Bypass ampmeter through bulkhead

-
B

bills73duster

Member
Joined
Apr 3, 2023
Messages
24
Reaction score
27
Location
Jefferson City Mo.
I've decided to bypass the ampmeter in my 1973 plymouth duster. Using the Mad Electrical option.

Has there been any though about instead of splicing the black wire under the dash that goes to the welded slice
 
bills73duster said:
I've decided to bypass the ampmeter in my 1973 plymouth duster. Using the Mad Electrical option.

Has there been any though about instead of splicing the black wire under the dash that goes to the welded slice
Click to expand...
Not sure your question comes through? Not sure what you are asking?
 
Just a note...

Not sure of the year but as I recall at some point the Ammeter became a remote meter meaning that all the current of the car did not go thru it but stayed in the engine compartment and a remote pickup ran the gauge inside the car.


As for your question as I understand it.

If you are asking about splicing the red into the black at the main splice on the black that could be done but seems like a lot of extra work.
 
bills73duster said:
I've decided to bypass the ampmeter in my 1973 plymouth duster. Using the Mad Electrical option.

Has there been any though about instead of splicing the black wire under the dash that goes to the welded slice
Click to expand...
I typically just bolt both sides of the amp gaug connection to a single lug on the gauge. In many cases, I add a volt gauge or have the gauge converted to a volt meter.
 
I apologize for not being clear enough. Please review the pdf file.
Instead of splicing the lead from the alternator under the dash and on to to starter cylinoid.
I'm proposing splicing the lead from the alternator in the engine bay and continuing on to the starter cylinoid and in turn feeding the fuse box, light switch and ignition switch.
 
Personally I feel your option gives the best of both worlds

(I would leave the Ammeter connected)

You are bypassing the largest current load in the system (charging the battery) with the wire direct from alt to starter relay battery post. And leaving all of your cars original wiring alone (except for cleaning and replacing wornout bulkhead connectors etc.)

The up side is the load for running the car is shared on 2 bulkhead connectors rather than 1.

I see no down side to this.



This is my version. It leaves all oem wiring intact.

Screenshot_20240306-130341.png
 
Last edited:
I have spent all winter repairing and upgrading the wiring harness .
And I didn't want to make any mistakes.
Last spring the duster failed to start. After I started digging into it. I was amazed that it hadn't caught fire.
The bulkhead connector was burned almost melting. So i.knew I had to do something. I'm the original owner.

If it weren't for "A Bodies only" and the forum. I don't think it would have gotten done
 
I did essentially the same thing @Dana67Dart did. I left all OEM wiring intact and ran a battery charging wire from the alternator to the starter relay batt terminal as he noted. The only diff is I put the fusible link over at the alternator end.

Been that way for 2 years now and seems to work just fine. As he says, it gets rid of trying to run all that current through a bulkhead terminal...twice! (One on the way in and another on the way to the batt.) Plus you have to look really close to see that the wire was added. :thumbsup:
 
My wife and I were married in 1972.
Bought the car new I the spring of 1973.
Just preventive maintenance and tires kept it going.
Did a ground up restoration 8 years ago.
It will be something to leave our children and for them to have fun with.

FB_IMG_1680747710908 (2).jpg


FB_IMG_1680747710908 (2).jpg


FB_IMG_1680747710908 (2).jpg
 
nah, what I did is the best. ;)
Follow what the factory did when faced with situaiton where the 1/4" push connections were likely to be stressed.
It is more work.
Plus side is the gage is useful and the fusible links are in series, not in parallel.
 
That is a good point. But sence the l largest current load has been moved and being diverted directly from the alternator to the battery. Wouldn’t the current going through the bulkhead at location "P" and 1/4 in. connectors drop to come close to the other connections through the bulkhead and greatly reduce the chance of heating problems?
 
Ok. It depends on what you beleive.
How much current does the battery draw? and for how long?
How much current do the other items draw? and for how long?

So it comes down to the condition of terminal P, how many accessories are going at once, and how long they are on.
A headlight relay system diverts a 9 to 12 amp draw so it never goes through P.

The direct wire from alternator to battery is easy. But.
What happens or has happened when the battery is drawing 10, 15 or more amps for long periods of time? Do you want to know that? A voltmeter will never show that unless its due to a regulation failure. Even then it may not show high voltage if the failure is a poor connection in the ignition-field wiring. Both voltmeters and ammeters are useful, but they show different things. That's not bad or good, just tradeoffs.

Yes. Using the alternator while driving to recharge a battery that has been run down can cause the connections on that circuit to see higher currents than normal. That certainly can cause heat damage to all connections on the circuit. The direct connection from alt to battery protects the connections against that situation. However that may not be the only damage done.

Why has MAD made the ammeter the bogeyman? What is the example they use? Was that the battery or the accessory that caused that much current? I think the answer is in their own text. They wrote, wrongly, that all power for running the vehicle comes from the battery through the ammeter.
 
Looking at your PDF.
That arrangement does work better in terms of fusible links each protecting just one path.
However it makes the power from the alternator go through two fusible links, then back through terminal P. Yes if P has enough resistance current will flow through the parallel wiring even though its longer. So the load will split when the resistance in both paths is close to equal.
It's all tradeoffs.

Here's what the factory did for A-bodies in '73
1709820693890.png


You could leave the standard alternator output wire to P, and then instead of an 8 gage wire use a 10 or 12 through the grommet.
The factory probably used 8 ga because of the heated back glass option. And I *think* '73 has the molded insulation on the R6 wire connection at the alternator ring terminal. If so, then it was easier to cut it out than leave it in when installing the option wiring on the prodution line.

