'68 Barracuda - charging system questions

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Dave NEO

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checked grounds, all good - will finish full charge of battery -check voltage at VR blue wire.
 
Battery charged to about 12.5. Started up and shows 8V at blue wire. Just the 12.5 showing on battery terminal. Alt BAT stud still pegging needle at 16V+. WIll put in the ammeter bypass wire and see what changes...
 
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with bypass wire in place the alt BAT stud is showing 13.8, the blue wire on VR is about 5V at idle and decreases with higher RPMs. I get headlights/dashlights flickering at idle which disappears with increased RPMs. (I have crackedback's headlight relays in place BTW). Anyway I can live with this but think I will need to watch overcharging battery..art least want to run it until it reaches full battery charge and see if charging current gets knocked by VR buty 13.8 is probably good if I remember correctly.. comments appreciated. thnx
 
Battery charged to about 12.5. Started up and shows 8V at blue wire. Just the 12.5 showing on battery terminal. Alt BAT stud still pegging needle at 16V+. WIll put in the ammeter bypass wire and see what changes...
My advice is:
(a)look at the ammeter and see what it shows you.
(b) Backprobe the bulkhead connector on both sides of the alternator feed.
(c) check the voltage at the bulkehad ignition wire cavity.

Based on what you've found the ammeter is not likely involved in the problems. So based on the information so far, bypassing it at the meter will simply remove a usefull tool
Bypassing the ammeter on the engine compartment side can increase the current trying to get through the existing problem spots.

This diagram is pretty close to your '68 Barracuda.
Ignition wire's may or may not have the white stripe, and the power feed to the key switch may red.
upload_2019-4-17_8-37-50-png-png.png
 
As said before, there are two things going on here.
Somewhere between the alternator out and the regulator input there is alot of resistance.
For the moment, the fact your battery doesn't see system voltage (16 V) is a good thing.
Since the battery is at 12.5 its probably not taking any charge so I've shown the ammeter in the middle.
If it is showing charge - then there's a short or somehting on that line that shouldn't be.
upload_2019-6-13_18-35-39.png


The next step is to find the resistance. Check each of these points for voltage drop.
upload_2019-6-13_18-42-13.png

Not checking the ammeter posts because it should be the same as J inside as there's no flow that line.
You can check for voltage drops in the battery feed line with engine off and something on. But do it later. One problem at a time.
 
with bypass wire in place the alt BAT stud is showing 13.8, the blue wire on VR is about 5V at idle and decreases with higher RPMs. I get headlights/dashlights flickering at idle which disappears with increased RPMs. (I have crackedback's headlight relays in place BTW). Anyway I can live with this but think I will need to watch overcharging battery..art least want to run it until it reaches full battery charge and see if charging current gets knocked by VR buty 13.8 is probably good if I remember correctly.. comments appreciated. thnx
don't know what you did but its not good.
Whatever route you created seems to have more resistance.
shake_head-gif.gif

Get a charger if you don't have one.
Charging Battery with Alternator - Warning
 
I have EI conversion btw. Yes, I charged battery with a charger up to at least 12.5 before starting up. Was only talking about running for a while to see if alternator charging rate would eventually drop from 13.8 to something lower. Not sure what you mean "don't know what you did..". As I said, I just added bypass wire (from alt BAT stud to the starter relay) - nothing else. What makes you say resistance has increased? Change in VR blue wire read? Do you happen to know what voltage regulator blue wire should read at idle and with increased rpm? When you mention test probing you are not saying if car is running or not or what the read-outs should be. Sorry, my typos do not help. Appreciate your time and insight on this. I think there is a bulkhead connector diagram that shows which terminals are which - will have to find it again.
 
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Alright. Let's go over how electric circuits work. Then you can tell us.
We'll start with a basic open circuit.
If there is a battery at 12.8 Volts and three open switches, what is the voltage on the battery side of each switch?
upload_2019-6-13_21-34-28.png

And for extra points, how much current is flowing?
 
What happens to the voltage at those same points with the switch to the closed small lamp closed?
upload_2019-6-13_21-46-18.png

And through which wires and switches does the current flow?

The answers should be:
a) Nothing, it stays 12.8 volts at all three switches.
And with the switch closed, it should 12.8 volts right up to the lamp filament.

b) Current flows through the red wire from the battery through the switch to the small lamp, through the small lamp to ground.
and to be complete then through ground back to the battery negative wire.

