The dreaded “ticking time bomb” factory Ammeter

[72RoadrunnerGTX]

Continued from another thread that had gone off topic and for some reason won't die out. Apologies to the OP (velrob) of that thread for the hijack.

Went to Advance Auto today. Couldn't find an ammeter in the "performance section." Asked the dude behind the counter. He looked at me like I was crazy, then said "Why would you want that? Do you want to burn your car up?"

Exactly.

Are you serious? That’s your back-up for all the BS you’ve posted? The guy behind the counter at the local parts store? We all know about the vast wealth of classic car knowledge and experience that can be had from the kid behind the counter at the corner parts store these days. Know, ask him to explain the inner workings of a carburetor. Try this, ask him for a matched set of v-belts for factory AC compressor/alternator/crank. I was never able to find anyone at those stores lately that knew what a matched set was. At least this explains where some of your mis-information is coming from.

Maybe it’s time you start yet another thread over in the electrical section about your take on the “ticking time bomb ammeter” bs. This thread’s been hijacked enough, is now way off topic.

LOL! I was pointing out they had all kind of volt meters, but no ammeter.

Hey, so I figure I'm using 160 amps when I turn the car on before the engine is started. Do you think that is enough to blow the ammeter if I were to listen to your antiquated advice? I think I might burn my old ammeter just to see. I expect it to get REALLY hot before it smokes. Should be fun.

If in fact your car is drawing anywhere near 160 amps pre-start, then your electrical system loads have been highly modified and would not be considered “as originally designed” as I have prefaced all of my factory ammeter comments. What pre-start loads would account for 160 amps curiously?

With good stud head to copper bus contact, tight clean stud connections, no stud to cluster frame contact, I’d expect you may detect some warming around 100 amps or so. Now, loosen up the connections, get some corrosion between the stud heads and the copper bus, crush the insulators to the point that they no longer center the studs in the cluster mountings and loosens up the connections even further, then dial up some current to see some fireworks.

 

[Triple Black 73]

Yeah and all you can say in defense of the ammeter is "MaMa mOpaR bUiLt iT lIkE tHaT aNd It gOoD eNoUgH fOr mE!" and "iF yUo KeEp ShO bAtTereeeee! cHarGeD u wOn'T hAvE nO iSsUshOeS!!"

Yeah, 160 amps. That's what I figured as the design max. Do you think it would blow the $%@# out of an ammeter? It's a whole lot more than the stock 35 amp factory design.

Do I actually pull that much? No. But could it? Oh, yeah! So, as an engineer, I design for the max plus a buffer. Do you now see why I ran a 4 awg from the 220 amp alternator to the 1000 cca battery, then 4ga from the battery to a 200 amp circuit beaker, then 8ga to the car and three 8ga to a 180 amp fuse box? Ain't no ammeter gonna work in that mess, sonny!

 

[Triple Black 73]

With good stud head to copper bus contact, tight clean stud connections, no stud to cluster frame contact, I’d expect you may detect some warming around 100 amps or so. Now, loosen up the connections, get some corrosion between the stud heads and the copper bus, crush the insulators to the point that they no longer center the studs in the cluster mountings and loosens up the connections even further, then dial up some current to see some fireworks.

Dude, I was getting "warming" just last year with a new 1000 cca Optima battery and a 25 year old 65 amp alternator. The issue was the battery would drop to 12.4 volts from just sitting and the old alternator had to crank out everything it could mustard across the ammeter just to equal it out at 13.8 volts.

 

[72RoadrunnerGTX]

What's the OHMs across an ammeter?

Just happen to have a decent unmodified 47-year-old one on the bench. Strange it hasn’t spontaneously combusted up by now, right? Measured resistance, copper bus about 1.5” long, with a cross sectional area of about .008” at its narrowest, equating to roughly a 9-10-gauge copper wire.

With tight mounting studs, correct stud head to bus contact tension;

With lose mounting studs;

What’s your point as it relates to the original use of the ammeter?

 

[Triple Black 73]

Thanks! It's too hot outside to pull my ammeter for testing.

So, 35 amps at 0.1 ohms produces 120 watts of heat. And I'm assuming this was room temp (73 degrees)? And 35 amps at 2.2 ohm produces 2600 watts of heat.

Looks like the issue with ammeter burning up is indeed with the connection of the studs to the bus plates. So, technically you're right in that the little meter in the middle doesn't burn up, because the stud connection will go up in smoke long before the meter does.

Thus, the only defense you have makes prefect sense. That being, make sure the ammeter doesn't move, and it does move, fix it right away! (else it's going to start heating up)

Thus, it is a ticking time bomb if too much current flows through it or the stud connections ever come loose.

