Ammeter bypass turning over alternator

[kewen300]

Good evening everyone.

So, 66 Barracuda is not charging. I went to do the ammeter bypass. Hooked a line to the alternator(back wire /green wire). Black wire and the other side i hooked to the starter relay lug on the firewall. Immediately the motor started to take off on me when I put the battery back on. What did I do wrong?

 

[Professor Fate]

I don't know why you did what you did, but that isn't an "ammeter bypass".
All you did was hook a hot wire to your starter relay.
An ammeter bypass is done behind the dash- basically unhooking both connections to the ammeter and connecting the wires together.
BTW, a bypass isn't necessarily going to fix a "no charge" issue- you need to start diagnosing what the problem actually is.

 

[1WildRT]

Look at the starter relay, chances are something attached to the battery lug is contacting the starter lug...

 

[kewen300]

I don't know why you did what you did, but that isn't an "ammeter bypass".
All you did was hook a hot wire to your starter relay.
An ammeter bypass is done behind the dash- basically unhooking both connections to the ammeter and connecting the wires together.
BTW, a bypass isn't necessarily going to fix a "no charge" issue- you need to start diagnosing what the problem actually is.

Many posts suggest this is the easiest way to go instead of getting to dash and cutting wires. Im deep in the diag. The ammeter is the last hold out.

 

[kewen300]

Look at the starter relay, chances are something attached to the battery lug is contacting the starter lug...

Thank you. I'll take a look tomorrow after work and post back with updates.

 

[Dana67Dart]

Post a photo of what you have

 

[RustyRatRod]

Post a photo of what you have

I'm skeered.

 

[junkyardhero]

I'm skeered.

imma skeered too! hold me! tell me it's gonna be alright

 

[junkyardhero]

Many posts suggest this is the easiest way to go instead of getting to dash and cutting wires.

source needed please

 

[RustyRatRod]

Many posts suggest this is the easiest way to go instead of getting to dash and cutting wires. Im deep in the diag. The ammeter is the last hold out.

Trust me. You're misreading something.

EDIT. Either you're misreading something, or reading incorrect info.

 

[Deltatech]

Well at least you know you have good solid battery voltage to the blue wire from the field terminal.(this is what you probably connected to your starter relay lug that turned it over)
Good VR ground?
Have you done a full field test?
It only takes 5-10 minutes to bypass the ammeter behind the gauge panel.
You dont have to pull it all the way out or cut any wires,
take the gauge panel out just far enough to get a socket on the nuts off the posts on the back of the ammeter and put a small bolt through the O terminals connecting both wires , tape it, and done.....

 

[Professor Fate]

Many posts suggest this is the easiest way to go instead of getting to dash and cutting wires. Im deep in the diag. The ammeter is the last hold out.

Keep a fire extinguisher handy.
And I am NOT joking.

 

[67Dart273]

Good evening everyone.

So, 66 Barracuda is not charging. I went to do the ammeter bypass. Hooked a line to the alternator(back wire /green wire). Black wire and the other side i hooked to the starter relay lug on the firewall. Immediately the motor started to take off on me when I put the battery back on. What did I do wrong?

First YOU DO NOT change anything about the green wire on the alternator

SECOND what you probably did, was to hook the alternator output stud (correct) to the 'square' looking terminal, WRONG on the start relay. What you want to hook to iis the great big stud with the nut on the start relay.

BUT IT AINT THAT SIMPLE

you need big wire, like maybe 3X no. 10s if you don't have big, 3x no 10's in parallel. Or a piece of no.8 depending on how large the alternator is. AND A FUSE or BREAKER, depending on the wire size (protect the wire) and depending on the size of the alternator.

You need large enough wire ampacity to carry the alternator, and you need a small enough fuse / breaker to protect the wire.

ALSO you need to CHECK the two ammeter wires WITH THE BATTERY ground disconnected, and be CERTAIN that they are not damaged, AKA the wire ends, then bolt them together and tape them off "safe."

AND ALSO you need to examine the connector terminals through the different sections of the BULKHEAD CONNECTOR and replace damaged ones.