If you didn't get these answers, then we need to back up and figure out why.
 
hey ( r u sitting down?) I think was looking at green vs. blue wire on VR! pretty sure the IGN is the one we wanted to check-yes, it's blue. Anyway will have to look at that voltage again tomorrow. Will likely be closer to range we are looking for when charging system is working.
 
Two more here.
If you follow this then I think you know the answer to your questions about what the voltage should be at the regulator.
And also whether the voltage drop test should be done with with the engine running or not.

Taking the same scenarios with one switch closed, but three poor connections.
What happens now?
upload_2019-6-13_22-19-34.png

What's the Voltage at the switches?
And is there any current flowing?

I'm sure you got that. See if this next one makes sense to you.
Same three poor connections in the wiring.
Each poor connection has resistance to flow.
When the switch to the small lamp is closed, voltage drops across each resistance current is flowing through.
upload_2019-6-13_22-14-1.png
 
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To return to the voltage regulator. If the voltage regulator is seeing anything less than the set point, say 14 Volts, its going to try to increase the alternator's output voltage. If the regulator is seeing voltage above set point, its going to decrease the alternator's output voltage. Resistance to flow between the alternator output and the regulator's measurement point causes the regulator to do the wrong thing.

The more current, the more resistance and the more the voltage drops.
So if the electromagnet is a big current user, there's a going to be a big voltage drop across the first poor connection.
There will be less drop across the second poor connection because there's only a small current going through the lamp.
upload_2019-6-13_23-3-0.png


Batteries have a lot of stored power, but under big loads voltage does drop.
So in reality we see something like this when a heavy load is placed on the battery.

A battery's stored energy can only be guestimated from its voltage. An ammeter on a charger will show when its full but not condition. To test the condition either a hydrometer or a load test is needed.
 
thanks - I got most of that. we'll check reading at correct terminal on VR with it running later today. Another question came up your expertise can address: If I do ammeter bypass wire (alt to starter relay) and just leave the rest of wiring in place that routes through the ammeter, will this reduce load that goes through the ammeter and help reduce chances of frying? I know others doing this disconnect the ammeter and join it's wires together and some don't.
 
You need to find the problems and fix them.
That's what will fry! Resistance causes heat. The more current, the more heat!
Simple as that.
Go down the line from the power source and find voltage drops and you'll know where to look for wires or terminals that need fixing.
A voltage drop can be in the ground side as well.
When you know there is a problem(s), you can measure drops directly instead of to ground. Place the positive probe on the power source and use the other to measure the drop at each junction or terminal down the line.

Pay attention to what the ammeter is showing.
Its scale is approximately 40 amps to 40 amps.
Nothing you've done so far indicates one way or another to the ammeter as a problem.
Unless its been damaged it show you how much current is going through it. If it shows over 20 or 30 amps for more than a minute or two then you need to find the problem. If it pegs there is a BIG problem - and its not with the meter. Something will melt because these circuits are not made to handle that much current for any length of time. The weakest wiring will fail first but it could be several places. If you let a battery charge at 30 amps for a long time it will cook, and the alternator may be damaged as well.

Engine off, do the same type of check for voltage drop in the battery line as discussed above for the alternator (and shown in post #5).
Parking lights will draw enough to show some voltage drop. The ammeter will show you approximately how much current is flowing out of the battery.

If you don't find the resistance then its just all guessing.
If well made your jumper from the alternator out to the starter realy will provide a more direct path for charging the battery. It does nothing to help the power get to the main splice and beyond to everything else.
PS. your headlight relay (the wires with the fuses) ought to be attached to the alternator output stud. hopefully you now can figure out what happens if its attached elsewhere.
 
