Underhood Ammeter Bypass

[cbarge]

As requested,A couple members,some experienced,some newbies,asked for me to do a detailed pictoral of adding the extra wire under the hood that will keep your car alive and save your sneakers for walking the dog.
I done this soo many times I never really did any pics of it.
Using Maggie's 69 Fury III "Frankie" as the demonstrator.
Besides, I wanted to do this anyways since it was never done on this car.

 

[cbarge]

Step 1. Disconnect battery.
Step 2. At the back of the alternator,run a 12 gauge or heavier wire starting at this 7/16" nut.

 

[cbarge]

Run the wire the same way as the original harness.
You can hide the wire or use wire looming but for this thread I left the wire exposed for clarity..

 

[cbarge]

The other end stops at starter relay.
Depending on what year most are either on the firewall or left inner fender..

 

[69psf]

Great info - thanks for that!

 

[cbarge]

At the relay use a fusible link. I used an 18 gauge with my 12 gauge wire.
Fury only has a 38 amp alternator.
On my other car,I am running a 78 amp alternator and used 10 gauge wire with a 14 gauge fusible link.

 

[cbarge]

I used male and female insulated spades for future repairs.
Thus wat I can replace the fusible link and not cut into the wire.

 

[cbarge]

Hook up the fusible link to the battery stud at starter relay. Some cars have 1/2 wrench or others need 9/16' for the nut..

View attachment 378441

 

[cbarge]

Button up the relay tidy up the wires reconnect the battery and enjoy!
Our guinea pig shown here from today..under construction,LOL

 

[cbarge]

It took longer to do the thread compared to the wiring,LOL!!
But I cannot stress enough how important this 15 minute job is .
What it does is piggy back on the ammeter circuit. This wire takes 50% of the load away from the ammeter itself.
We all know the ammeter gauge is the achilles heel in our beloved old Mopars.
The fusible link is a safeguard should the alternator short out and not burn the dash or car to the ground.

You wil notice that the ammeter gauge will not swing as crazy as before and will not read 100% accurately.
But still works--until is does short out but the car will still function normally on a day to day basis.
An option is install an afermarket volt gauge.
Simpy hook it to a switched 12 volt source and ground it to body. done.

In laymans terms the Red wire at starter relay goes through the bulkhead and eventually to the ammeter gauge--which is hot all the time.
Hot I mean live as in anything that is run by battery no ignition key needed (headlights,hazards,dome light lighter,etc)
The black wire on the ammeter goes to the ignition switch which as you know powers anything that needs the key on.
So when the ammeter shorts out you have NOTHING!
This simple little addition is worth its time,trust me.

I cannot take credit for this mod.I first read about it in MOPAR ACTION
20 years ago writen by Richard Ehrenberg.
Hope this helps.

 

[C Sickness]

The ammeter is a gauge that measures current flow. The Needle responds because it's connected to a small auxiliary winding that senses current flow through the main conductor in the meter. The meter is manufactured as what one could describe as "shorted". the "in" and "out" terminals are connected together. As long as this continues, all is well.

What would make you walk home is a failure. The main conductor in the ammeter burns "open", resulting in a circuit disconnect. Battery charging ceases, and power is lost to the ignition switch.

People like to say a failed electrical item is "shorted", when, actually, it has "failed open".

This mod provides a secondary, "back up" circuit. Should the ammeter fail open, power is still provided to the key switch through the additional circuit.

Probably the most important function of my Fluke meter is to analyze suspect components.
Who still has their designed resistance?
Who is shorted?
Who is open?

 

[cbarge]

The ammeter is a gauge that measures current flow. The Needle responds because it's connected to a small auxiliary winding that senses current flow through the main conductor in the meter. The meter is manufactured as what one could describe as "shorted". the "in" and "out" terminals are connected together. As long as this continues, all is well.

What would make you walk home is a failure. The main conductor in the ammeter burns "open", resulting in a circuit disconnect. Battery charging ceases, and power is lost to the ignition switch.

People like to say a failed electrical item is "shorted", when, actually, it has "failed open".

Thanks.
For the Newer members or the less electrically versed I did not get too technical.
I kept it simple.

 

[furious70]

It is important to emphasize that when you do this the ammeter no longer indicates correct charging since the new circuit is on the 'back side'. The ammeter just measures the direction of flow, which can be either way now and still have a fully functional system.

 

[Turboomni]

May I ask why a fusible link and could you just use a fuse? Thanks for this as I think even I could do this!

 

[The Captain]

I have done this numerous times and the ammeter works but reads backwards.

 

[furious70]

I have done this numerous times and the ammeter works but reads backwards.

On a car with no other electrical mods, most likely because the new charge circuit is path of least resistance. But if you start adding a big stereo, a fuel pump, etc - where you source power for those will influence which direction current flows.

 

[Ross Wooldridge]

@cbarge Nice write up! Thanks for that.

For clarification - is the alternator connection for the new bypass wire the same for older round back style alternators? Is it obvious?

Also, again, for clarification for those of us clueless about electrical - does one leave the original wire to that stud on the alternator (the black one with the red insulator in your first picture), or disconnect it and leave it dangling? When the nut goes back on the alternator with the new wire, will there be two wires (the new and the original), or JUST the new wire there?

As well - how about detailing the "ammeter feed bulkhead bypass" procedure - like my Monaco had done at the factory as per the police wiring. We gotta get that big power OUT of the bulkhead spade connectors. That's the biggest fire starter there is.

 

[cbarge]

May I ask why a fusible link and could you just use a fuse? Thanks for this as I think even I could do this!

You can use an inline fuse for sure! No problem both work the same way in principle.
I am used to using the fusible links that's all.

 

[cbarge]

clarification - is the alternator connection for the new bypass wire the same for older round back style alternators

Yes it is. You will have two wires at the stud of alternator '--original and new addition

 

[cbarge]

It is important to emphasize that when you do this the ammeter no longer indicates correct charging since the new circuit is on the 'back side'. The ammeter just measures the direction of flow, which can be either way now and still have a fully functional system.

Which why I recommended an aftermarket volt gauge for those who really like to keep tabs.