Part 5, The ’60-70s Chrysler Electrical System Demos, The Big PROBLEM with the “Shunt Wire” by-pass

[@stevenleslie9711]

Excellent explanation and demonstration of the power distribution of the Mopars. Your video makes things clear and obvious. I always knew that the ammeter bypass by itself was eliminating one of the lesser causes of issues. The appropriate distribution of power and reduction of current through the interior wiring is of great interest for myself. Installing relays to handle larger loads is a great way and commonplace in today’s vehicles. Thank you for sharing and you’re doing a great service to help others!!!

[@zerogmopars746]

This really shows how the stock wiring was designed for the stock alternator output of less than 40 Amps. Not perfect, but some very simple changes. Change 1: from the engine bulkhead connector, remove the alternator male terminal and connect to battery, using a fuse/fusible link if you don't want the alternator output wiring being the fusible link. This is pretty much like the last change you made. As noted, the Ammeter will show discharge and all the dash current it still going through a single bulkhead connector. The factory 12 AWG alternator output wire is still only sized for about a 36 Amp alternator. Change 2: You could move the fused battery terminal to the terminal that the alternator terminal was plugged into to by-pass the ammeter so it is non-functional, but still all power through one bulkhead connector, but no needle movement on the Ammeter. Change 3: bring the battery fused power through both the battery and alternator bulkhead connectors to split the load in parallel at the bulkhead connector. This would display a discharge at the ammeter, but only the battery side split of the current. Change 4: if using a higher output alternator, don't use the factory 12 AWG alternator wire at all, and use a larger wire gauge that can handle all the alternator output current. I mention these, because they are the "Lazy" and simple changes all done under the hood. These only help a bit. The wiring is protected by the fusible link, and the alternator output is it's own circuit. Still leaves the issues of the under dash wire sizing, and all the ignition switch wiring limitations. Change 5: not as simple, but remove high amp loads to relays. Head lamps, cooling fans, electric fuel pumps, A/C clutch, High output Amplifiers, power windows, and such. I like you showing loaded circuits too. I have a hard time trying to explain how the "ground" can change level under heavy loads like the cars starter. Keep up the good work, I appreciate the time you have put into doing these videos.

[@45BradB]

Firstly, I really appreciate the long form informative videos. They’ve cleared up a lot of questions I had. That said; what’s the answer? The faux-shunt wire bypass leaves the system vulnerable to a catastrophic short but leaving the system factory it can burn up under heavy load. I have a 440 auto 71 satellite with a/c and power windows. How do I wire the new replacement factory harness I have so I doesn’t go up in flames?

[@72roadrunnergtx]

These videos thus far have been focused on mainly misinformation about the stock system while running stock loads. I do plan the final part to cover not so stock loading while keeping a functional ammeter. Basically, showing how I have done my current ‘72s. ’72 RR/GTX 440+6, A/C, power windows, power door locks, 400 watt audio amp, and another 400 watts of Hella lighting. All the while retaining a fully functional and accurate ammeter. I did diagram this option in a video I posted last year about “load placement matters”. Take a look at that one, see if it makes any sense. Stay tunned for a tour of my electrical system upgrade suggestions in an upcoming vid. Thanks for watching.

[@noone7138]

Thanks! Count me as another that appreciates these a lot. A question for you. My challenger is pretty stripped except for a power top and AM 8-Track. If I'm running a stock wiring harness and accessories with the exception the ballast bypass for electronic ignition would my upgraded 70amp alternator be within the safety zone for my wiring harness?

[@72roadrunnergtx]

The upsized alternator, in of itself, doesn’t pose a threat or concern to the stock charging/electrical system until additional loads are added incorrectly at the battery. The loads determine what additional current will be flowing while the engine is running. The main advantage to running a higher than stock alternator with all-stock loads is more current available at idle speeds. That said, the pump for the convertible top will pull some current while in use. I would still by by-pass the bulkhead Packard terminals in the charge path or at minimum something like the described C-body recall by-pass in the video. Far safer then the “shunt wire”, direct alternator to battery by-pass, approach.

[@noone7138]

@@72roadrunnergtx Thanks for the insight. I like the idea of the C-Body by-pass. Factory solutions always score high with me. I'll probably go to that when I rip out my shunt wire and reconnect my Amp Meter. The funny thing is is I've only used the power top probably less than a dozen times since I bought the car over 30 years ago. Anyway, better safe than sorry.