Circuit Protection and the "Shunt wire" by-pass

[Sinitro]

The Mopar OE wiring system has many weaknesses...
If the OE alternator and associated wiring is not updated whenever certain accessories are added,
such as electric fans, subwoofer/amplifier, electric fuel pump, electronic ignition. The major issues are the limited wiring size, typically 12AWG
and the 0.25" tab connectors used in the bulkhead/connecting block, at best they can only handle up to 25-30amps...

Just my $0.02...

 

[72RoadrunnerGTX]

Agreed, for the as original, original loads, and unaltered electrical system, the use of Packard terminals in the charge path at the bulkhead connector is by far the weakest link. Followed close behind by the factory bean counters approach to wire sizing. Aftermarket add-on loads aside, it’s all the stock 12 ga unfused wiring that is at greatest risk by installing this “Shunt wire” by-pass. Does not make anything about this electrical system safer by any means, makes it much less safe in fact.

 

[72RoadrunnerGTX]

Load testing this "Shunt wire" underhood by-pass, Safer?

 

[RJRENTON]

Load testing this "Shunt wire" underhood by-pass, Safer?

EXPERTLY DEMONSTRATED AND EXPLAINED.....complete with thermal readings.....and to those that still do not understand the ramifications of said "shunt by pass wire"....play the video again and listen to the gentleman......his demonstrations and explanations should teach the "self proclaimed experts" how things work and the consequences. I personally commend the author....he should copyright his presentation......THANK YOU for your outstanding effort.......best regards......
BOB RENTON

 

[Bb69gts]

Thanks. Learned something about the risk of running the extra “Blackwire” from the Alt.
Any criticism of converting ammeter to Volt meter? Best method of locking the red and black wires together?

 

[72RoadrunnerGTX]

Thanks. Learned something about the risk of running the extra “Blackwire” from the Alt.
Any criticism of converting ammeter to Volt meter? Best method of locking the red and black wires together?

Criticism for converting an ammeter to a voltmeter? Only for those who publicly promote the need to do so based on misinformation, ignorance of how this system works, or have to create a false pretense to sell the idea that if you don’t make the conversion you will be left on the side of the road or your Mopar will burn to the ground, the ammeter spontaneously combusting for no reason whatsoever. Is the ammeter the biggest threat/problem to this system in an original configuration? No.

Are there non-stock heavily modified electrical needs in some cases (i.e. restomods) that the stock ammeter is not well suited for? Definitely.

As far the best way to connect the ammeter wires together, as pictured in the video, bolt them together, insolate well. What do you gain by doing this only? Nothing really. Still have the weakest link, the Packard connections in the bulkhead to deal with and still have the charge circuit wiring in the dash. Some say just put both wires on one ammeter stud. Changes nothing, ammeter function is then disabled but leaves the ammeter terminals still energized.

 

[65CopCar]

Many current production cars have no method of fusing the alternator hot side. Easy enough to do with a Mega fuse. .
Doug

I personally like the MIDI fuse for the alternator circuit. Leave the MEGA fuse for the main circuit. Just be cognizant of the fuse curves and be aware of required temperature de-rating when choosing your amp size.

I mounted the MIDI fuse on the back of the alternator and added one at the battery. I think I ended up with a 90 amp - picture shows a 60 amp because I was awaiting for the 90 to show up.

 

[451Mopar]

What is the fuse at the alternator protecting?
If the alternator output wiring is sized to handle all the alternator output, then a fuse at the battery side should be all that is needed?
If powering multiple loads at the alternator, and the supply wires are small, they will burn before the 90 Amp fuse can protect them, assuming the battery wire is on the unfused side of the alternator.
Caution on moving additional loads to the alternator output to only turn them on when the engine is running. Having the loads on with the engine off, all the power will be through the battery to alternator circuit.

 

[65CopCar]

What is the fuse at the alternator protecting?
If the alternator output wiring is sized to handle all the alternator output, then a fuse at the battery side should be all that is needed?
If powering multiple loads at the alternator, and the supply wires are small, they will burn before the 90 Amp fuse can protect them, assuming the battery wire is on the unfused side of the alternator.
Caution on moving additional loads to the alternator output to only turn them on when the engine is running. Having the loads on with the engine off, all the power will be through the battery to alternator circuit.

Say your alternator wire gets pinched in the middle of the wire for whatever reason. Fused at the battery. Battery fuse opens up. The fault continues to be fed by the alternator. Granted not as much energy available from the alternator than the battery, but still a bunch of energy. That's why you fuse both ends.