Here's pictures of a '73
www.forabodiesonly.com

How rare is electric rear defrost?

Not an accurate one. I've had acouple good offers for the switch. But wanna give someone a chance to buy it all complete first before I separate it all out. Depending what shipping ends up being, I’d be interested in the whole setup.
www.forabodiesonly.com www.forabodiesonly.com

and a '74. Grommet in same location.
www.forabodiesonly.com

Dash Power Feed Confusion

Hello members, I am having some trouble getting some wiring sorted out on the car, mainly where the gauge cluster gets power from and where my alternator lead plugs in. There is a harness connection at the firewall with a red wire and 2 black wires, heavier gauge, shown below. The red wire...
www.forabodiesonly.com www.forabodiesonly.com

One thing Redfish has said to watch for in early '70s cars is water leaks. He's observed that was somewhat common on those cars and caused electrical problems in the instrument area including the ammeter connections.
 
Last edited:
I just connected the wires together under the hood, taped it up, and called it a day. It bugged me that the gauge didn't work, until I realized that the only reason I was looking at it at all was because it didn't work. I have AAA if something goes down, and 99% of the time, I get a warning via some other method that there's a charging problem.

I ran the alternator wire straight to the stud on the starter relay, and if I want my ammeter, I'll punch a hole in the firewall and wire it direct. I don't miss it.
 
I think one of reasons for the fusible links is that the battery can produce hundreds of amps for minutes regardless of whether the engine is running or not.

A direct short on the car side if the fusible link, in theory, will melt before too much damage is done to the car wiring.


The alternator can only produce it's max amps (50 60 100) WHILE the engine is running. So there is no overwhelming need to protect the car from the alternator, in theory!

I agree the ammeter AND a volt meter are very useful.
 
As for as the condition of terminal “P”.

Terminal “P” is new with make and female bulkhead plugs, new packark 56 terminals and new 12 gage wire (R-6 12 BK) witch matches the original specifications.

As for as the accessories. During shows and contest. The only accessory used is the original AM radio. No heater being used. As I only drive it during the day and with good weather. And during spring and summer.

I personally can do with or do without the ampmeter. It has given me no issues for over 50 years. Upon inspection. It showed no corrosion and both terminals were still shiny and clean.

The bogeyman only appears in your imagination. And comes to cause doubt.

With the charging current bypassing the

“ampmeter “. The chances of any issues are slim to none.
 
Mattax said:
How much current does the battery draw? and for how long?
How much current do the other items draw? and for how long?
Click to expand...
bills73duster said:
As for as the accessories. During shows and contest. The only accessory used is the original AM radio. No heater being used. As I only drive it during the day and with good weather. And during spring and summer.
Click to expand...
OK. If the lights, wipers, heater fan are never used then the current loads are as follows:
Ignition and field current - approx 5 amps
Brake lights - about 4.5 amps
Turn signal - which turns off one brake light and is also briefly used we'll ignore it.
So that's about it for your projected uses.
For someone running the heater fan, lights, etc, the alternator will need to provide 25 to 30 amps to run them all at the same time.

The battery after starting typically draws 15 amps to 20 amps for less than a minute. After 5 minutes of driving it draws basically zero. Depending how long it had to crank it could be a little more or a little less.

bills73duster said:
The bogeyman only appears in your imagination. And comes to cause doubt.
Click to expand...
Not mine. :)
I'm not the one saying the ammeter is going to blow up people's cars or set them ablaze. LOL
I am saying a working ammeter provides useful information. In fact if one pays attention, an operator can spot problems early and can even avoid a meltdown due to overcharging or a short.
bills73duster said:
With the charging current bypassing the

“ampmeter “. The chances of any issues are slim to none.
Click to expand...
 
Dana67dart,
I've decided to go with your example, as I've said earlier. The ammeter hasn't caused any issues for over 50 years. Just last year when I noticed the melted bulkhead connectors. Witch it could may not have been caused by the ammeter.
Demonx2. HiI am confused about what you referred to as a "fusible link on the alternator end". Are you placing the fusible link attached to the alternator? Or in line?
 
bills73duster said:
Witch it could may not have been caused by the ammeter.
Click to expand...
You're not sure?
Take some time and think about how the ammeter could have caused the bulkhead terminals to melt.
Melting is caused by heat, and heat is a reuslt of electricity passing through resistance. So either there was too much current, or the connection was loose, oxidized or similarly failing. This can be cumulative over time because excessive heat will further deteriorate a failing connection.

Now lets look at an automotive ammeter.
Does it create power?
Does it use power?

So what can go wrong?
Well it has two external connections and two internal connections. So like any connection, they can deteriate, become loose, get wet, and create resistance. They also can get hot when too much electricity flows through them. The difference is we can see directly how much electricity is flowing through the ammeter (and the wires connected to it). That's what the meter does.

Here's the back of some ammeters.
There are two studs attached to a metal plate. Usually pressed in. The studs and plate are insulated from the chassis because they are hot.
1710511387336.png



1710511298339.png



The plate goes around the needle. When current is flowing past the needle the electromagnetic field causes it to deflect.

1710511945131.png


So now, after seeing how it works, hopefully you can answer the question if the ammeter could have caused a bulkhead terminal to melt.
 
You must log in or register to reply here.
-

Back
Top