 

[65Vart]

hope this helps

 

[67CBodyGuy]

I strongly recommend that anyone who thinks the "ammeter bypass" actually accomplishes anything should watch several of the youtube video's made by @72RoadRunnerGTX regarding the ammeter bypass. He explains why the bypass has practically no value and introduces new vulnerabilities to the electrical system, and he explains the likely reasons why this bypass originated (ie when and for what vehicles, which are not our cars).



I think he's made about 6 videos on this topic, covering this topic from every angle.

 

[67Dart273]

I strongly recommend that anyone who thinks the "ammeter bypass" actually accomplishes anything should watch several of the youtube video's made by @72RoadRunnerGTX regarding the ammeter bypass. He explains why the bypass has practically no value and introduces new vulnerabilities to the electrical system, and he explains the likely reasons why this bypass originated (ie when and for what vehicles, which are not our cars).



I think he's made about 6 videos on this topic, covering this topic from every angle.

Well it IS in fact a VERY REAL problem, and is made worse by any added modern "stuff" like big radios (amps) electric pumps and whatever else, alone with larger alternators.

MA KNEW THIS WAS A PROBLEM which is why the so called police/ taxi/ fleet option exits. IT IS IN FACT a bulkead bypass at least in some partial measure.

And being the owner of a sea barge, YOU should know that even back around 71-ish, Ma abandoned the "full current' ammeter and went with an external shunt setup.

As a person who performed HVAC/R install, maintenance and repairs for about a dozen years, I've replaced many of the same general type of 1/4 "flag" connector terminals in heat pumps regarding the electric heating elements. Those terminals, in an electric furnace, handle nominally 20-25A for a standard 5KW heating element, AND THEY FAIL.

So those bulkhead terminals ARE IN FACT out of design spec at the outset.

HOWEVER most of us have quit recommending the specific bypass method shown on the MAD site, but rather REPAIR the bulkhead or run wiring STRAIGHT THROUGH, eliminate the AMMETER, and then run a LARGE GAUGE fused or breaker protected bypass direct from the alternator to the battery.

IF YOU DO NOT UNDERSTAND the WEAKNESSES of the factory full current ammeter, you are simply in a dream world of denial.


I myself had to pull the cluster out of my 70 RR way WAY back in the early 70's, and drilled out and ran larger wires through the bulkhead to replace damaged terminals. This, obviously was LONG before Al Gore invented the internet.

WHY DO AMMETERS DIE?

Simple, really. The "shunt" which is really the entirety of the working "guts" of the ammeter--except for the needle, ---is NOT CRIMPED, welded, or brazed to the studs. The studs are generally splined, but they depend on hard mechanical clamping. In the case of my old 70RR (440-6, Ralleye dash) the cluster was PLASTIC, so the "sandwich" of the shunt, the studs, the plastic cluster housing, washers, and nuts, at some point got warm enough from TOO MUCH CURRENT that everything started to warm, soften the plastic, and become LOOSE. Now you have HOT, and you have HOT plastic, and you have SMELL and sometimes worse.

THIS IS ALL WELL DOCUMENTED I don't give one twit what your buddy on YeweToobe claims.

 

[Mattax]

I've posted this a bunch of times because this crazy magic bullet type advice can be very destructive. While there have been times when an ammeter has failed, in those instances there is a cause - usually some sort of environmental damage (water leak), or excessive charging rate, or modifications (add ons like a winch, EFI and electric fans and pumps, or high watt stereo amplifier).

In the meantime, lots of innocent people hack up their car's wiring and cause real damage.


We've had at least two people post that when they, or their dad, with many years working service at Chrysler dealerships never encountered this supposed massive ammeter fireball problem. Here's one please remove

Sometime ago I snipped a bunch of posts from threads on the IFSJA (full size Jeep) forum to show where people got themselves in trouble following various ammeter delete ideas. See them here 15V

The ammeter is very useful to monitor battery charging - especially after a jump start. It is not the same as having a voltmeter. A voltmeter is also useful. They do not show the same thing. Learning to use both is very powerful.

 

[Mattax]

Good evening everyone.

