question on bulkhead connector bypass

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When I troubleshoot charging problems (for example) I tend to group the system into "sections" more or less

1...You have the main charging circuit This is what the MAD bypass does.......improves that high amperage circuit. This is the black charging wire through the bulkhead, through the ammeter, out the red wire and back out the bulkhead to the battery. Not only is the wiring too small for modern higher amp alternators, the connections at the bulkhead connector are not adequate, the ammeter itself can have problems, and in rare cases, the welded splice can fail

2...The field/ VR circuit. This circuit, too has problems. Voltage drop in the ignition switch and connector, the bulkhead terminals, the VR connector on newer cars, and problems with the alternator brushes

3....The ground circuit. Interconnections between the battery, body, engine (alternator) and VR

4....The main components, the battery, VR and alternator

The entire system is/ can become a "loop." The VR senses battery voltage through the ignition circuit, AND THIS MUST be "close to same as" battery voltage to work properly. The VR adjusts field current to cause the alternator voltage to rise or fall until "the loop" is satisfied that the voltagel is at the VR set point.

THE ONLY TIME this situation is not "true" is something like an aftermarket "one wire" setup which senses voltage right at the alternator output. post
 
TBeast I need like a mini-diagram of how a relay would be installed between ignition side of VR to the positive battery post. just not seeing it yet.
 
OK - I removed the blue ignition wire from bottom of VR ans connected anothe wire and ran it tothe positive battery post. Running the engine, the flickering headlights are gone and the volt gauge is showing the charging current to the battery at about 13.4 when the headlights are on. maybe slightly less when they are off. What this may be telling me now I am not sure.
 
It is telling you exactly what I told you earlier. There is VOLTAGE DROP in the path from the battery, through all the harness and connections that is dropping the sense voltage to the VR IGN terminal. The drop is likely not "stable" that is, it "arcs across" and changes resistance.

Just what is it that you are using to read this board?

..........and this is the reason some guys install a relay to allow the relay to supply a more direct and more stable, less drop path from the battery to the VR.
 
OK - so sounds like all I have left to do is add a relay to this last mod -any tips on what that will look like? thanks very much
 
I'm on a mission to learn more about this overall system and any mods that can improve it short of replacing the harnesses. Looking at all the diagrams is one thing but understanding how factory intended it to work is something else. Right now I'm thinking why did one side of VR go to ignition circuit? could it have gone elsewhere for the purpose that terminal served. IS going direct to the positive battery post essentially the same thing. I appreciate the knowledgeable people here who sorta stick their necks out a little answering questions, as there are often some differing opinions ,or at least more than one way to skin a cat..
 
I ain't much help Dave, its voodoo to me. Do a search on my threads, I've had electrical problems, something might "click"?
 
understood. Hey, like my mechanic says, (who reminds me more and more of Jerry Seinfeld's), don't mess with that! If it ain't broke, leave it like the factory intended, those people actually were automotive engineers. lol. Lot of variables with this stuff - think you have a plan and then one of the components can start going bad and throw a wrench into the works.. I feel like I cleaned up that bulkhead connector mess enough to feel pretty good going forward - maybe it lasts another 50 years - I know I won't!
 
Dave NEO said:
I'm on a mission to learn more about this overall system and any mods that can improve it short of replacing the harnesses. Looking at all the diagrams is one thing but understanding how factory intended it to work is something else. Right now I'm thinking why did one side of VR go to ignition circuit? could it have gone elsewhere for the purpose that terminal served. IS going direct to the positive battery post essentially the same thing. I appreciate the knowledgeable people here who sorta stick their necks out a little answering questions, as there are often some differing opinions ,or at least more than one way to skin a cat..
Click to expand...

Anything wired directly to the battery is on/hot at all times. You don't want create battery drains. There is only 1 switched hot source in the engine bay. That's the blue wire from ignition switch. At switch on it energizes the voltage regulator/alternator field and spark/ignition at minimum. It might also supply IVR and some warning lamps inside in many models.
In later models it also supplied everything they added in the engine bay requiring switched 12 volts. Electric choke assist, idle stop solenoid, etc...
If you can't get sufficient current though the ignition switch and out to the engine bay, the blue wire could energize a relay out there ( The same remedy applied to the headlight circuit ).
 