You need a protection scheme. The small wires need to be adequately protected. A big wire in a fault condition can cause a lot more damage than a small wire that may act like a fuse and open up. You really need to sit down, draw the circuit out, and develop a protection scheme.

 

[451Mopar]

Say your alternator wire gets pinched in the middle of the wire for whatever reason. Fused at the battery. Battery fuse opens up. The fault continues to be fed by the alternator. Granted not as much energy available from the alternator than the battery, but still a bunch of energy. That's why you fuse both ends.

You need a protection scheme. The small wires need to be adequately protected. A big wire in a fault condition can cause a lot more damage than a small wire that may act like a fuse and open up. You really need to sit down, draw the circuit out, and develop a protection scheme.

Thanks.
So if the output wire shorts in the center, the alternator fuse protects the Alternator or Wire depending on the size of the wire?
I was trying to say is a 90 Amp fuse for wires less than about 4 AWG, the wires will burn before the fuse.

 

[65CopCar]

I was trying to say is a 90 Amp fuse for wires less than about 4 AWG, the wires will burn before the fuse.

Not the case. There are many variables, but for starters are you using crap PVC insulation 85 deg C wire or XLPE 125 deg C wire? Of course if you are talking 12 AWG, you could have a problem on a 90 amp fuse.

The wires will actually take a lot of abuse. You really need to match the TCC from the fuse curves to match what you are trying to do. Depending on the the fuses used and the fault current, it is very easy to find a 90 amp fuse that clears before a 50 amp fuse would.

Also, I would suggest that you are trying to keep your car from burning down not protecting the wire. The wire can be replaced.

 

[Nacho-RT74]

Say your alternator wire gets pinched in the middle of the wire for whatever reason. Fused at the battery. Battery fuse opens up. The fault continues to be fed by the alternator. Granted not as much energy available from the alternator than the battery, but still a bunch of energy. That's why you fuse both ends.

You need a protection scheme. The small wires need to be adequately protected. A big wire in a fault condition can cause a lot more damage than a small wire that may act like a fuse and open up. You really need to sit down, draw the circuit out, and develop a protection scheme.

As soon the fuse link blows out by a heavy short on ANY section of the charging system, the engine will stall because the alt by itself is not able to hold a short, even less while short keeps sucking the power ign system requires. Regulator is on ign system network so at the same time will stop to feed the alt fields. So no need for fuse link on alt side…

The only source able to feed/keep alive a short where the fuse link enters in action is the batt. With or without engine running.

 

[nitro_rat]

Thanks. Learned something about the risk of running the extra “Blackwire” from the Alt.
Any criticism of converting ammeter to Volt meter? Best method of locking the red and black wires together?

I usually use a small brass machine screw and nut to lock the red and black wires together. Just wrap it securely with tape and/or heat shrink.

I use a cheap voltmeter from the auto parts store, tear it apart, and splice the movement into the factory cluster. The trick is to find one that sweeps the correct direction for your application.

This is the back of the cluster on a '68 Dart I did. I built my own solid state 5v voltage regulator (E-berg did an article on this in Mopar Action years ago but you can buy plug-and-play ones now) and took off power for the volt meter from there (small red and black wires running over to where the ammeter lugs were).

I glued the needle from the stock ammeter to the new movement with a drop of superglue:

I also put one of those solid state voltage regulators under the hood along with a properly protected "shunt" wire.

It ended up being a fun little car, I probably should have kept it!

 

[72RoadrunnerGTX]

I usually use a small brass machine screw and nut to lock the red and black wires together. Just wrap it securely with tape and/or heat shrink.

I use a cheap voltmeter from the auto parts store, tear it apart, and splice the movement into the factory cluster. The trick is to find one that sweeps the correct direction for your application.

This is the back of the cluster on a '68 Dart I did. I built my own solid state 5v voltage regulator (E-berg did an article on this in Mopar Action years ago but you can buy plug-and-play ones now) and took off power for the volt meter from there (small red and black wires running over to where the ammeter lugs were).

I glued the needle from the stock ammeter to the new movement with a drop of superglue:

I also put one of those solid state voltage regulators under the hood along with a properly protected "shunt" wire.

It ended up being a fun little car, I probably should have kept it!

I am curious, why? All stock? What issues were you having that lead you to decide to do this conversion? Did this resolve your issues? Was there an actual problem with the original ammeter or ammeter terminals/connections or more of someone said/wrote that that it should be done? Were the bulkhead Packard terminals by-passed as well?

