Alt volts

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Otateral

Otateral

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What's the normal range for volts coming from the alternator? I'm getting ready to do the MAD amp gauge bypass and want to make sure I'm not going to have any problems and end up frying the fusible link. I tested 15.1 volts at idle directly at the alternator and 13.5 volts at the battery. Just curious if I do the mod, will I have too much voltage?
 
I have used a voltmeter (plugs into cigarette lighter) in several cars. It usually reads 14.5 V with the engine running and 12.6 V with the engine off. I think that is typical. Others are more expert, but I think the MAD bypass will make your alternator output voltage a bit less since less drop in the wiring and ammeter.
 
The fact that you have that much more at the alternator SHOWS that your harness has a problem

If you look at the simplified diagram in the MAD article, and follow the path from the alternator to the battery, you have several points there that can cause voltage drop

First and foremost are the two associated terminals in the bulkhead connector, IE where the battery feeds into the interior and to the ammeter, and where the alternator feeds into the interior and to the ammeter

Then, you may have a problem with the ammeter itself, corrosion/ loose inside where the studs "sandwich" together to contact the guts of the meter.

All this adds up, and the wiring isn't all that big to begin with, so with heavy charging, IE low battery, even the wire can add a little bit.

The short answer is, your bypass should improve things.

"Optimum" for a warm system (the regulator is temp sensitive) is close to somewhere around 13.8--14.2. This can go up or down with temperature, but much below 13.5 is a problem, and much above 14.5 is a problem.
 
You may want to conduct a voltage drop study before attempting the Mad bypass, and correct the poor connections and conductors causing excessive voltage drop.

Most important, and one of the most common points of voltage drop is at battery terminals, and ground connections to block and head to fire wall. These connections need to be freshly remade before the following tests are performed. Often a ½ volt or more can be scrubbed from the system with these connections.


Voltage drop can be checked by placing one probe of volt meter on negative battery terminal, and the other on case or frame of voltage regulator, alternator, and spark controller if you have electronic ignition. The optimal reading is zero, 0.1 -0.2V is max drop allowed with ignition key on. The fix for this would be to run a ground loop of #12 gage conductor to one all three devices mounting screws, and back to battery negative terminal. To test under dash make up a jumper that connects to neg. battery post long enough to reach the dash area. This will insure a good ground with no drop to work from.

Next test the voltage difference between negative battery terminal, and all connections of charging circuit as above, but second probe to be landed on each brass connection in that circuit with engine running. This includes ignition switch connections, both sides of bulkhead connector for big brown, big red, and big black wire, as well. Anything that adds up to 0.2v difference is unacceptable and needs to be repaired with new connections, or carefully cleaned to remove excess resistance in the circuit.

So what I’m saying hypothetically is, as you test from battery to engine side of bulkhead connector finding 0.1 volt drop, than the dash side of bulk head connector same wire find an additional 0.2v drop, at ignition switch in and out 0.1v drop, and back out through the connector finding 0.2 drop, those drops are added giving 0.6v drop; too much it is ½ volt high. These tests have to be made at each of the connections in the charging circuit including voltage regulator, ballast resistor, field wire etc. Performing connection to connection readings show where a problem exists, readings between battery and the far end of charging circuit will show total drop, but not which points it is coming from.

Most important, and one of the most common points of voltage drop is at battery terminals, and ground connections to block and head to fire wall.

A half volt of drop read by voltage regulator will cause alternator to increase voltage by one half volt.

I performed the mad bypass after repairing any voltage drop problems, and used the treaded stud on starter rely as voltage sensing point which allowed the charging voltage to become normal. Before this conversion, and voltage drop elimination, my charge voltage was 15.5 volts, which would boil the battery during a long trip.
This testing and repair takes a lot of time, but having electrical system working properly, and reliable is priceless.
 
Also keep in mind that voltage will not kill the fusible link, amperage will. If you have that much drop, you have high resistance in your charging circuit. Clean all the connections well. Things will work better.
 
Great to know, Chief. One other question... how necessary is it to put in a voltage gauge? I realize that when I do the bypass, the altmeter won't be hooked up to anything. Could I get by without any electrical reading for another 8 months or so? At that point, my plan is to put in an aftermarket wiring harness and gauges. Just don't want to clutter up the dash too much with extra gauges in the meantime.
 
i went and bought a $12 volt gauge from oriellys after the bypass just to be sure im never overcharging
 
If you never had it, you'd never miss it. Nice thing about volt gauges is they can be mounted anywhere, and only require 2 small wires. Cut the hole in the back of your glovebox. Want to check volts, open the door. Close the door, and what voltmeter.

Aftermarket wiring harness and gauges? To each their own, but that seems a mighty big wheel to reinvent.
 
