Interesting Article on Ammeter vs Voltmeter

[72RoadRunnerGTX]

    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.

[dodj]

And the myth of the spontaneously combusting ammeter is perpetuated once again. By far the most factually inaccurate article I've read promoting voltmeter conversions to date.

I've seen six that had melted. Not a myth. Interestingly enough, one was in a Roadrunner similar to your forum name. The dash brown plastic bezel had to be tossed. Didn't lose the car or anything though.
Any high power connection needs regular maintenance. In cars, a non-shunt ammeter is as high power as it gets.
There is a reason all auto manufacturers stopped using them.

[jbaha]

My bulkhead was toasted also...! Smoke coming through dashboard. Getting rid of that bulkhead connector and ammeter was one of the best thing i've done to preserve my car.

[chargerdon]

I agree with roadrunner to a large extent but not totally!!!   I have seen several older mopars that have suffered signs of meltdown mostly at the Bulkhead Connector.   Look here is the real problem..   

First, Mopar only used 12 ga stranded wire from the alternator to the ammeter, and thru the bulkhead connector.   While it is TRUE that the alternator in most cases drives the entire electrical system and only puts out what is needed.   Then ammeters themselves are good for 60 amps, but 12 ga wire is only rated at 20 amp.   There are times when the alternator is putting out near full capability...this means between 37 to 47 amps on a 60's70's Mopar.   When, well to start with right after starting the engine...Often when mine is hot and sits for 10 mins before restarting, or on cold mornings when the car has sat for a week or more, it takes a bit of "cranking" draining the battery some.   Then after starting the alternator works hard to "recharge" the battery...  putting out way more than the wires rated 20amp.     THIS IS THE BIGGEST PROBLEM.   True, the high charging rate might only last for 1 or two minutes, but that can be enough to cause serious damage.

Second, the blade/spud connectors  at the bulkhead connector are also only rated for 20 amp.   When "recharging the battery" they are being asked to pass considerably more than that.    Ever have a dead battery, and get a "jump start" ?   This high charging rate of near or over 30 amp can last for 15-30 minugtes...   A HIGH DANGER POINT.

Third...  At night with engine running, but sitting at a traffic light with headlights on, and heater fan running, foot on brake for brake lights, possibley electric engine fan running, the amperage draw can far exceed 20 amps and the alternator at idle is not putting out...so the current draw from the battery can again exceed 25-30 amps...   

Lastly, the AMMETER itself is fine as it is just a BUS Bar inside...  its not the actual problem.

Running a 10 or better still 8 ga wire directly from the alternator to the starter relay alleviates 90% of this problem, especially if you ALSO replace the 12 ga wire from the starter relay with a 10 ga, and bypass the bulkhead connector and instead go thru the firewall with a grommet.   

[72RoadRunnerGTX]

     The myth is that these Chrysler passenger car ammeters from this era, in a completely stock configuration, by design, will just "spontaneously combust", "give up the ghost", or generally "be the cause of anything" at any time for no reason whatsoever. When in fact any heat damage present at the ammeter connections is caused by poor loose/high resistance connections or failed insulators, resulting from neglect, abuse, and/or misplaced added electrical loads on the battery side of the ammeter charge circuit that causes current over-stress though the complete charge circuit. Placing all connection points this circuit outside of its original design limit.
Yes, there are other connection points in this stock circuit much weaker than well-maintained ammeter studs/ring terminals and insulators. Bulkhead Packard terminals and some Molex disconnects in some later production that have failed at very high rates since these cars were new.
     The primary reason for any automotive production change, then and now, is total unit production cost. If you believe that the move away from passenger car ammeters (excluding the later Dodge truck plastic ammeter fiasco) back then was for any other reason, you would be mistaken.
     In the 60's-70's there were many Chrysler/Plymouth/Dodge products on the roads, every one of them with an ammeter in the dash. The vast majority of them went to their junkyard graves without ever experiencing ammeter issues of any kind. If this was such the issue as some make out to be today, would have seen it at the dealers back then. The examples still around today should have all burned to ground by now I would think. Saw plenty of bulkhead/ Molex issues at the dealers. Never saw any, then and or since then, unexplained ammeter/ammeter connection issues on a stock untouched or well maintained vehicle.