 

[nitro_rat]

I am curious, why? All stock? What issues were you having that lead you to decide to do this conversion? Did this resolve your issues? Was there an actual problem with the original ammeter or ammeter terminals/connections or more of someone said/wrote that that it should be done? Were the bulkhead Packard terminals by-passed as well?

The ammeter was melted and the charging system wasn't working at all. Yes, the bulkhead was bypassed as well.

The work was mostly based on stuff written by Rick Ehrenberg in Mopar Action. There was a little article about how to build the 5v voltage regulator out of Radio Shack parts, info about bypassing the bulkhead connector, making the alternator shunt wire modification, etc. It was a fun project to do and the Dart never tried to BBQ itself again after that.

I picked that car up from a guy that tried to fix a throttle shaft vacuum leak with JB Weld. Gave next to nothing for it and it ended up being too nice to part out. I fixed it up and daily drove it for a while before selling it and moving on. The last I saw it it was at the dealer's auto auction in Tyler, TX maybe winter 2020. I might entertain buying it back if I could find it...

 

[72RoadrunnerGTX]

The ammeter was melted and the charging system wasn't working at all. Yes, the bulkhead was bypassed as well.

The work was mostly based on stuff written by Rick Ehrenberg in Mopar Action. There was a little article about how to build the 5v voltage regulator out of Radio Shack parts, info about bypassing the bulkhead connector, making the alternator shunt wire modification, etc. It was a fun project to do and the Dart never tried to BBQ itself again after that.

I picked that car up from a guy that tried to fix a throttle shaft vacuum leak with JB Weld. Gave next to nothing for it and it ended up being too nice to part out. I fixed it up and daily drove it for a while before selling it and moving on. The last I saw it it was at the dealer's auto auction in Tyler, TX maybe winter 2020. I might entertain buying it back if I could find it...

I see, I’ve gutted a few voltage limiters myself and installed Radio Shack 5v regulator ICs as well in the past. Spent a lot of time at Radio Shacks back then. Prefer the RT Engineering units these days.

I’ve read the Ehrenberg articles, more of a complete redesigned approach as I recall (Densos and all). Certainly don’t remember him promoting this kind of band aid “shunt wire” fix, leaving all the stock unfused wiring in place with all circuit protection defeated, as is being promoted widely more recently.

 

[nitro_rat]

I’ve read the Ehrenberg articles, more of a complete redesigned approach as I recall (Densos and all). Certainly don’t remember him promoting this kind of band aid “shunt wire” fix, leaving all the stock unfused wiring in place with all circuit protection defeated, as is being promoted widely more recently.

I agree. I can't find the articles now, they used to be on the Mopar Action site along with Disc-O-Tech and some others. A quick look around revealed that E-Berg now has a link to his eBay store at the Mopar Action address. I didn't see what I remember reading on AllPar either. I'm pretty sure I have hard copies of the articles around the shop somewhere, but I'm in SC right now and the shop is in TX so...

 

[nitro_rat]

I found them!

https://www.allpar.com/d3/history/mopar/electrical.html
Vintage Chrysler electrical repairs and updates (part 2)
Repairing vintage Chrysler - Plymouth - Dodge starters

MAD Electrical also has some good information on the subject.

Catalog

 

[72RoadrunnerGTX]

MAD Electrical also has some good information on the subject.

SOME “good information”, bulkhead by-pass maybe. The problem with the MAD article that everyone likes to promote as proof that all Chrysler ammeters will spontaneously combust for no reason whatsoever, most readers miss the part about the article stating it specifically addresses the late-seventies truck plastic framed ammeter/dash frame melting fiasco. Conflating this issue with every other passenger car, and earlier truck ammeter Chrysler ever used. Totally different issues altogether.

 

[65CopCar]

As soon the fuse link blows out by a heavy short on ANY section of the charging system, the engine will stall because the alt by itself is not able to hold a short, even less while short keeps sucking the power ign system requires. Regulator is on ign system network so at the same time will stop to feed the alt fields. So no need for fuse link on alt side…

The only source able to feed/keep alive a short where the fuse link enters in action is the batt. With or without engine running.

You are making too many assumptions. Including many of our cars have built in regulators.

As a degreed electrical engineer with 40 years of experience in the industrial electrical world with 29 years as a recognized subject matter expert this is my professional opinion and I'm sticking to it!

Not everyone will be as **** as I am on this.........