Ammeter to Voltmeter Conversion -- Existing Wire Question

[72RoadrunnerGTX]

Our C-Body brethren have a thread or 2 on this going as well. This guy has an interesting approach for an "under hood bypass" to remove 50% of the load from the ammeter circuit. He also spells out a full bypass later in the thread for those that were wanting that.

https://www.forcbodiesonly.com/mopar-forum/threads/underhood-ammeter-bypass.55911/

Direct link for his "Simple Bulkhead Bypass"

https://www.forcbodiesonly.com/mopar-forum/threads/simple-bulkhead-bypass.56391/

Yea, every forum has much of the same, similar, threads as here on this topic, “We all know the ammeter is the Achilles heels of old Mopars…”, 9-pages pages of opinions, misinformation, and incorrect assumptions. Verry little fact-based information presented. Did see a few posts on the factory fleet production bulkhead by-pass approach.

 

[72RoadrunnerGTX]

So I keep forgetting to ask this — if you have a lower output alternator say 45-60 amps vs 90 or higher, does the lower alternator prevent too much current/overload? Basically I understand a higher output amp will power only as much as you need but does a lower amp alternator prevent too much load to keep in line with original wiring requirements?

The potential total current flow in the charging circuit is determined by the total vehicle loads. Nothing to do with the total output current capacity of a given alternator. The advantage of running a higher than stock rated alternator with stock loads is that it can produce more output capacity at lower rpms(idle) than the lower current stock rated alts. While running, any current load the alternator can’t keep up with is drawn from the battery (discharge), just over stresses the ammeter-battery side of the charge circuit more than it needs to be.

 

[mrmolding]

The potential total current flow in the charging circuit is determined by the total vehicle loads. Nothing to do with the total output current capacity of a given alternator. The advantage of running a higher than stock rated alternator with stock loads is that it can produce more output capacity at lower rpms(idle) than the lower current stock rated alts. While running, any current load the alternator can’t keep up with is draw from the battery (discharge), just over stresses the ammeter-battery side of the charge circuit more than it needs to be.

Great! Thanks!

 

[Nacho-RT74]

Actually I'd say overstresses the alt-amm side of the wiring mor. It uses to be the first it gets burnt/melted by the batt charge load added to the already stressing side of the charging circuit to feed the car demands.

 

[Don67Satellite]

From a 1999 edition of Mopar Action. Well written interesting read.

https://www.allpar.com/threads/taking-charge-tips-and-tweaks-to-keep-your-mopar-current.237043/

 

[72RoadrunnerGTX]

Actually I'd say overstresses the alt-amm side of the wiring mor. It uses to be the first it gets burnt/melted by the batt charge load added to the already stressing side of the charging circuit to feed the car demands.

Technically, it’s everything from splice 1 to the battery takes on more current stress from under rated alternators, includes both ammeter terminals equally. Was trying to keep it simple.

 

[72RoadrunnerGTX]

From a 1999 edition of Mopar Action. Well written interesting read.

https://www.allpar.com/threads/taking-charge-tips-and-tweaks-to-keep-your-mopar-current.237043/

Agreed, although being a bit dated now concerning options available now, Mr. Ehrenberg’s writings are generally more fact based and absent the close to hysteretic exaggerations/misinformation common in these published articles on this subject.

 

[Don67Satellite]

Agreed, although being a bit dated now concerning options available now, Mr. Ehrenberg’s writings are generally more fact based and absent the close to hysteretic exaggerations/misinformation common in these published articles on this subject.

I would agree a bit dated but still relevant. The original C-Body thread I linked was about this exact method. The author credits Ehrenberg. He just does a step by step explanation with photographs for the less electrically inclined.

 

[72RoadrunnerGTX]

Exact method, what am I missing? The OP (cbarge), and most of the responding posts, are mostly describing/discussing the engine compartment charge circuit by-pass, in this case adding a 12ga wire run from the alternator output stud to the starter relay. While this may alleviate some battery charging current through the original charge path, does nothing about the factory vehicle loads drawn from spice 1 still being sourced through the original alternator wire run and bulkhead connection and makes the ammeter accurately nonexistent. It’s little more than a band-aid fix. Did see where the OP credited an article by Mr. Ehrenburg on Mopar Action, could get the link to work, could it have been another article? Not seeing him promote such a method frankly.

