This particular Hemmings article? The how? Maybe, the Why? Total BS. Just another propagation of the “spontaneously combusting” Chrysler ammeter myth. Strange the supporting pictures show a pristine ammeter and connections that supposedly left this Road Runner stranded. No sign of any previous high resistance heat damage at all.
As for some of the stated facts used to justify such a conversion, as pertaining to a completely stock healthy well maintained ’60-‘70s Chrysler passenger car charging system as originally designed and while the vehicle is in normal operation, no modifications.
“the fact that all system current has to flow through the ammeter for it to work”
Misleading at best, the ammeter does not require any current to “work”. Only battery charging/discharging current should be flowing through the ammeter while the vehicle is in operation, regardless of load demand. The only conditions the ammeter will register “full system current” is when the vehicle is not in use, should be no system current flowing at that time, or key on and engine not running. Once more, the stock ammeter can more than handle the stock system loads without alternator output.
“As the wiring ages, its electrical resistance increases”
Not factual, the electrical properties of a given conductor will not simply change over time. Corrosion, oxidation at terminals because of excessive over-exposure to moisture, over time causes resistance build up. Insulation break-down is due to excessive heat and/or ultra-violet light over exposure, general abuse, not simply due to age. There is plenty of well-preserved original 50+ year-old wiring in good condition safely in use today.
“As the output of the alternator increases, so does the amount of current going through the ammeter”
Absolutely not factual, again only battery charge/discharge current should flow through the ammeter while in operation. Healthy fully charged battery, that is almost 0 amps of current. All factory loads are on the alternator side of the ammeter at splice 1, or some cases, directly connected to the alternator ammeter stud. As the vehicle/system loads vary, the alternator output increases/decreases to cover the demand, all on the alternator side of the ammeter, this vehicle /system current does not flow through the ammeter at all on a healthy stock Chrysler charging system. All vehicle loads are to be on the alternator side of the ammeter originally as designed. Any loads on the battery side of the ammeter will source its power needs from the alternator through the ammeter and related connections because the alternator is the main power source when in operation, not the battery. This added current at the battery is registered as false charging current on ammeter and puts the ammeter and related connections well outside of its original design limits.
“Both create additional heat, often in the workings of the ammeter. It also doesn't help when carmakers use shunts to tune the ammeters, adding even more heat right at the gauge”
Again, not factual, shunts to tune ammeters? There are no shunts or shunt resistors, or any other heat generating components/devices, that will add “more heat”, within a Chrysler passenger car ammeter from this era, flat out wrong. Any heat damage at the ammeter is a result of excessive resistance at the ammeter studs likely cause by excessive current or abuse. There are no “workings” in the ammeter, simple solid brass buss, a permanent magnet. Needle responds to changes in the magnetic field as influenced by current flow though the buss.
Further on the article, it directly conflates the later plastic framed truck ammeters failures with the original earlier passenger car construction, makes no sense whatsoever. At lease the Mad Electrical article specifically describes their remedy as targeting the later truck plastic framed ammeter melting failures. It appears it is some readers of that article that conflate the two completely different ammeter designs.
These original passenger car ammeters from this time do not simply “give up the ghost” or “spontaneously combust” for no reason whatsoever. You want to modify your electrical system to what you believe will better handle modern accessories/loads, not comfortable with or simply don’t like the higher current potential in the dash or simply because that’s how it’s done today. I get it, go for it. If you are going to write an article to promote your modification, at least get your facts straight.
There is no way that the pictured ammeter left any vehicle stranded, leaving the article lead-in premise completely in doubt.
Kind of hard to believe that the
pictured rather rare mint condition Rallye cluster ammeter was sacrificed/cut up for a cheap voltmeter substitution based on the stated mis-facts.
, Chrysler applied the shunted ammeter system used on earliers 70s for C bodies onto B bodies by 75 and A bodies on 76 ( then of course M and F bodies )