 

[Triple Black 73]

And 160 amps at 0.1 ohms is 2500 watts!

 

[72RoadrunnerGTX]

Thanks! It's too hot outside to pull my ammeter for testing.

So, 35 amps at 0.1 ohms produces 120 watts of heat. And I'm assuming this was room temp (73 degrees)? And 35 amps at 2.2 ohm produces 2600 watts of heat.

Looks like the issue with ammeter burning up is indeed with the connection of the studs to the bus plates. So, technically you're right in that the little meter in the middle doesn't burn up, because the stud connection will go up in smoke long before the meter does.

Thus, the only defense you have makes prefect sense. That being, make sure the ammeter doesn't move, and it does move, fix it right away! (else it's going to start heating up)

Thus, it is a ticking time bomb if too much current flows through it or the stud connections ever come loose.

For the next experiment, let’s see what can be done about the stud heads to bus resistance when the mounting nuts lose some tension. Simple mod, took all of 5 minutes to add a little solder. Been doing it for years.

 

[Triple Black 73]

Nice. Now smoke it. Put 50 amps through it.

 

[72RoadrunnerGTX]

Not this one, in too pristine a condition and for a Rallye cluster. I have a couple standard clusters in storage I may do some destructive tests on sometime. Curious too just what current it would take to open the bus up at its narrowest part. With the copper bus at about .008” cross sectional area at that point, likely will to take 100+ amps to open it up. Your theoretical 160 amps may do it.

 

[72RoadrunnerGTX]

For the sake of discussion, here is an E-body standard cluster that came with the current project. No plans to reuse it. No outward sign of ammeter problems except it appears not level in its mount but closer inspection shows it suffered from heat damage at one of stud heads, enough heat to burn away the insulator, reducing the stud head tension even further, chain reaction, more resistance/heat, no inside insulator, then the beginnings of arcing to the cluster frame. The other stud shows no sign of heat.

 

[Nacho-RT74]

There is a threath I found quite ago about replacing and solding the studs...

https://www.dodgetalk.com/forums/showthread.php?t=252130

I fixed a 70 Charger ammeter maybe 10 years ago with lead over the studs just like you shown 72Roadrunner GTX

 

[Triple Black 73]

Ok, I'm going to yank mine.

There is a threath I found quite ago about replacing and solding the studs...

https://www.dodgetalk.com/forums/showthread.php?t=252130

I fixed a 70 Charger ammeter maybe 10 years ago with lead over the studs just like you shown 72Roadrunner GTX

Nacho, High Priest of the Church of Ammeter, welcome. We were expecting you.

 

[Nacho-RT74]

LOL...

I'm getting tired on this. I can't say the ammeter system is perfect, but is not unperfect either. Depending on your car needs. On a pretty much stock car with a bit of accesories added,. the STOCK ammeter is quite enough and can be get them work PERFECT if the correct considerations are on the table. Most of the ppl on this car hobby wants an MSD system to get the car out just to buy the newspaper or get a coffe, where the stock system is enough for this! So this applies the same for the ammeter too.

Would be great to have 80 amps rate ammeters ? sure, but if you get your car correctly balanced with a good alt, you won't ever notice the 40 amps ammeter is there on the system being overloaded and just will require some touchs here and there ( bulkhead and wiring ) to be happy with the way the stock system works.

Where the problems begins on this ? when you don't understand how the amm works or have no idea what the reading means. Most of the ppl could think a deadly centered amm will mean your alternator is not working because factory misslabeled the gauge as an ALTERNATOR gauge, which IS NOT TRUE.

next big mistake, take to mechs to add accesories straight to the batt post ( incorrect on ammeter equipped cars ) or upgrading to bigger capacity batteries keeping the stock alt... huge mistake!

and I can keep explaining on this forever. But most of the ppl is not toward to learnt about this and run the easy way... straight wires to starter relay post! If ppl think on this just like analize what camshaft to choose to your car, less AMMETER FAILURES threads will float on... Most of you are so lazy to analize and understand the charging system and are fears dominated LOL.

most of ppl don't think the electyrical system is an intergral part of your car like suspension, brakes, engines and transmissions. And electrical section is way cheaper, faster and cleaner to fix and upgrade than an engine or whatever other part of the car... if you care about it!

 

[72RoadrunnerGTX]

Would be great to have 80 amps rate ammeters ?

Ask and you shall receive

 

[Nacho-RT74]

Yes I talked about that because i have just right that one saved on my favourites, but never have seen one for Rallye cluster. These were made for fleet cars I guess ( cops and cabs ) and as far I know none of them got Rallye cluster?

 

[super-bee_ski]

Good thread!

 

[Triple Black 73]

LOL...

