

Thanks for the reply.

When I plug the volt meter into my other two cars, I get a ~12 volt reading when the engine is off and 13-14 volts when the engine is running.

While driving the pony, pressing on the brakes causes the meter to dip into low 11 volt territory. Taking my foot off of the brakes causes it to go back to low 12 volt range.

Additionally, the alternator has a post for the stator, I assume (it is marked with an S). I don't have any wire connected to this post. Is that supposed to not be connected to anything?

 

Here is a good thread for updating to an excellent alternator:
https://mustangforums.com/m_3361254/tm.htm

We are fortunate to have a very good FAQ section "stickied" to the top of the forum page. Lot's of really great stuff! I'd highly recommend perusing this as you have time.

Make sure to check the ground path. Heavy paint on brackets and engine block can cause this problem. Also if you are missing the ground strap between the engine and body of the car, or if there is not a clean metal to metal contact of this ground strap, it can also cause your problem.

Fully charged static voltage should be 12.6V. While running a properly operating system should be between 13.6V and 14.8V. 12V static is considered dead.
I'd recommend a quality volt meter to do your inspections, rather than using the cigarette lighter circuit. I'd also recommend charging and testing the battery, before proceeding.
Good luck,

 

My alternator is grounded (along with the negative battery post) to a bolt into the side of the engine. I assume it is the engine mount because the bracket goes from the engine to the frame where the shock is.

Is this the appropriate place for the alternator and batter to be grounded to?

 

Check your grounds. if you have replaced everything, and it still doesnt work, you could have problems getting a good ground. in fact, I would just check all the connections to be sure.

 

I added a new ground wire from the engine mount bolt (where the negative battery post and alternator harness ground to) to various places under the hood to no avail. Not sure if I mentioned before but my wiring under the hood is all new.

I found another suggestion to jumper the A and S terminals on the VR (while the VR is connected). All this did was keep the radio and accessories on while the keys were out of the ignition. There was no change to the charging system.

I am at a loss as to what I need to look at next.

 

Update:

I took the car to Auto Zone. They hooked up the big tester machine and found that the alternator was good, the VR was good, but they swapped out the battery. I am not sure if it is because the battery was bad or if it was just really low because of the lack of charging.

I talked to my brother-in-law and he suggested there might be some ground issue inside the car. I took out the stereo completely but noticed the volt meter in the lighter socket was still showing ~11 volts when the lights and heater fan were going.

I decided to hook the little meter up under the hood and saw that I was getting ~12.5 with the headlights/blower motor on.

I assume that this is an acceptable level for keeping the battery charged, am I correct?

As a side note, it seems like something inside the car is preventing me from getting full voltage and power to the lighter socket. It is possible that it is using the incorrect wiring.

 

If you have a DVOM (Digital Volt-Ohm meter), try the following checks:
(Note: if you don't have a 20VDC scale, use the lowest scale that will read up to 15V).

1). VOM set to read 20VDC scale; Negative cable disconnected from the battery. Positive meter lead on positive battery post, negative meter lead on negative battery post, what is the voltage:

2). Ignition off, doors closed, clock and any other drain disconnected. VOM set to read amperage 20A scale; Positive meter lead attached to negative battery cable (that is still disconnected from step one) Negative meter lead connected to negative battery post, what is the amperage:

3). Negative cable connected, car running at idle, no accessories on. VOM set to 20VDC scale. Positive meter lead on positive battery post, negative on negative battery post. What is the voltage reading:

4). Same as #3 except raise rpm to above 1,500 rpm. What is Voltage:

5). Same as #3 except turn on headlights. What is voltage:

6). Same as #5 except raise RPMs to above 1,500 rpm. What is Voltage:

7). Headlights on, car running above 1,500 rpm.VOM set 20VDC scale. Negative meter lead on Battery positive post, positive meter lead on "Batt" terminal of alternator (Big wire). What is the voltage:

8). Headlights on, car running above 1,500 rpm. VOM set to 20VDC. Positive meter lead on case of alternator, Negative meter lead on negative battey terminal. What is voltage:

9). Coil disconnected, cranking engine. VOM set to 20VDC scale. Positive meter lead on positive battery post, negativemeter lead onnegative battery post. While cranking the engine what is the voltage:

10). Same as #9 except; Positive meter lead on positive battery post, negative lead on main cable lug of starter. What is the voltage:

11). Same as #9except Negative meter lead on negative battery post, positive meter lead on starter case. What is voltage:

These are some home-cheesy checks that will give you an idea of charging system output, voltage drain on the system, and voltage drops on the power cables. The key to diagnosing a charging or starting system complaint is to start with a known good and fully charged battery. Ensure, the meter leads are touching clean metal (or lead). #7, #8, #10, #11 are looking for poor connections or cables. We don't want to see anything more than 0.2V during these tests (I normally don't get excited until it's morethan afull volt).

Test #2 is lookingfor a drain on your system that would over time kill the vehicle. With allaccessories off, theclock disconnected and the main power lead to the radio disconnected, you shouldn't have more than 0.5A (Normally on old muscle cars this will be less than 0.2A).A 0.5A draw will kill the battery in about a month, depending on ambient conditions, and state of battery.

Test#1 should be between 12.4 and 12.6V. Test#3 should begreater than 12.6 (preferably around 13V or better, but will vary depending on state of battery charge, which is why I like to have a fully charged known good and tested battery). Test #4 should increase in voltage again. I like to see somewhere between 13.6V and 14.5V.
Test #5 I want no less than 12.6V. In fact I turn on all accessories wipers, heater, radio, curling iron , etc, and I still don't want to see below 12.6V. Test #6, better darned well be higher voltage than #5, and should be in the 13.6-14.5V range.

If you can do these tests,and need help interpreting your results, post what you get, and we can help solveyour problem.
Good luck,

 

Scott,

Thanks for the step-by-step. My multimeter shows everything in decimal values. I assume that they are a percentage of the 20 VDC value I selected on the meter. Here are my results.

1. .84
2. .05 (not sure what's drawing that power as I removed the stereo completely from the car)
3. .83
4. .83
5. .82
6. .82
7. .81 - .82
8. .83

I didn't go past #8 because I am not having problems with the car starting, unless the battery is completely drained.

I am also wondering if there is a wire hooked up incorrectly on the engine harness. When I replaced it, I unplugged the old harness and plugged in the new harness one connector at a time so I would not get mixed up...but that's not to say that it was correct when I got it.

Again, thanks for the help Scott.