The Ehrenberg article linked above describes complete bulkhead connector by-pass and wire upgrades, as the factory did in fleet production, that leaves a fully functional ammeter. Don’t see anything in the article about the band-aid fix described in the Cbodyonly thread.

 

[Don67Satellite]

Exact method, what am I missing? The OP (cbarge), and most of the responding posts, are mostly describing/discussing the engine compartment charge circuit by-pass, in this case adding a 12ga wire run from the alternator output stud to the starter relay. While this may alleviate some battery charging current through the original charge path, does nothing about the factory vehicle loads drawn from spice 1 still being sourced through the original alternator wire run and bulkhead connection and makes the ammeter accurately nonexistent. It’s little more than a band-aid fix. Did see where the OP credited an article by Mr. Ehrenburg on Mopar Action, could get the link to work, could it have been another article? Not seeing him promote such a method frankly.

The Ehrenberg article linked above describes complete bulkhead connector by-pass and wire upgrades, as the factory did in fleet production, that leaves a fully functional ammeter. Don’t see anything in the article about the band-aid fix described in the Cbodyonly thread.

Yes, Ehrenburg's article talks about how fleet vehicles had a factory Chrysler bulkhead bypass, eliminating the trouble spots, which he shows some photos of but then he goes into this:

4. To straighten out the wiring problem permanently,
you need some decent supplies. A few feet of automotive-grade wire, 10
or 12 gauge (depending on you alternator's rating and anticipated
current loading), fusible links (see text), some crimp splices and
heat-shrink tubing, and, if need be, some quality electrical tape. If
you're adding any other accessories, do yourself a favor and opt
for the modern blade-type fuse holder and fuses.

5. Connect a fusible link to the starter relay stud. Crimp-splice
in a piece of suitable (heavy-gauge) wire, and connect the other end to
the alternator stud. That's it....firewall problems bypassed
forever!

That's exactly what cbarge is doing in his photo tutorial IMHO. Not exactly sure what you read.

But anyways, the C-Body guys seem to have a far more coherent thread going about this subject than anything I've read here so far, so I'll bow out of the conversation.

 

[72RoadrunnerGTX]

Interesting, I do see that now, missed that, a bit surprised frankly. The information in that article is more outdated than I thought, defiantly not a permanent fix by any means. Ask any electrician, parallel conductor paths in any circuit are to be avoided like the plague.

BTW, there are just as many, if not more, comprehensive threads/debates on this subject here on this site as well. Some would say too many.

 

[Rebel74]

So the linked discussion proposes a "solution" that results in an ammeter that is no longer accurate... is there a solution that a) reduces the total current load through the ammeter itself and b) maintains an accurate ammeter reading? Is that even possible? Or would the ammeter have to be moved to the other side of the bulkhead?

I guess what I'm asking is, "Is there a way to place the ammeter's point-of-measurement on the other side of the firewall, while still being able to monitor the readout inside the cab?"

 

[Nacho-RT74]

is there a solution that a) reduces the total current load through the ammeter itself

Yes, as explained hundred of times, with an alt able to handle all the car and its accesories loads without require for the battery assistance

b) maintains an accurate ammeter reading? Is that even possible? Or would the ammeter have to be moved to the other side of the bulkhead?

I guess what I'm asking is, "Is there a way to place the ammeter's point-of-measurement on the other side of the firewall, while still being able to monitor the readout inside the cab?"

It can be anywhere between the main splice inside the cab and the starter relay stud which is being used as a junction point. It CAN'T be between batt and starter relay, because the load going throught starter relay to feed the starter motor solenoid could be more that the amm is able to handle... hence why that relay with the huge stud is being used. Aside there is no need to monitoring that load being just used at the cranking instant. You will read just what the alt is feeding to recharge the batt after the cranking load, which is less but gets longer into the time to recover that load lost/requested by the starter motor.

However, it makes no sense get gauge you can't read anytime being into engine bay, designed to warn you about your car loads status, batt charge/discharge status and alt operation... all these stages can change within seconds.

Technically, it’s everything from splice 1 to the battery takes on more current stress from under rated alternators, includes both ammeter terminals equally. Was trying to keep it simple.

