Every wonder why late model cars don't run an amp gauge

[Mike V. Florida]

Jim Parker originally posted this question in another thread. I thought it was a good questiona nd I thought it best to start another thread.

These are my thoughts and I have no basis of fact to back them up.

Lazyness, well maybe that is the wrong word. As the automobile became a everyday item of use by the American public, and the roads became better and even designed for pleasure drives (Parkways), repair shops also became more common. The skills/tools of the mechanics increased so the indicators changed as well. From guages with needles to "idiot" lights.

The ampmeter is actually a very valuable tool already installed in our A's. If your car won't start you can see the points open and close by looking at the meter. Are your brake lights working? Put your foot on the brake and see the discharge increase. Same for head lights. Does your horn not work, push the button and watch the amp meter, if it moves and the horn not sound the wiring to the horn is most likley good or at least you don't have an open. (The 30-30 meters don't move as much as the 20-20 meters)

A volt meter, you have correct voltage is about the only thing it can tell you.

[Jynx]

if an amp meter shorts there is chances of fire and burning the wiring harness

[Doug in NJ]

One limitation of ammeters is that it is hard to read small changes, since they have a +-30 amp full scale. Sort of like trying to check your idle speed on one of those aftermarket tachs with a 90-degree needle swing and a 10,000 RPM top scale...

Don't some light aircraft have an alternator output meter instead of an ammeter?

With all the computer stuff in a modern car, it could measure charging current and battery voltage, and give you mere detailed diagnostics that you could get from an ammeter.

BTW, do modern cars have an OBD II parameter for charging current or alternator output?

Doug

[Frank Miller]

You would need a huge wire to the dash that all the current runs through or some kind of current coil to transmit the current value back to the dash. A volt meter will tell you whether you are charging or not. Also with voltage regulators there is no need to monitor the amps as you do in a model a.

[bogiediver]

Frank-

Would that hold true with the EVR in place of the cut-out? Considering doing the EVR. Tom W never got back to me on my PM to him and I understand he is the expert...

Any help appreciated...

[Patrick L.]

Sponsored Links (Register now to hide all advertisements)

Its a matter of wiring placement and if an ammeter fails[opens] you're walking if you don't have jumper lead in your pocket.. Volt meters are fine for newer vehicles, but, I like ammeters on the older cars especially when diagnosing something..

[MALAK]

Actually I think the answer is a combination of the previously mentioned answers.

As with any production car cost is a factor. Most people now days want to just get in and go and rely on the computer/electronics to determine if the car is functioning properly and therefore wouldn't use (or know how to use) an ammeter. Therefore we have idiot lights.

The advent of EVR/computer controls further negated the need for an ammeter, modern charging systems/batteries are very reliable.

Also, Frank is right, a modern car with lights, A/C, F.I., ignition, electronics, and accessories could easily pull 50A continuous and peak much higher. To use an ammeter would require a shunt or large wires from the alternator through the firewall, to the meter, to some distribution point. With increased current comes increased risk of electrical fire due to poor connections.

Lastly, starting at about 50A most ammeters require a current shunt which is a calibrated resistance that produces a voltage proportional to the current flowing through it. The ammeter then is actually a voltmeter calibrated in amps. This then is additional parts and complexity (and cost).

[Bruce Adams]

Could you imagine a modern car having EVERY circuit routing through an amp meter?

I went from 8 ga to 12 ga feed wire when I converted my boat from amp meter to volt meter, and it has very few power demands.

[BILL WILLIAMSON]

On ANY car, the MAIN feed wire from the battery, passed through the loop of an induction type ammeter, would work perfectly! Induction type ammeters don't get hot or burn out.
Ammeter's job is: negative= how many amps is coming OUT of the battery, positive= how many amps is going INTO the battery!
If you don't agree, just ask those "little men" that run around inside the wires making electrical things happen.

[Gord. B by the bay]

todays drivers do not look at an ammeter when driving but the red light on the dash gets their attention real quick
Gord. B by the bay

[tmiller6]

One clarification. In a modern car with an ammeter, only a portion of the current is going through the ammeter itself. There is not a huge cable going to the instrument panel. Instead a shunt is installed in the wiring harness and a small portion of the actual current flow is measured and multiplied accordingly. So, if the ammeter fails, there is no massive failure in the rest of the harness or the charging system.

