Ammeter bypass (or whatever you call it)

[bcOH67]

Been trying to read into this as I’m rewiring things and I’ve seen different posts on this but still don’t have a clear idea…

All that I have to do is create a wire that goes from the alt stud to the starter relay, and things are ‘safer’? It’s been running fine as is, I’m just rewiring things to clean it up. I figured I’d do it now if just making one wire is all I have to do. If it’s more involved than that I’ll just leave it alone for now. Not worried about the gauge being accurate.

 

[493 Mike]

Been trying to read into this as I’m rewiring things and I’ve seen different posts on this but still don’t have a clear idea…

All that I have to do is create a wire that goes from the alt stud to the starter relay, and things are ‘safer’? It’s been running fine as is, I’m just rewiring things to clean it up. I figured I’d do it now if just making one wire is all I have to do. If it’s more involved than that I’ll just leave it alone for now. Not worried about the gauge being accurate.

All the current from the alternator passes through the contacts at the bulkhead connector. As the brass wire terminals in the connector age/corrode/become loose from vibration, they become more resistant to electricity flow and that causes heat. With enough heat the connector can melt/fires can start and your happiness leaves the room! It is a basic design flaw. Since the wires to the amp gauge also feed current to operate interior accessories a connection is necessary to feed current to the bypassed amp gauge. I suggest bolting the gauge wire terminals together along with a feed wire from the relay stud to provide operating power. Both the new alternator to relay stud and the stud to amp gauge power supply cables should be protected with fuses or fusible link. Install a voltmeter or have your old amp gauge converted to a voltmeter operation. Of course this will require another wire from the starter relay stud and a ground connection.
Mike

 

[Nacho-RT74]

Bulkhead conections are not affected just by the dust, grease, oil… environmental conditions on engine bay, but also by its own limits. Packard terminals get its own current limits still being new, so with the unneficiency of the factory alts at iddle which makes a constant charge stage when revving up. This stage is what keeps going over the packard conection limits, which is of course getting worst with the mentioned environment conditions over the years.

Saving the iddle charge capacity will keep safer all the charging system, ammeter and even the bulkhead. With a good iddle alt capacity just the load requested by the car will be going throught these conections saving from battery charge added load.

So, upgrading alt will keep safe the amm and even the bulkhead connections on a regular factory designed loads. But is true the firewall paths upgrade is better. But don’t get worried about amm itself.

 

[hunt2elk]

Catalog
Here is some reading material for you on the subject. In this rewire, the amp gauge is eliminated and replaced with a volt meter. Nacho has another variation which keeps the stock ammeter.

 

[threewood]

I've never seen an ammeter fail. If you look at the gauge itself there is no failure point....except the gasket can be crushed from overtightening.

The biggest failure point is the bulkhead connector. Connections get loose, cause high resistance and then melt or burn.

 

[4406bbl]

I've never seen an ammeter fail. If you look at the gauge itself there is no failure point....except the gasket can be crushed from overtightening.

The biggest failure point is the bulkhead connector. Connections get loose, cause high resistance and then melt or burn.

Well the problem is they do, especially dodge trucks, they corrode internally where the stud is pressed into the brass straps and gets worse when somebody just throws a wrench on the nuts and cranks them down bending things inside the gauge. Always a wrench on each nut when you tighten the leads on the back of the ammeter.

 

[4406bbl]

Been trying to read into this as I’m rewiring things and I’ve seen different posts on this but still don’t have a clear idea…

All that I have to do is create a wire that goes from the alt stud to the starter relay, and things are ‘safer’? It’s been running fine as is, I’m just rewiring things to clean it up. I figured I’d do it now if just making one wire is all I have to do. If it’s more involved than that I’ll just leave it alone for now. Not worried about the gauge being accurate.

This will help, make sure the ammeter leads are tight using 2 wrenches, check and clean the bulkhead connector, fuse or fuse link the new lead you add between the alternator and battery, and hooking any new accessories to that lead, not in the car will go a long way to avoid new problems.

 

[Sinitro]

Biggest issue with the bulkhead connectors(0.25" tab) is that their internal contact tension loosens with age...
Next due to weakening contact they heat up increasing their resistance and oxidation buildup.
As the oxidation builds their connections become poor and corrupted.
A good maintance tip is to pull apart the connectors, tighten up the female side and burnish the male side, coat with dia-electric grease.
Reinstall, now good to go..

Just my $0.02..