I think you are not getting what I meant. While is true every load between splice and batt ( amm included ) can be relaxed with a good alt and stressed with under rated alts when reving up and getting back at iddle ( back and forth amm reading ), the section between alt and splice ( and specially affecting the bulkhead black wire conection ) gets MORE stress, because it will get no matter what the nominal car loads anytime... PLUS the recharging load if batt gets discharged and while you are revving up. Read carefully the reply #71 with the rude maths I made about that. For a while the section between splice and batt is not getting the full nominal car loads getting throught, still with an under rated alt... except with engine off of course.

After the splice, just the recharging load or the discharge load will be running throught that wire, but before the splice every single ampere will be running throught that section when recharging. Except, with engine off &/or un capacity from the alt of course.

Hence why I say an upgraded alt will get safer the system with just the amm-alt ( or splice ) wire upgrade or even STILL without upgrade the charging wiring ( IS NOT a recomendation of course ), because won't get more continuous discharge/charge stage. But if making an alt capacity upgrade it makes no sense get a full charging network upgrade incomplete.

 

[mrmolding]

The potential total current flow in the charging circuit is determined by the total vehicle loads. Nothing to do with the total output current capacity of a given alternator. The advantage of running a higher than stock rated alternator with stock loads is that it can produce more output capacity at lower rpms(idle) than the lower current stock rated alts. While running, any current load the alternator can’t keep up with is drawn from the battery (discharge), just over stresses the ammeter-battery side of the charge circuit more than it needs to be.

Ok, I know it's been a few weeks and everything made perfect sense a few weeks ago. But...
I got a Powermaster 7018 95 amp alternator after I got a Remy 50 amp that had a stripped pulley hole. Looked like a helicoil was poorly installed on the Remy reman unit. The Powermaster is beautiful compared to the reman unit.
But, on the Powermaster instructions it plainly says to use an 8 gauge charge wire. So I got sucked into the charge wire / voltmeter discussion again and I called Powermaster tech support. The tech (who sounded at least 50 or 60) told me that I needed a charge wire even with all new M&H wiring in place because the alt gauge and wiring could not handle the amps of the new alternator and that too much current would be flowing in the smaller factory sized wires.
I then told him that my forum experts told me that it would only draw what it needed and not overpower a stock setup but he told me that my car might burn to the ground with the 95 amp vs 37 amp stock unit.
I again told him that I had nothing extra and that I was fairly certain that my forum experts said I'd be fine. He said I'd be better off just adding a charge wire and disconnecting the alternator gauge to be safe.
At this point, I'm getting sucked into the confusion again and wondering if I did put the charge wire on, how would the ammeter read? Would it work at all, just a little bit in each direction?
Anyway, wanted to share!

 

[72RoadrunnerGTX]

Another reason I prefer Tuff Stuff. Again, at the risk of repeating myself here, simple explanation, with no change to the bone stock loads, heathy stock charge wiring and related connections, the alternator will not create additional charge/load current. All things being equal, the car is not going to burn down just because a higher output alternator was installed. That said, the weakest link in the original design is the bulkhead terminals in this circuit. I would at least bypass that connection, alternator swap or not, new wiring or not. If additional loads are to be installed, and more of this alternator potential current is utilized, I would/do up-size the charge circuit wiring.

 

[mrmolding]

Another reason I prefer Tuff Stuff. Again, at the risk of repeating myself here, simple explanation, with no change to the bone stock loads, heathy stock charge wiring and related connections, the alternator will not create additional charge/load current. All things being equal, the car is not going to burn down just because a higher output alternator was installed. That said, the weakest link in the original design is the bulkhead terminals in this circuit. I would at least bypass that connection, alternator swap or not, new wiring or not. If additional loads are to be installed, and more of this alternator potential current is utilized, I would/do up-size the charge circuit wiring.

Thanks! I appreciate the reconfirmation! I think it's easy to get sucked in especially when the condition of reman alternators is such junk. In the past five years, I've taken back two to NAPA and one to RockAuto due to stripped pulley threads. Eventually I got a good one. But the Powermaster is really nice. I'll try a Tuff Stuff next. Thanks again!

 

[Nacho-RT74]

8 gauge wire is necesary depending on several factors:

-Total car load demand
-battery reserve load capacity in case it get discharged.

Said this, if you note what kind of stuff your batt sources, is able to source the same the starter motor with a 4 or 2 gauge wire, than the brake pilot light on cluster with 16 gauge wire. So the load it doesn't slaves to to the source capacity but to the device to be feeded. Hence the wire gauge difference.