Strange the supporting pictures in this article show a pristine mint condition ammeter/ammeter connections that supposedly left this Road Runner stranded. No sign of any previous or current high resistance heat damage of any kind at those terminals. 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.

[dodj]

Lastly, the AMMETER itself is fine as it is just a BUS Bar inside... 

You're missing the point. It's not what you call 'the bus bar inside'. It is the connections within and without. High power connections are very susceptible to heat once a very small amount of resistance occurs. That heat continually expands and contracts the connection making it a higher resistance, which means more heat etc...snowball effect. Same thing happens with the B/H connector. As you say, more often than the ammeter. But the ammeter still suffers from the same condition.
If you meticulously maintain those ammeter connections, you will likely be fine. But people don't. So it will continue to be a weak link in your electrical system. I agree, the B/H is the weakest. But the full flow ammeter is a close second.

     When in fact any heat damage present at the ammeter connections is caused by poor loose/high resistance connections or failed insulators,

Exactly. It has proven to be prone to happen. If you are taking issue with what particular part of the ammeter causes the issue...well..fine. Call it what you will. Without the ammeter they are not there. So problem solved.

[72RoadRunnerGTX]

You left out the rest of that sentence.
"...resulting from neglect, abuse, and/or misplaced added electrical loads on the battery side of the ammeter charge circuit that causes current over-stress though the complete charge circuit."
"It has proven to be prone to happen."? Really? That these ammeters are prone to burn up for no reason whatsoever, with little to no current flow at all through the ammeter under normal heathy stock operating conditions, without any external influence? Where is the proof of this?   

[dodj]

I said if you take care and maintain your ammeter connections you will likely be fine.
You say the overheating is caused by neglect, abuse etc.. which to me is a failure to maintain.

We're saying pretty much the same thing here.

The only difference is our conclusions as to how to deal with it.

[Filthy Filbert]

"well-maintained"

that's laughable.   

Yea, because so many people would regularly disconnect their bulkhead connectors and clean and maintain them.   Everyone knew that at every oil change you were supposed to climb in upside down and put your head under the dash to check, clean, and tighten the connectors at the ammeter. 

And nobody ever left their lights on, draining the battery, resulting in the alternator pushing 40 amps through a wire rated for 20...

[mopar jack]

A good article by mopar action from 1999. https://www.allpar.com/d3/history/mopar/electrical.html

[mopar jack]

Issues related to ampmeters were still around in the 1980s, The aviation industry had a TSB to correct ampmeter problems. http://www.spookmate.com/N4870T/SB-811a.pdf

[72RoadRunnerGTX]

    Not suggesting a safe healthy reliable electrical system/ammeter requires "scheduled" maintenance per se. When I refer to "well-maintained" in these electrical discussions, simply meaning maintaining the electrical system in a known good operating condition as time passes. Or as the English say, "in good nick". There is nothing about these cars that was designed to last anywhere near 50+ years, some electrical upkeep is to be expected. Know and understand the state of your electrical system always, modified or stock.

   When modifying, understand what impact the modification has to the remainder of the stock electrical system as originally designed.

   To be clear, I don't leave any of my cars completely stock. The original circuit design is intact, including the ammeter. Charge system wire sizing is changed accommodate the increased current potential of the 100+amp alternators. All unnecessary assembly line disconnects are by-passed, first and foremost the bulkhead Packard terminals. As well as all stock loads, several current demanding accessories are normally added (on the alternator side of the ammeter). Can run them all at the same time with the engine running, centered ammeter, no fear.

As for Piper Service Bulletin, for this example, yes, a shunted ammeter design allows for relocation of the higher current connection points but does not eliminate them altogether. Loose or poor connections at the shunt can still a very big problem for an aircraft, can lead to a much worse outcome than being stranded on the side of the road. Good thing regular aircraft maintenance is strictly enforced, and these types of connections are subject to rigorous periodic inspections. Too bad the complete elimination of ammeters, voltmeters only, from aircraft is not feasible. Again, any serious monitoring of DC circuits involves ammeters in some form.