Current (no pun intended) consensus on 1965 ammeters/wiring

[BKCowGod]

My '65 Dart has come a long way. I have added the following:

• Mopar electric ignition
• Solid state voltage regulator
• A relatively small stereo (10 amps)
• H4 headlights (9 amps)
• Electric fan (8 amps)
• Volt gauge wired directly to battery

Additionally it has a very old underdash A/C rated for probably 7,000 amps judging by the noise.

The stereo is wired directly to the battery, the headlights and fan are wired to the battery through relays. The alternator it came with appears to be original, or salvaged from the Edmund Fitzgerald some time ago, and it has been showing some significant voltage drop even with only the stereo on. At idle I have been around 12.5, rarely above 13. Today I had to turn off the a/c and the electric fan because even at cruise it was dropping below 12 on the gauge.

Stopped by O'Reilly's and picked up one of the remans rated at 55a. I know the remans are crap, but for the ability to test the component and have a good return policy and instant gratification it's hard to beat.

With the new alt, it is idling right at "C" on the ammeter and a hair above 13v with only the stereo. Revving the engine moves me 1/4" above C and moves the volt meter up to 14 or so. I felt all relevant wires. Warm but not hot, but I also didn't drive it on the freeway for an extended period of time and the battery was probably somewhat discharged as a result of the above described voltage drops.

That was really long winded, but there are so many posts about ammeters that contradict each other that I wanted to provide as much data as possible about my setup.

Now....

1) I wish to keep the ammeter for now (mainly because I don't want to remove the cluster again). How long until I catch on fire? I know the '65 had magic wiring, but how magic is it?
2) Can I run a nice thick wire from the alternator to the positive terminal on the starter motor and make everything better? Will the ammeter still do anything if I do this?
3) I do have a spare bottle of Lucas smoke from my Land Rovers and my MG - is it compatible?

 

[67Dart273]

We just had a similar thread on an early girl
1...Start by reading the MAD article which, if you do not do this procedure, gives a good overview of the why and how of this/ these failures
Catalog

2....If you use a bypass wire as you mentioned, you MUST fuse it as there is no other protection. I'd use oversize wire, at least no8 or no6. Crackedback on here sells a nice kit

3..If you do the wire bypass you STILL need to have the bulkhead connector in good shape as the two wires (red and black) now become parallel feeds into the interior for all the loads in the vehicle, except the starter. Connect the red/ black ammeter wires together, but also make sure the eyelet ends are in good shape, or cut them off and splice the wires, or replace the eyelets, then bolt together.

DISCONNECT the battery when doing all this!!

 

[67Dart273]

The last issue which affects charging voltages---assuming the regulator/ alternator are OK and that the regulator is at the right setpoint...........is the actual voltage which the VR SEES AKA "voltage drop". This is a common issue

To check this, Turn the ignition to "run" with engine stopped. Stab one probe of your meter into the top of the battery POS post, and connect the remaining one to the VR IGN terminal. You are hoping for a very low reading, the lower the better. More than about .3V (3/10 of one volt) you need to look into it

Also check the ground circuit. To do that get the engine running on "fast idle" and do this check with all accessories off, and again with all of them on, headlights, radio, heater, whatever

Stab one probe into the top of the battery NEG post, an the other into the VR mounting flange. Again, the lower voltage reading the better, and zero is perfect

 

[RustyRatRod]

7,000 amps. That's a lot.

 

[Mattax]

3) I do have a spare bottle of Lucas smoke from my Land Rovers and my MG - is it compatible?

Absolutely. The systems are very similar. In fact one day my coworker borrowed a coil from our test Jaguar XJ as a temporary replacement for his '66 Fury.

That was really long winded, but there are so many posts about ammeters that contradict each other that I wanted to provide as much data as possible about my setup.

Thank you!!! Yes very helpful to have all the info.

1) I wish to keep the ammeter for now (mainly because I don't want to remove the cluster again). How long until I catch on fire? I know the '65 had magic wiring, but how magic is it?