 

[72RoadrunnerGTX]

Been trying to read into this as I’m rewiring things and I’ve seen different posts on this but still don’t have a clear idea…

All that I have to do is create a wire that goes from the alt stud to the starter relay, and things are ‘safer’? It’s been running fine as is, I’m just rewiring things to clean it up. I figured I’d do it now if just making one wire is all I have to do. If it’s more involved than that I’ll just leave it alone for now. Not worried about the gauge being accurate.

If you feel the need to by-pass something, by-pass the charging circuit Packard connectors in the bulkhead connector, the weakest link in the original charging system. Check the connections at the ammeter and leave it alone. The described alternator to battery by-pass will defeat the purpose and function of the ammeter. No added loads at the battery.

Can’t compare the later Dodge truck plastic ammeter issues with these passenger car ammeters, different construction altogether.

 

[4406bbl]

If you feel the need to by-pass something, by-pass the charging circuit Packard connectors in the bulkhead connector, the weakest link in the original charging system. Check the connections at the ammeter and leave it alone. The described alternator to battery by-pass will defeat the purpose and function of the ammeter. No added loads at the battery.

Can’t compare the later Dodge truck plastic ammeter issues with these passenger car ammeters, different construction altogether.

I disagree on the ammeter, my ammeter in my 70 is constructed exactly the same as my 75 truck, studs pushed thru a strap. That connection can get loose and cause heat, just reaching g up behind a dash with a wrench and tightening it is a bad idea, 2 wrenches so you do not stress the connection. The only thing plastic on a truck is the housing the gauge mounts in. The OP said he does not care if the ammeter works. A strapped ammeter and a bypass between the battery and alternator is a way safer install, especially when the old battery gets a shorted or dead cell, and the alternator gets full fielded or shorted, or the field circuit develops high resistance so it just keeps charging. One other issue is most reman alternators are 60 amp, not the 37 most non ac cars had. Nothing wrong with bypassing the bulkhead either. Doing everything keeps the fire under the hood. To make it even safer the blue wire at the regulator should be controlled by a relay and connected directly to the battery so bad connections do not cause overcharging.

 

[72RoadrunnerGTX]

I disagree on the ammeter, my ammeter in my 70 is constructed exactly the same as my 75 truck, studs pushed thru a strap. That connection can get loose and cause heat, just reaching g up behind a dash with a wrench and tightening it is a bad idea, 2 wrenches so you do not stress the connection. The only thing plastic on a truck is the housing the gauge mounts in. The OP said he does not care if the ammeter works. A strapped ammeter and a bypass between the battery and alternator is a way safer install, especially when the old battery gets a shorted or dead cell, and the alternator gets full fielded or shorted, or the field circuit develops high resistance so it just keeps charging. One other issue is most reman alternators are 60 amp, not the 37 most non ac cars had. Nothing wrong with bypassing the bulkhead either. Doing everything keeps the fire under the hood. To make it even safer the blue wire at the regulator should be controlled by a relay and connected directly to the battery so bad connections do not cause overcharging.

The referenced difference in construction is exactly the plastic cluster frame of the trucks and the pot metal cluster frames of the passenger cars, as referenced in the Mad Electrical article. The plastic being much less tolerant of any heat generated by resistance at the stud head to ammeter bus connection and contributing to further resistance caused heat. The more the plastic softens up the more tension is released at the stud head, more resistance and heat, chain reaction. Plus, the fact that trucks tended to have more mis-placed loads at the battery than cars at that time, (wenches, aux lighting, and more) over-stressing the entire charging system, placing the ammeter and its connection well outside of its design limits. A little solder at the stud head to bus connection will remove any tension release from causing a resistance/heat problem.

The field relay suggested addresses over-voltage caused by voltage drop between the regulator reference and the battery, common problem on these cars. In itself is not going force a high charge current rate alone.

 

[4406bbl]

I give up....the fiber insulators can do the same thing. When an idiot tightens the ammeter nuts without holding the nut behind the terminal it twists the shunt. The stud is swaged in and this action loosens it. That is all. Plastic or metal it will heat up and fail. Can we just agree it is a bad design, especially when a bigger alternator is installed and the battery fails. The OP wants to make it safer, I told him how to do it, I will also add that a new fresh battery without issues is probably the most important, not some junk battery because they do not drive the car much.

 

[72RoadrunnerGTX]

I give up....the fiber insulators can do the same thing. When an idiot tightens the ammeter nuts without holding the nut behind the terminal it twists the shunt. The stud is swaged in and this action loosens it. That is all. Plastic or metal it will heat up and fail. Can we just agree it is a bad design, especially when a bigger alternator is installed and the battery fails. The OP wants to make it safer, I told him how to do it, I will also add that a new fresh battery without issues is probably the most important, not some junk battery because they do not drive the car much.