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I agree - wiring up anything constant hot, fused or not, is asking for some possible drains/shorts/etc.
 
so here's something I'm mulling over - you got an alternator that can put out 60 amps or so (when it's is demanded). So you have a system in your old car that has few accessories, you never run the blower motor or radio, basically you are just running the car with running lights. So your electrical system is never really calling for a lot of amps to run through it. When Mr. battery eventually needs a boost, VR says send me 13.8 volts or so to get battery up to where it should be. VR then says OK, ease up on the voltage, alternator complies. My point is there is not a high amp current running through the electrical system and the bulkhead connector ever in this scenario - right? I'm thinking of why the factory changed charging system wiring for police cars and other high amp usage vehicles and other changes later on for all cars vs. the way we tend to use these cars in fair weather today with just the basics. (OK, some of you have to have A/C and big sound system!) any comments?
 
Leave the lights on or any weak battery scenario is a call for high amperage. Modern alternators can produce 100+ amps. That's not a problem when the system is adequate and initially designed to handle unexpected scenarios
For us, It's the resistance in undersized wiring, degraded connections, etc.., that lets the smoke out.
 
yes no doubt. I think what I'm asking is: assuming you are not running more than the engine and some brake and turn signals, how many amps are being drawn when battery needs a charging current? Is it a number related exactly to what is being run (i.e. specific lights, etc) or is it a maybe a more fixed amperage ? Seems like it would not be the max amp output of the alt .but maybe it is.?
 
The voltage regulator controls the alternators output at varying demand and rpm. I don't think there is a constant.
 
yes but I that's controlling volts - amps has to be another thing.
 
Maybe you should Google the relationship of volts, amps, watts. All different but relative. So the "voltage" regulator is controlling both.
Examples... A bad 12 volt battery that stores very little amps can show 12 volts at no load. Put a load on it consuming the amps and volts will drop like a hammer.
Bypass the voltage regulator full fielding the alternator, rev it up, get all the amps it can produce, system voltage could hit 16 or more, pop light bulbs, etc...
 
Not sure of that. Revving can max the volts it puts out but not the amps. It would still be a 12 volt alternator putting out 13.8 to 14.8 volts which most 12V bulbs can handle - but again that's not exactly what I'm getting at anyway- so no worries, appreciate your input. Yes I get the volt/amps/watts thing - been working radio tech many years but never messed w/auto electronics. One thing I do know though is any voltage regulator regulates volts.. and when working properly prevents overcharging of battery that would result form excessive voltage charging rate. I agree you I'm probably missing something key here and need to study it so I will try. thanks .
 
this is getting closer to my question /point:
"Alternator Output Supply and Demand
With all of that in mind, it’s also important to understand that the output of an alternator is tied to the demands of the electrical system in addition to its inherent capabilities and the speed that its input shaft is rotating at any given moment.
In essence, while maximum alternator output is dependent on the rotational speed of the input shaft, the actual output is load-dependent. That basically means that an alternator will never generate more current than is called for by the momentary demands of the electrical system.
What that means, in the real world, is that while an underpowered alternator can cause problems by not meeting the needs of your electrical system, a substantially overpowered alternator represents a lot of wasted potential. For instance, a high output alternator might be capable of putting out upwards of 300A, but it won’t actually provide more amperage than a stock 80A unit if that’s all the electrical system ever tries to draw."
 
found excerpt below helpful overview of auto charging system basics if anyone else is interested. Article had some other interesting auto electrical info. fwiw
Explained what I wanted to understand: my old wiring and bulkhead connector are not constantly dealing with 60A max of my alternator or anything close, but most likely (on my car anyway) quite a bit less.

Charging System Basics

Current Demand and Flow:
If you have an alternator that can produce 120 amps of current (max) and the the total current demand from the electrical accessories (including the battery) is only 20 amps, the alternator will only produce the necessary current (20 amps) to maintain the target voltage (which is determined by the alternator's internal voltage regulator). Remember that the alternator monitors the electrical system's voltage. If the voltage starts to fall below the target voltage (approximately 13.8 volts depending on the alternator's design), the alternator produces more current to keep the voltage up. When the demand for current is low, the full current capacity of the alternator is not used/produced (a 120 amp alternator does not continuously produce 120 amps unless there is a sufficient current draw).
 
The old Mopars did not have an internal voltage regulator. They had a diode Bridge inside that changed the alternating current into DC current . The voltage Regulators mounted on the firewall. You can have 120 volts coming out of that Altenator going to that voltage regulator.
 
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