So, 66 Barracuda is not charging. I went to do the ammeter bypass. Hooked a line to the alternator(back wire /green wire). Black wire and the other side i hooked to the starter relay lug on the firewall. Immediately the motor started to take off on me when I put the battery back on. What did I do wrong?

You followed bad advice.
Lets move on.

First. What do you mean by 'not charging'?
If the ammeter is showing discharge while driving, then the alternator circuit is not providing power.
If the ammeter is showing no charge while driving (needle straight up), everything is normal.

The ammeter is in the battery feed/charge line to the main splice.
Heavy (12 gage) black wire to the firewall is power feed from the alternator.

Notice the power from the alternator does not go through the ammeter except when the battery needs to be recharged.

Bypassing the ammeter leaves you blind. So if there is no damage, connect it back up. Make sure no bare conductor touches ground metal. Depending the instrument panel, there very well may have been insulating washers used. All of theose wires are connected to the battery positive and the only protection from a short is that fusible link.

You can look at the firewall connections for damage. However a failure in the alternator circuit is probably something more basic. A bad connection or failure in the alternator or regulator.

 

[Professor Fate]

However a failure in the alternator circuit is probably something more basic. A bad connection or failure in the alternator or regulator.

And don't forget that grounds are also a "connection"- make sure all your grounds (esp. including the VR case) have a good solid ground to bare metal; no paint or corrosion in the connections.
And depending on how the vehicle is equipped, and with what parts; you could have mismatched components. Especially with a '66: for example, a later dual field alternator- usually all that you can get as replacements for the early single field units- are not correctly modified or the second field is not properly grounded.
A better description of the vehicle and any replacement parts and/or modifications already made is in order.

 

[72RoadRunnerGTX]

Well it IS in fact a VERY REAL problem, and is made worse by any added modern "stuff" like big radios (amps) electric pumps and whatever else, alone with larger alternators.

MA KNEW THIS WAS A PROBLEM which is why the so called police/ taxi/ fleet option exits. IT IS IN FACT a bulkead bypass at least in some partial measure.

And being the owner of a sea barge, YOU should know that even back around 71-ish, Ma abandoned the "full current' ammeter and went with an external shunt setup.

As a person who performed HVAC/R install, maintenance and repairs for about a dozen years, I've replaced many of the same general type of 1/4 "flag" connector terminals in heat pumps regarding the electric heating elements. Those terminals, in an electric furnace, handle nominally 20-25A for a standard 5KW heating element, AND THEY FAIL.

So those bulkhead terminals ARE IN FACT out of design spec at the outset.

HOWEVER most of us have quit recommending the specific bypass method shown on the MAD site, but rather REPAIR the bulkhead or run wiring STRAIGHT THROUGH, eliminate the AMMETER, and then run a LARGE GAUGE fused or breaker protected bypass direct from the alternator to the battery.

IF YOU DO NOT UNDERSTAND the WEAKNESSES of the factory full current ammeter, you are simply in a dream world of denial.


I myself had to pull the cluster out of my 70 RR way WAY back in the early 70's, and drilled out and ran larger wires through the bulkhead to replace damaged terminals. This, obviously was LONG before Al Gore invented the internet.

WHY DO AMMETERS DIE?

Simple, really. The "shunt" which is really the entirety of the working "guts" of the ammeter--except for the needle, ---is NOT CRIMPED, welded, or brazed to the studs. The studs are generally splined, but they depend on hard mechanical clamping. In the case of my old 70RR (440-6, Ralleye dash) the cluster was PLASTIC, so the "sandwich" of the shunt, the studs, the plastic cluster housing, washers, and nuts, at some point got warm enough from TOO MUCH CURRENT that everything started to warm, soften the plastic, and become LOOSE. Now you have HOT, and you have HOT plastic, and you have SMELL and sometimes worse.

THIS IS ALL WELL DOCUMENTED I don't give one twit what your buddy on YeweToobe claims.

Thanks, some valid points here, and one not so much, very dangerous in fact. The factory “fleet bypass”, C body recall bypass, and ammeter construction are all covered in detail in those videos mentioned. Closing in on about 50 years in the trade myself, many at the dealers back in the day. I do understand the weaknesses and the design intent of this original electrical system.

 

[kewen300]

You followed bad advice.
Lets move on.