I'm getting tired on this. I can't say the ammeter system is perfect, but is not unperfect either.

Yet, you go to a lot of effort to convince others to keep an ammeter, for what end?

To see the battery charge/discharge? Who the hell even care?! Volts are more important. When I realize my alternator wasn't big enough, I didn't see it via the ammeter, I saw it with the volts dropped to 12.7. Heck, 72Roadrunner and noSnow admits to using battery tenders to save their ammeter from being 'stressed'. My battery goes to 80% from just sitting after a few days, and it still puts out 800 amps at that state. The battery could suck up most of the power the little 65 amp alternator could put out and all of that charging power went over the ammeter and produced heat, to the tune of 100+ watts of heat.

So, why does it even matter? If you bypass the ammeter, you avoid all possible issues related to it. Not just some, but all. There's a reason why every single modern car for the last 30 years wires the alternator directly to the battery. There was a reason why these cars had ammeter and that reason no longer exists. The batteries where terrible back then. They would catch fire when over charged. The generators could fail, and catch fire. The ammeter could fail, and catch fire. Heck, the ammeter could catch fire just sitting with the headlights left opened!

The fleet design was OK, soldering the threads is very good plan, 8 awg to it is fine, but avoiding it completely is by far the best solution. And you're not using a ammeter one with 160 amps possible draw.

 

[72RoadrunnerGTX]

72Roadrunner and noSnow admits to using battery tenders to save their ammeter from being 'stressed'.

If you’re going to paraphrase me, get it right. I mentioned in one post that “a battery maintainer is recommended”. I use a recently purchased Digital 1200 with the current Optima batteries in an effort to extend the life of the batteries only, as my cars sit unused for weeks at a time unfortunately. Any charging current relief is a benefit but not a must and not factored into the circuit design as it is currently. I ran the first Optima eight years without using a maintainer, never saw anything close to what you predict as charging rates for a partially discharged battery under any real-world conditions experienced. You seem to believe the charging rate is directly proportional to the current charge level, the battery capacity and determined by a voltage differential.

Now, as for advocating the use of the ammeter, I have not posted, or read any posts, in this or the original thread pushing for the use of ammeters in any vehicle, let alone your highly modified high load (THEROITCIAL 160 amp) system. I have read quite a few posts pushing for by-passing of the “ticking time bomb” ammeter on everything. Most of the inaccurate, mis-leading, and irrelevant specific reasoning you posted to support that position; I’ve simply countered with facts for those who do care about retaining originality on their classic Mopars.

I’ve designed and built a variety of 12-volt high load mobile systems for a variety of vehicles, including boats. A few non-Mopars running a similar battery ammeter system as well, older exotics primarily. Frankly, in most cases it is better to run a second deep-cycle battery for the high loads and related circuits and separate out this circuit completely from the vehicle’s original electrical system. Then the use of a correctly installed battery isolator to charge the aux system’s battery.

BTW, it’s really simple, on a healthy correctly wired original system, if the ammeter shows a discharge while the alternator is operating, your total loads are out pacing the alternator's output capacity. Don’t need a voltmeter for that.
I have close to 250k miles on a late model GM produced daily driver with a volt meter. A couple of alternators, a few batteries, over the years. Volt meter only ever showed 14 volts or 12.6 volts while running. I could see the alternator had stopped functioning, that’s it, may as well have been an idiot light. No information as to what the current discharge rate was, no way to gauge just when the vehicle will leave me on the side of the road. The battery failures were mostly without any advanced warning with the volt meter, normal 14 volt reading up to a no start condition. At least with an ammeter, there would be good chance it would have registered abnormal charging rates for some time prior to complete battery failure, giving the user a chance to have the battery load tested/replaced before being left stranded somewhere.

Ammeters are only useless to those who don’t understand completely the information they provide as it relates to the original charging system function. Admittedly, this would include likely 99% of the owners of these cars then and now.

 

[Nacho-RT74]

Yet, you go to a lot of effort to convince others to keep an ammeter, for what end?

To see the battery charge/discharge? Who the hell even care?! Volts are more important.

Amperes ( based on a volt rate ) is what makes the car ( or anything, not just car ) to work, not volts by itself. You can get 120 volts to feed your garage bulb the same than 120 volts to feed your welding machine... but both use diff amperage to work. If you don't have the amperes source and the paths ( conector and wires allong with the breaker ) able to feed the welding machine, simply won't work or maybe will burn something around, but the bulb will light up without problems... and both still are 120 volts

 

[zsn0w]

Heck, 72Roadrunner and noSnow admits to using battery tenders to save their ammeter from being 'stressed'.

I'm going to assume this is talking about me? I've never used a battery tender. Don't make things up about me.