Sadly they are not magic and we've seen examples where those fail too.
Their big advantage is the large contact surface of the connectors for the power supplies. The ring terminals screwed to the flat terminal are generally going to have more positive (pun) contact than 1/4" push on terminal. That doesn't mean they are immune to overloading and overheating.

2) Can I run a nice thick wire from the alternator to the positive terminal on the starter motor and make everything better? Will the ammeter still do anything if I do this?

You can. However probably better off running the wire directly to the battery or the starter relay (away from heat). Install a fusible link or maxifuse on the line, so there is still some protection against battery shorting.

Will the ammeter stiull do anything? Yes. whenever the shorter/easier path for current flow is through that wire, the needle will react. MoparTim observed it will still move to discharge during starting. But what you are doing is a little different, and depending on the wire lengths and quality of connections, you'll find out what happens in your setup.

At idle I have been around 12.5, rarely above 13. Today I had to turn off the a/c and the electric fan because even at cruise it was dropping below 12 on the gauge.

With the new alt, it is idling right at "C" on the ammeter and a hair above 13v with only the stereo. Revving the engine moves me 1/4" above C and moves the volt meter up to 14 or so.

Here's the deal:
Stereo plus Fan plus Battery recharging, in addition to ignition and field.

Recharging the battery is a big variable. Immediately after start, its going to draw a lot of current, or try to. The more its disharged, the more it will want to draw for recharge. It will also draw more current when the power supply is at a higher voltage. In that respect it acts like other devices. I'm sure you've seen the headlights are brighter when running on alternator power (14 Volts more or less) than battery power (12.5 Volts more or less).

So here's the issues with your current wiring strategy.

The stereo is wired directly to the battery, the headlights and fan are wired to the battery through relays.

Even though ypou've wired these to the battery, when the engine is running the power supply is supposed to be the alternator. After all, its offering power at 14 Volts not a measly 12 Volts.
Power is going to have to flow from the alternator to the battery to power any of those devices. So now the ammeter is showing current to recharge the battery plus current to run the devices. That power also has to go through a bunch of connections and a fusible link.

A relatively small stereo (10 amps)

That's still more power than typical stock or I'd suggest using the fuse box.
If you will be using hte stero with the engine off, this will further drain the battery. In which case, you may want to rethink recharging through the factory ammeter and use a direct wire like you asked about. Select a battery that can handle that type deep discharge and potential high rate of charge.

Electric fan (8 amps)

The easy solution is use a factory and put a shroud on the radiator.

H4 headlights (9 amps)

The problem here is the factory wires where just OK for the 6012 lamps. Using relay is great, but power it directly from the alternator. Install fuse or circuit breaker.

Volt gauge wired directly to battery

This will likely cause a very slow drain.

Additionally it has a very old underdash A/C rated for probably 7,000 amps judging by the noise.

LOL Under dash A/C on my '67 contributed to excessive heat and some damage (hardening) of the insulation on the factory accessory termination on the ignition switch.

I think the MAD article is confusing, and somewhat misleading but if it helps you, great.


Diagram showing current flow from an alternator with direct wire to the battery for recharging. Orange arrows represent current flow.
Notice the ammeter does not detect current for battery charging.

 

[BKCowGod]

Absolutely. The systems are very similar. In fact one day my coworker borrowed a coil from our test Jaguar XJ as a temporary replacement for his '66 Fury.

Awesome insights, thanks! So is my current setup "you should not drive that", "watch for smoke", or "it might be fine for a bit"?

 

[Mattax]

Well this is for older models.

On your '65 Dart the harness smoke will be negative earth.

Revving the engine moves me 1/4" above C and moves the volt meter up to 14 or so. I felt all relevant wires. Warm but not hot, but I also didn't drive it on the freeway for an extended period of time and the battery was probably somewhat discharged as a result of the above described voltage drops.

Well personally I don't like any wire getting warmer than ambiant.