As I have "exampled" couple of times: your AC wall outlet feeds the same your cellphone charger than an iron or a hair dryer, and there is a HUGE DIFF on load between those devices. Everything is protected by a 10 or 15 amps circuit breaker in most of cases no matter the load capacity coming from the street because the load is a demand from the devices, not depending on the source capacity.

Once you get saved the poor iddle capacity, your batt will be safe from get discharged. When batt is discharged is one device more requesting for load. That's a load ( maybe 10 amps, or even 20 amps on regular conditions ) you will be saving from the charging circuit when you have an alt able to feed everything at the less sped as posible... ideally at iddle.

A Packard terminal setup is able to handle maybe 30 amps average ( with some occasionally peaks ) if clean and tight. If the car requires around 25-30 amps on regular conditions, bulkhead conection is about the limit. If batt gets discharged will request charge load... this adds the extra load the Packard terminal will be handling out of its limits, then heats floats on and... its consequences.

So as mentioned by 72RoadrunerGTX, No matter what alt or wire, the bulkhead is the wakest point.

Which is true is even if you still are not saving the bulkhead path, if you upgrade the alt capacity, since you are saving the batt discharge stage, THIS LOAD will be maybe 90% out of the game, so in opposition to the crowd believing, a higher output alt is SAFER to all the charging system, still on stock form than keep the low alt capacity.

Need to note I'm not saying you don't need to save the bulkhead path ( or upgrade the wire with 10 or 8 gauge thickness ), BUT just still with this weak spot present, when you leave the batt out of the game you will be reducing the total load on circuitry to recharge it at the discharge stage, because the discharge stage won't float on with the regularity it happens with stock alt. This mean the bulkhead will survive better too. Still around its limits, but not constantly over its limits, which made them to burn on most of our Mopars.

 

[mrmolding]

8 gauge wire is necesary depending on several factors:

-Total car load demand
-battery reserve load capacity in case it get discharged.

Said this, if you note what kind of stuff your batt sources, is able to source the same the starter motor with a 4 or 2 gauge wire, than the brake pilot light on cluster with 16 gauge wire. So the load it doesn't slaves to to the source capacity but to the device to be feeded. Hence the wire gauge difference.

As I have "exampled" couple of times: your AC wall outlet feeds the same your cellphone charger than an iron or a hair dryer, and there is a HUGE DIFF on load between those devices. Everything is protected by a 10 or 15 amps circuit breaker in most of cases no matter the load capacity coming from the street because the load is a demand from the devices, not depending on the source capacity.

Once you get saved the poor iddle capacity, your batt will be safe from get discharged. When batt is discharged is one device more requesting for load. That's a load ( maybe 10 amps, or even 20 amps on regular conditions ) you will be saving from the charging circuit when you have an alt able to feed everything at the less sped as posible... ideally at iddle.

A Packard terminal setup is able to handle maybe 30 amps average ( with some occasionally peaks ) if clean and tight. If the car requires around 25-30 amps on regular conditions, bulkhead conection is about the limit. If batt gets discharged will request charge load... this adds the extra load the Packard terminal will be handling out of its limits, then heats floats on and... its consequences.

So as mentioned by 72RoadrunerGTX, No matter what alt or wire, the bulkhead is the wakest point.

Which is true is even if you still are not saving the bulkhead path, if you upgrade the alt capacity, since you are saving the batt discharge stage, THIS LOAD will be maybe 90% out of the game, so in opposition to the crowd believing, a higher output alt is SAFER to all the charging system, still on stock form than keep the low alt capacity

Thanks! I appreciate the explanation! Makes a lot of sense. Thanks again!

 

[Nacho-RT74]

Thanks! I appreciate the explanation! Makes a lot of sense. Thanks again!

I think I was editing the reply while you quoted me adding more info based on my personal experiences. So check it out.

 

[mrmolding]

I think I was editing the reply while you quoted me adding more info based on my personal experiences. So check it out.

Yup. Just read the additional comment. Makes great sense again.
So, I have all new M&H stock wiring, just an aftermarket radio with no power amp, and with a 95 Amp Powermaster I do not need a charge wire and I can leave the ammeter in place. That is what I've wanted to do but most have seemed to have taken the voltmeter path these days. I have had 10 mopars and most were at least 15 years old when I started driving them. I ran out of gas, had many overheating issues, but never an electrical fire. Hoping to just reset my 70 Road Runner to new and enjoy it. Thanks again!