First. What do you mean by 'not charging'?
If the ammeter is showing discharge while driving, then the alternator circuit is not providing power.
If the ammeter is showing no charge while driving (needle straight up), everything is normal.

The ammeter is in the battery feed/charge line to the main splice.
Heavy (12 gage) black wire to the firewall is power feed from the alternator.
View attachment 1716410652
Notice the power from the alternator does not go through the ammeter except when the battery needs to be recharged.

Bypassing the ammeter leaves you blind. So if there is no damage, connect it back up. Make sure no bare conductor touches ground metal. Depending the instrument panel, there very well may have been insulating washers used. All of theose wires are connected to the battery positive and the only protection from a short is that fusible link.

You can look at the firewall connections for damage. However a failure in the alternator circuit is probably something more basic. A bad connection or failure in the alternator or regulator.

One of this first things I did was put a new voltage regulator in it. I have power to everything however the battery does not charge. The motor is a 360 that has been built to a 408. Electronic ignition. No points. Automatic transmission. The only thing that I have added was a retrosound head unit radio. A replacement main dash speaker and 2 small kicker speakers under the dash on either side. For the power leg I tapped into the red leg going to the ignition so it will shut off when the car turns off. I have the same voltage at the battery and starter relay, had power going to the regulator when key in run position. I had roughly the same voltage at each lug of the ammeter. The alternator appeared to be putting out power. However with the engine running one thing I did notice was with the alternator the power was jumping all.over the place. One spot it'd read 13 then it'd drop to 3 for half a second then come back up. Only constant was power on the battery terminals because it wasn't charging just draining. I plan to do more diag when I get home later.

 

[kewen300]

One of this first things I did was put a new voltage regulator in it. I have power to everything however the battery does not charge. The motor is a 360 that has been built to a 408. Electronic ignition. No points. Automatic transmission. The only thing that I have added was a retrosound head unit radio. A replacement main dash speaker and 2 small kicker speakers under the dash on either side. For the power leg I tapped into the red leg going to the ignition so it will shut off when the car turns off. I have the same voltage at the battery and starter relay, had power going to the regulator when key in run position. I had roughly the same voltage at each lug of the ammeter. The alternator appeared to be putting out power. However with the engine running one thing I did notice was with the alternator the power was jumping all.over the place. One spot it'd read 13 then it'd drop to 3 for half a second then come back up. Only constant was power on the battery terminals because it wasn't charging just draining. I plan to do more diag when I get home later.

This voltage regulator that i installed was a Standard Ignition 12v 15 amp part number STD vr101

 

[Mattax]

What did the ammeter show?

 

[Mattax]

First. What do you mean by 'not charging'?

The only way to know if the battery is charging is with an ammeter.

But its common for people to use the term charging as a way of saying the alternator not working or working. That's fine in some situations but in this situation it confuses things.

For the power leg I tapped into the red leg going to the ignition so it will shut off when the car turns off.

It will not shut off with the key.
Go back and redraw your diagram. It should look the similar to the diagram I posted above. The J1 wire is the feed to the ignition switch. Follow it back to the battery positive post. Q3 to the fuse box, same thing.

However with the engine running one thing I did notice was with the alternator the power was jumping all.over the place. One spot it'd read 13 then it'd drop to 3 for half a second then come back up. Only constant was power on the battery terminals because it wasn't charging just draining. I plan to do more diag when I get home later.

if you read voltage in different locations along a current path, it will show the voltage at each of those points. If the voltage is lower at a downstream point, then there was resistance in between the two locations. Voltage difference = Current x Resistance.

I had roughly the same voltage at each lug of the ammeter.

Shouldn't be any voltage drop across the ammeter. It's just a big plate with two studs pressed in. Unless the studs get loose or there is corrossion, there is no reisistance to speak of.

 

[Oldmanmopar]

Well Not reading all the BS here is what I know is a fact. The black wire and the red wire that go to the amp meter. I have always connected the two behind the dash when needing the start the car with the cluster out.

That is bypassing the amp gauge and it still charges because the car will run without the battery connected after starting it.

What would be the difference doing it under the hood instead of under the dash. Still a bypass