Increasing the alternator rpm above slow idle increases its capacity. Somewhere between 1250 and 2000 engine rpm the alternator's capacity will be near its maximum potential.
The ammeter is scaled 40 amps charge to 40 amps discharge.
If the needle is halfway between center and C, then about 20 amps is going to the battery...
Or in your current setup, to the battery, fan, stereo, and headlights.

If the needle is pointing 1/4" past the C, then its over 40 amps.
I consider anything close to 40 amps as dangerous territory. The longer and more frequently the wires and connections see that much current, the more heat generated by resistance. It becomes a downhill spiral.

Also letting a battery draw 30 amps for a long period of time is going to heat the acid. This can be destructive as well. Even 20 amps for 15 minutes or so can really heat up an AGM.

 

[cudamark]

I'd start by charging the battery fully and then see where the reading is on the ammeter. I don't see that you've added much of a load on a stock system. The headlights and fan are pretty much a non-issue since they're wired separately and don't pull significant juice through the bulkhead connector. I'd probably do the same with the stereo and call it a day.

 

[Mattax]

The headlights and fan are pretty much a non-issue since they're wired separately and don't pull significant juice through the bulkhead connector. I'd probably do the same with the stereo and call it a day.

They are currently wired to the battery, so they pull juice through both bulkhead connectors and the fusible link when the alternator is working.
In my illustration I show it them connected to the alternator and a direct wire to the battery since that's what he began by asking about.

 

[cudamark]

The '65 bulkhead connector doesn't have the same alternator/battery connection problems that the later male/female plugs have. What little extra charging amperage needed to work those add-ons won't be an issue if his battery is in good shape.

 

[Mattax]

On a factory system, most of the time there is no current flowing through the wire from the main splice to the battery.

(Not illustrating with arrows the current returning via ground to the power supply, but of course it does.)

Same factory system, but now supplying 10 amps to the battery.

With a 10 amp electric fan attached connected at the battery, the same route is taken:

Now lets turn on the fan immediately after start while the battery is still recharging.

Now there is 20 amps through all of those connectors and the fusible link, and 25 amps through the R6 line and connector.

Continue adding to the maximum load expected by turning on the headlights (+9 amps), and cranking up the stereo (+5 to 10 amps).
This is same type of load as can happen with recharging a very low battery from the alternator while driving on the highway.

This can happen

Pics from this thread Anyone Know What this Connector is Called?

So can you let the magic smoke out? Yes you can.
Whether its the 16 gage fusible link or other weak points that it escapes from - that will depend on which has a the highest resistance to flow and the least ability to dispose of heat. Could it survive for 5 minutes? Sure. Can it survive for 20 minutes at 20 amp? probably, but maybe damaged. Can it survive 40 amps for 20 minutes? Wouldn't bet on it.

Running the stereo through a connector at the battery may get cleaner power. if that's needed, then do it. Just know that's a load you may want to keep off the line while the battery is still charging. But the headlights and fan, if they are going to be attached on the battery side of the ammeter, then at minimum the direct wire is needed.

 

[BKCowGod]

Thank you to Mattax and Cudamark - loving the detailed and factual discussion.

I happened to have a nice unused 2 gauge cable and a 60a breaker from an earlier iteration of my squarebody's electrical system. Ran that from the alternator to the battery positive. Rendered the ammeter useless, it stays pointing straight up and down. Now the battery is showing rock solid 15.5 volts at idle (verified against a meter touched straight to the pos/neg of the battery) with no fluctuation at cruising speed. A bit higher than I would like, but better than 11. Turning on the lights or the cooling fan drops me down to 13-14 at idle.

One thing I noticed was a loose field connector on the old alternator. Might have been the cause of my issues, but not sure I really want to put the old one back in at this point. No matter what if I am running all accessories I will be exceeding the rated output of the original.

 

[Mattax]

Now the battery is showing rock solid 15.5 volts at idle (verified against a meter touched straight to the pos/neg of the battery)

Measure voltage drop between the alternator output and the voltage regulator's input or 'sense' terminal. If there is, then work back along the current path to the regulator until you find the cause. If there isn't much voltage drop on the feed, then check for voltage difference in grounding.