[boboran]

I repaired and replaced ammeters in cars as old as 1935.Plymouth,dodge, and chrysler had two problems with their ammeters. They were copper and brass studs pressed together. As the vehicle aged the copper wiring developed resistance and as you know resistance causes heat, kinda like a common toaster.In the sixties and seventies they also had a weak bulkhead connection that melted and fell apart. the ammeter in these chrysler vehicles were mounted in plastic also, which burned quite regularly. Back then I fixed the ammeters by soldering the ammeter threaded studs to the copper housings,and bypassed the firewall. Ammeters also add extra length to the main battery source which can also cause resistance. Todays cars have too many amps to use:high amp alts,power windows,power seats ,computers etc,etc,etc chrysler finally quit using ammeters in the early eighties. Took their tech`s fifty years to fix.

[PC/SR]

I suspect the OEM's changed to voltmeters because they are cheaper and easier to install, especially in high amp draw conditions as noted. They also provide information not only if the generator is charging, but can give a general idea of battery condition. Check the volts when the ignition is turned on, and compare it to volts while cranking. A good battery will not drop the voltage much, if at all, while a weak battery will show a significant (2 volts) drop. Each have their advantages and limitations.

[steve s]

Originally Posted by BILL WILLIAMSON

On ANY car, the MAIN feed wire from the battery, passed through the loop of an induction type ammeter, would work perfectly! Induction type ammeters don't get hot or burn out.
Ammeter's job is: negative= how many amps is coming OUT of the battery, positive= how many amps is going INTO the battery!
If you don't agree, just ask those "little men" that run around inside the wires making electrical things happen.

I would have said it a bit differently, but no better.

As I see it, the loss of the ammeter is only one symptom of the problem: temperature and oil pressure gauges have gotten rarer too. I would blame the change on cost cutting--idiot lights must be cheaper than gauges--EXCEPT for one thing: My new Subaru has ADDED a new and totally useless gauge having something to do with instantaneous fuel economy BUT IN A TOTALLY OPAQUE, UNCALIBRATED WAY. So, I am left to assume the explanation is a general dumbing down.

Steve

[MikeK]

Originally Posted by steve s

. . . My new Subaru has ADDED a new and totally useless gauge having something to do with instantaneous fuel economy BUT IN A TOTALLY OPAQUE, UNCALIBRATED WAY. So, I am left to assume the explanation is a general dumbing down. Steve

Driven by sales? I was doing a little tire kickin' at the Chicago auto show. A young couple was looking at the same convertible I was. The lady sat in the seat and the rep waved the radio signal thingie (no more key). About 999 little cryptic shaped indicator symbols lit up. Her response: "Oh, Richie, look at all these neat little lights! I just walked away. Definitely not the indicator lights that came to mind when I thought "idiot".

[Cool Hand Lurker]

".......cryptic shaped indicator symbols...."

Maaaaannnnn..... I hate them things! Who knows what they mean?
What was wrong with words in english?

[Milton]

Originally Posted by Mike V. Florida

A volt meter, you have correct voltage is about the only thing it can tell you.

Au contraire, it can also tell me the battery condition prior to it failing. It can tell me when things are energized with the car not running. It will show battery voltage under a load i.e. battery test.

Originally Posted by Patrick L.

Its a matter of wiring placement and if an ammeter fails[opens] you're walking if you don't have jumper lead in your pocket..

Jumper lead i.e. bobby pin, paper clip, beer can, any wire wrapped around the terminal box nuts etc. It has to be a major problem before an A gets walked away from.

[Tom Wesenberg]

BTW, you don't have to run full charging current throught the ammeter. Chevy pickups in the 70's had 2 small fuses in the wiring harness that ran along the firewall. Either end of that aprox. 3' wire between the fuses had small wires running to the ammeter. When the ammeter didn't work just look for one of the fuses to be blown, however everything else on the truck still worked as normal.

[RichPA]

I think Bill W hit on it, an inductive meter would be non-intrusive. True, todays "idiot" lights are more idiotic but I think its the only way to get today's drivers attention. Almost all vehicles produced today have the charging system both monitored and controlled by the PCM(computer). This way emissions and fuel mileage can be the best possible as the alternator is a large load in the engine.By tweaking every system on the car it all adds up to better mileage. Diagnostics when theres a problem? thats another story.

[trulyvintage]

If you kept the ammeter, where would you put the digital stereo controls ....






Jim