Otateral said:
Great to know, Chief. One other question... how necessary is it to put in a voltage gauge? I realize that when I do the bypass, the altmeter won't be hooked up to anything. Could I get by without any electrical reading for another 8 months or so? At that point, my plan is to put in an aftermarket wiring harness and gauges. Just don't want to clutter up the dash too much with extra gauges in the meantime.
Click to expand...

Check out this thread. I did the mod for the 67 style dash in mine, and love it. The cheap (20 dollar) Sunpro gauge has an ajustment pot inside, so you can set 14V to be exactly at the middle of the old ammeter scale.

Read the whole thread, it covers a lot of ground

http://www.forabodiesonly.com/mopar/showthread.php?t=119480&highlight=ammeter+conversion
 
Got it done today. Only hiccup is now my temp gauge isn't working so will have to trace that down. The condition of the wiring was pretty bad and burned through in a few spots.

Good news is no drop in volts at the battery, and the hum is gone from the speakers.
 
Ok so carrying over from the other thread, this is todays measurements...

Alternator (car running at idle) 15.1 volts

Bottom of VR (engine off, key in run) 10.9 volts

Then checked bottom of VR and positive side of battery: 1.1 volts

This tells me that I probably have a bad connection somewhere along the line. The bulkhead connectors are all pretty bad. Saw that when I did the MAD bypass. I will troubleshoot this further and check the rest of the connections.
 
One other thing. I jumpered the positive battery to the bottom of VR and then tested the alternator again, in run position and got 14.5 volts. Am I correct in thinking this confirms that the VR is working?
 
Yes. You have a drop problem in the ignition supply path Your most likely suspect is where the dark blue run passes through the bulkhead, and from there the ignition switch connector, the switch itself, and in rare cases, failure of the welded splice in the harness, which is a few inches "in" (taped up) connected to the black ammeter wire.

One way to "fix" it is to use a good quality relay, supplied power from the starter relay stud, to run ignition/ regulator.

The reason the charging voltage dropped when you bypassed power directly to the regulator is that the regulator is now more truely sensing battery voltage.
 
update: took out the cluster today to get more room and noticed that the black wire that originally went to the ammeter has melted through about 6 inches of wire. Easily could have had a fire here. I didn't notice it when I did the bypass, because its tucked away near the top of the dash. Could this also have something to do with the loss in voltage?

More readings:

After cleaning the engine side of the bulkhead, I've got 11.5 volts at the dark blue wire that feeds the voltage regulator.

12.2 volts at the ignition switch, going in through the red and coming out of the dark blue. So the switch is good.

The wiring diagram shows another splice between ignition and the bulkhead which feeds the oil/brake indicator lights. I will see if I can track down that splice and see if I can repair that .7 volt loss.

Is 12.2 volts at the ignition switch a decent amount or do I need to troubleshoot that further as well?

My plan is still to go to an aftermarket wiring harness next spring. I wonder if I'm making too much work out of something small and if I should wait until spring and leave things as they are. Since jumpering the starter relay and voltage regulator will provide good voltage, should I just put down 14gauge wire there and leave it be for the next few months?
 
You need to compare it to the battery. That's why I'm always preaching "voltage drop." You can do this the hard way or the easy way. In both cases you must measure under a LOAD to cause the drop to show up.

In the case of the dark blue, the charging system regulator circuit, and the ignition system and what little else is on that dark blue causes the load

HARD WAY:

A Carefully measure and NOTE battery voltage, IE 12.2, whatever

B Measure the different points along the harness that you suspect a problem, and note against battery reading

EASY WAY

A Clip one meter lead to battery POSITIVE post, with an extended clip lead or wire if necessary

B Now hook the remaining meter lead to the various points on the harness and directly read the drop. When the drop starts to get LESS, you know you've gone "past" the trouble area.

You mentioned the black ammeter wire. You should inspect that further. Untape the harness as necessary (probably about a foot) starting with the black ammeter wire. Sooner or later you'll reach a great big factory splice. Make SURE that splice is not broken before you tape it back up. Then can, have, do, fail.

What it all comes down to is

with everything "normalized" IE "ready to run

with key in "run" engine off

You want NO MORE than about .3 (three tenths) volt drop at the regulator terminal compared to battery.

So once again, with one meter lead on battery positive, remaining lead on regulator IGN terminal, you don't want to see more than .3V
 
That makes a lot of sense. I appreciate the help here. Everyday I'm learning more and more about this stuff.

About my last question, would running a wire between the starter relay stud and the voltage regulator work as a temporary solution? I imagine it may put a drain on the battery when the engine is off. But it could help in at least avoiding a cooked battery while driving.
 