Seems you have t.m.i. already but I'll add what I know. 12 volts goes into ignition switch. At switch on 12 volts goes out on a couple of wires. One goes to fuse box. Can we assume you are getting 12 volts to radio, wipers, signals, etc..? Another of the terminals on your ign' switch has 2 blue wires going out of it. One of those wires goes to inst' panel to feed inst' voltage limiter. Other goes through bulkhead to engine bay. It feeds 12 volts to system voltage regulator, etc...
So there are very few places where there would be a weak connection/voltage drop, the ign' switch, the wire itself, the bulkhead terminals.
Bypassing the amp gauge in the engine bay renders the gauge wrong, pretty much useless. May as well take it out of the circuit/current path but... both wires onto one amp gauge stud is not the best method in the case of rally inst' panel. I won't go into the "why not?" here except to say that entire gauge is still hot if the wires are on it.
Optimal solution is replace amp gauge with a volts gauge. Put red and black amp gauge wires together with crimp connector, solder, heat shrink. Volt gauge would connect to switched 12 volts, the blue wire that feeds inst' voltage limiter, or the wire that feeds park brake lamp ( I forget what color it is ).
 
all good ideas thnx - yes am getting power to all in car -all works fine. I already have a volt gauge installed so am not concerned with accuracy of ammeter - it has always just barely moved from from dead center - which maybe says it was doing pretty well - examples: 1) with key just switched to 'on', turning on the headlights would move it slightly over to the discharge side. 2) with car running, turning on headlights and wipers would move it a little over toward the charge side. But overall it's function is not a concern to me - just do not want it to be a source of future problems. SO...will check to find poor connections/voltage drops. Part of my issue is not being able to access ammeter - dash removal is not something I want to tackle. Everything electrical on car is working fine BTW. I had the bulkhead connectors apart last year and cleaned up where needed - none looked really bad. Will have another look. Am I not taking the charging load off the ammeter by installing the bypass? (I understand it is still in line and getting power).
 
with car running, turning on headlights and wipers would move it a little over toward the charge side.
Something is wired wrong!
You have to ask yourself why is current flowing to the battery when you turn on either the wipers or the lights?

If Redfish says not to hook the ammeter wires together on the ralley dash, then that's good advice. It's an example of why I hate to make generalizations on modifications.
 
no. Had these cars in the 60's and that is pretty much how the crappy ammeter worked. And current should be flowing to the battery when it has a load on it - ..think about it- that is exactly why you have a charging system. appreciate the tips. fwiw, I never said I wanted to hook the ammeter wires together under the dash for same reasons he is thinking I am sure. I'd like to maybe join them inside the engine bay where accessible.. Anyway you guys gave a lot of good info and will keep me busy for a while - if I have a eureka moment I will share - thanks again.
 
No. The only difference is you've thought this longer than I have, or should say I did.

Current flows to the battery when the battery wants to be charged.
Current flowing to the wipers never goes through the ammeter unless the alternator can't provide it.
Current flowing to the lights never goes through the ammeter unless the alternator can't provide it.
The fluctuation or discharge we see at idle with lights, wipers, and brakes on is when the alternator can't provide all the power at 14 Volts.
Alternator's potential to make power is very rpm dependent.
When an alternator is maxed out, voltage drops. When it drops to battery voltage, the battery becomes the highest voltage power source. Current flows out from the battery to the devices.

A characteristic of the battery is that it can carry a surface charge. When a fully charged battery is connected to power source at 13.4 to 15.0 Volts it develops a charge above 12.8 Volts. With a voltmeter on the battery it may show 13.0 Volts or higher when the power source is removed. The surface charge has little energy in it. It disapates slowly over time or quickly when subject to a load (flip on the lights for 20 seconds or so.)

If current flows in the charge direction through the ammeter goes to anything but the battery something is wrong.
The only thing that should be on the battery side of the ammeter is the battery.
With a jumper wire between the alternator and the battery positive, charging power should go right to the battery. There should no longer be flow to the battery in the original feed/charge line. Only flow in that line should be discharge (when starting) or when the alternator can't supply the power.
 
"With a jumper wire between the alternator and the battery positive, charging power should go right to the battery." That sounds good to me. OK so I get 12.5 or so on blue IGN wire of voltage regulator with car running. With engine running, I tested some of the fuse block hots and found the one for instrument lights had a voltage drop to 11V when I turned the lights on with headlight switch. This fuse has 2 wires tapped into it that supply power to 1) the LED lamps in the after market small gauge cluster..and 2) something else I still need to find...we'll see . Because power source for instr. lights circuit comes form headlight switch, I am thinking corrosion/weak connections/other issues in that switch could be reason for drop - does that sound like a possibility?
 
yes it does. but 11V not too bad for a 50 yr old switch with a lot of wires and use on it. OK, so we check out the headlight switch - at least shoot it with some contact cleaner. All else working well - BTW the new electronic but original look VR is doing OK. The old original really showed it's age inside - likely was questionalble at best.
 
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