Did you watch the video? We agree on more than you think. Yes, abuse at the terminals is a common cause of ammeter connection failures. Yes, overtightening of the mounting nuts can crush/damage the fiber board insulators leading to loose/high resistance connections. Yes, twisting the stud will damage the stud head to bus connection. No, I don’t agree it is “a bad design” when operated within its original design limits, well maintained connections, and with all operational loading correctly placed on the alternator side of the ammeter as are all factory operating loads.

The plastic cluster framed truck ammeter suffered heat related damage at a much higher rate than any pot metal framed clusters, big difference.
The Packard connectors at the bulkhead are the weakest link in the original system by far.

 

[RJ Squirrel]

Good reading guys and good timing on this subject. I have all my wiring and dash on the bench right now. I have removed the ammeter shunt and replaced the gauge with a voltmeter. I am installing relays for the headlights, power for the headlights is the "relay feed" on the starter relay stud. The old headlight wiring is now just relay triggers. I deleted/removed the old red wire from the ammeter that returned to the starter relay stud thru the bulkhead connector, ran the alt B lead directly to the starter relay stud, and then fed the black wire positive lead that powers everything else in the car from the same starter relay stud, so essentially the starter relay stud is my "positive bus" in front of the firewall. I will need to connect the horn relay there too and add fuses for it and the headlights. The black positive feeder wire will pass through the firewall with a single heavy duty bulkhead connector, not the original little 1/4" tab connector. Hope this makes sense, and please let me know if anyone sees any flaws in this plan!
And as always thank you all for the wealth of information from this forum.

 

[4406bbl]

Did you watch the video? We agree on more than you think. Yes, abuse at the terminals is a common cause of ammeter connection failures. Yes, overtightening of the mounting nuts can crush/damage the fiber board insulators leading to loose/high resistance connections. Yes, twisting the stud will damage the stud head to bus connection. No, I don’t agree it is “a bad design” when operated within its original design limits, well maintained connections, and with all operational loading correctly placed on the alternator side of the ammeter as are all factory operating loads.

The plastic cluster framed truck ammeter suffered heat related damage at a much higher rate than any pot metal framed clusters, big difference.
The Packard connectors at the bulkhead are the weakest link in the original system by far.

We do agree, the problem is the alternators now availiable are almost always past the design limits. All I know is my plastic gauged 4x4 has made it 40 years since I had the dash out and 120k miles, snow plow, a/c, trailer tow, 100 amp at idle alternator with nothing more than tightening every connection and a 2 gauge wire between the alternator and battery. All added accessories and the a/c blower are hooked directly to the battery. The alt to battery wire flat works taking into account the average guy just buys new parts and does not realize he could have a problem.

 

[Sinitro]

One thing I have done...
Is to run a 2nd alternator output lead bypassing the bulkhead connectors...
This helps to ease its load...

Just my $0.02...

 

[Nacho-RT74]

One thing I have done...
Is to run a 2nd alternator output lead bypassing the bulkhead connectors...
This helps to ease its load...

Just my $0.02...

+1

 

[Nacho-RT74]

We do agree, the problem is the alternators now availiable are almost always past the design limits. All I know is my plastic gauged 4x4 has made it 40 years since I had the dash out and 120k miles, snow plow, a/c, trailer tow, 100 amp at idle alternator with nothing more than tightening every connection and a 2 gauge wire between the alternator and battery. All added accessories and the a/c blower are hooked directly to the battery. The alt to battery wire flat works taking into account the average guy just buys new parts and does not realize he could have a problem.

Alternator do not past the original design limits by itself, but the devices added.

You can get a 500 amps iddle capacity alt, but if the car sucks 25, the alt will just put those 25 amps out.

If the batt got discharged then this discharge rate will be added to the 25 amps demand on the charging stage for a while the batt still requires the load to get fully charged back. Nothing more, nothing less. This is the load running throught the amm, but not the 25 amps.

So if you source accs on batt, this load will be read by the amm like charging, which is not just a wrong reading, but also an unnecesary overstress into the gauge.

Sure some devices still will need to be sourced straight from batt, like the starter motor, but these use to be the higher rates ones but just momentary… like a winch on trucks

 

[Kern Dog]

Here is the reroute as suggested by MAD enterprises....

 

[72RoadrunnerGTX]

One thing I have done...
Is to run a 2nd alternator output lead bypassing the bulkhead connectors...
This helps to ease its load...

Just my $0.02...

That sounds an awful lot like C-body recall 48549 from the early seventies.