No, it would probably cause LOWER voltage in the system. As it is now the regulator "feels" the drop and increases output accordingly. If you move the point of voltage sensing upstream of the problem, the regulator will no longer raise alternator output to compensate. Heck, you could connect the voltage regulator directly to the output post on the alternator. Then the regulator would directly regulate the alternator and the alternator only. You'd have a very constant alternator output, but it could not compensate for anything downstream. This would effectively be like a GM 1-wire setup, which work well for very simple systems like tractors, boats and hot rods, but not on something as complex as a 1960's car.

If your battery is cooking it is because the alternator is having to overload the primary charging circuit to create adequate voltage downstream. If the plumbing is clogged running the pump harder won't help.
 
Isn't that what I want, though? Right now, the alternator is overcompensating and overcharging the system because of a bad voltage reading. A direct line from the battery would seem to solve that, and bring the alternator down to 14.5 volts. Then if the battery is low, the VR would sense this and increase output.

At least, that's my (limited) understanding.
 
No, at best you'd be treating a symptom and not the root cause. As you describe it, your charging system is in terrible condition. If you think that second guessing the staff of engineers that designed the wiring will provide a viable work around for what is an apparent defect, well, be my guest. You'll either end up with a dead battery, or a fire which will lead you directly to the problem that was already there.

Something is wrong with YOUR car, not the design. Find the problem. The parts it left the factory with worked then, and will work now if in reasonable condition. I know the "bright shiny object" approach is definitely a draw, especially if you can buy a chromed overpriced version of the perfectly functioning part you have now from Summit. It's your money.
 
I definitely understand what you're saying. I'm just trying to avoid having to do the same job twice. Once now, then once again in 6 months or so when I redo all the wiring.
 
You don't need to re-invent the wheel. Either fix the wiring problem or "fix" it so the wiring problem "does not matter."

One way to do the second part is to buy a quality Bosch style relay and mounting socket.

Get contacts power for the relay from the starter relay, through a nice big fuse, say, 20A in a quality fuse holder

Hook the other contact to power the stuff in the engine bay that get power from the dark blue IGN run wire, IE break that wire

Then use the end coming from the bulkhead connector to fire the relay.
 
Okay, did some reading to find out just what a relay was. (More knowledge, yay!) Is this the sort of thing I could setup?

I still will likely try and hunt down where the voltage drop is, but it's good to know that I have other options. I have a feeling that I'm just losing .1 volts here, .2 volts there, for a cumulative drop. Rather than a big drop because of 1 bad connection, I think I have 3 or 4 that together add up to 1volt. Hence the reason for the rewire in the spring when funds allow it. Until then, I just want the car to be drivable.
 

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Before you change anything you should hunt down the voltage drops. This MUST be your #1 priority. Once you do that, the problem will go away you'll need to do nothing further. As for re-wiring the car, why? If your factory wiring is in that bad shape, by all means get new (or reproduction) FACTORY wiring. If you were thinking about some sort of "universal" "EZ" or "hot rod" one size doesn't fit all harness, skip it. If you think you have trouble now, imagine what it will be like with a crimp connector on the end of most every wire.
 
Ok, so replaced a lot of connections at the problem areas. Now, I've got .6v loss at the ignition side of the voltage regulator. But if I unplug the IGN wire from the ballast resistor (see attached photo) I've got .3v loss only. Could this mean a bad ballast resistor or ground? If I can take care of that, I will be at only .3v loss in voltage between the voltage regulator and the battery.

I plugged the ballast resistor back in and turned the car on. I see 14.4v at the battery.
 

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No the reason you have less loss is that you have removed some of the LOAD. That is the way that you check voltage drop. You have a simple circuit picture in your mind not necessarily "current flow" but rather "function"

Power starts at the battery. In order to get to the ignition and regulator it follows this path:

Battery -- fuse link -- bulkhead connector -- ammeter -- to the welded harness splice -- to ignition switch connector -- through the switch -- back out the switch (ignition run/ dark blue) -- back out the switch connector -- back out the bulkhead -- to the

ignition system (ballast resistor)

regulator IGN terminal

on newer (70/ later) vehicles it also feeds

alternator field (blue)

some smog doo dads if used

electric choke if used

So on your car when you turn on the key, that dark blue sees a LOAD. That LOAD is the field current of the alternator through the regulator and...........

The ignition system through the ballast. On cars with breaker points distributors, the points must be closed. On Mopar ECU systems, whenever key is on, the ignition draws power

So........................

If you are measuring the drop in that circuit

and you unhook the ballast, the drop will be less because there is less load

IF you were to unhook the regulator, the drop would be zero or nearly zero, because the only load on that wire would be the gauges, oil warning lamp, and your meter, which draws very little current.

Also, if the drop is in the bulkhead connector, what the gauges and warning lamp(s) draw will not show up as they don't go through the bulkhead.
 
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