ammeter / voltmeter

[44070dart]

I have a factory ammeter in my '68 and aftermarket voltmeter also... the ammeter reads just on the minus side but voltmeter reads 14 volts.. why is this, the battery goes dead if I have key on and work on the four way or some other small drain for a half hour.. car running I removed the neg. cable with headlights and heater on and car runs the same.. why the different readings.. I don't know if battery is bad the way it goes dead so fast.. not on road yet.

 

[BIGSHCLUNK]

Sounds like a weak battery

 

[Nacho-RT74]

where is the ppl who supports voltimeters agains ammeters? LOL

@72RoadrunnerGTX one more to show ammeters eficiency LOL

A damaged batt could be a cause but also need to say you could check the bulkhead conections specially the black one coming from alternator. Voltage can run throught a hair but amperage needs good paths to feed everything. If some fail on some conection you can get burnt spots around due the heat caused by the missed conection resistance. Still getting voltage but not amperage. Amperes is what makes work everything based on a voltage rate, not voltage by itself. If the paths between alternator and ammeter or main splice into the dash harness are getting damage, the batt will never get a good charge rate, and batt will be sucked constantly while ammeter will read discharge.

 

[Xp29h]

Been posted before.. good idea

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

 

[44070dart]

I'll check the wiring ..then pull the battery and have it checked. Yeah those amp gauges worry me. The one in my Dart came loose and the car shut down completely and when I was looking under the dash moving wires I hit the amp wiring and it was loose, it sparked pretty good. I double nutted it to make sure.. More comfortable with voltmeter. Guess I'm going to line up with the anti-amp guys ...thanks

 

[Nacho-RT74]

did you really get the advertisement of your charging system status reality came from the ammeter and not from the Voltimeter ?

 

[beanhead]

I'll check the wiring ..then pull the battery and have it checked. Yeah those amp gauges worry me. The one in my Dart came loose and the car shut down completely and when I was looking under the dash moving wires I hit the amp wiring and it was loose, it sparked pretty good. I double nutted it to make sure.. More comfortable with voltmeter. Guess I'm going to line up with the anti-amp guys ...thanks

But....your amp meter is the one that is trying to tell you there's a problem! Your voltmeter's telling you 'we got 14 volts, all is right with the world'...except it isn't. The ammeter showing a discharge condition is your indication that something is not right...and yes absolutely make sure your connections are tight on the ammeter. As long as the nuts aren't loose on the studs you'll have no trouble with it.

 

[44070dart]

did you really get the advertisement of your charging system status reality came from the ammeter and not from the Voltimeter ?

what was that ?

 

[Nacho-RT74]

sorry, bad english. Is noty mother language and sometimes I get lost on my posts

I meant... if you noticed your ammeter is showing you the thruth about there is a failure on charging system ( whichever it is ) while the voltimeter is showing like everything was fine ? and you still are becoming on an antiammeter guy ? LOL

 

[44070dart]

OH yeah ..I will eliminate it .. two cars and two issues with it...50 year old wires, not worth the hassle to me.

 

[Nacho-RT74]

So when your brakes fail, or the coil or the gas pump, then eliminate those too... after 50 years not worth the hassle... LOL.

 

[Nacho-RT74]

Read this

http://www.dodgecharger.com/forum/index.php/topic,33574.0/all.html

 

[44070dart]

So when your brakes fail, or the coil or the gas pump, then eliminate those too... after 50 years not worth the hassle... LOL.

I don't think it's much of a comparison in any language .. I really don't need an ammeter. I have two cars and both of them have had ammeter problems. My dart had a loose connection at the ammeter and died on the road, it was sparking under the dash from a loose connection...

WHY guys insist on keeping something that is so potentially dangerous when their having trouble with it, in a fifty year old car, is beyond me. If I'm re-wiring the whole car, OK keep it. The worst that could happen without it is ......I have a dead battery. Oh no !!

 

[Nacho-RT74]

The electrical system ( ammeter included ) needs to be revised the same as the rest of the car. The problem is most of the ppl thinks wiring will last forever without consider the conditions has been working, more or less abused.

Gasoline is potentially dangerous too and you fix when detect a leak on gas lines. Is just about ppl underestimating the need for a good condition electrical system. But nobody really cares or take seriously about wiring and components. Then blame a forgotten and abandoned system like it was to live forever by itself.

Ppl takes more seriously how a camshaft works what does need to work properly matching with other components than how the ammeter works and keep it safe. Begins to modify or add new accesories without consider how the electrical system will act with the new adds. Then once again, blames the system.

I’m running a 80 amps alt with my stock “40 amps” ammeter and everything is safe, just because I studied the system to make it work. Serviced the ammeter just like serviced my carburetor or distributor, which by the way are dangerous if get some backfire!

 

[RJRENTON]

Gentlemen,
IMO....
It may be possible that the alternator has a bad diode, which would account for the low charge rate both in amperage and a lower voltage output. A shorted diode will cause the battery to discharge over time, even with the key off snd all electrical loads off. If any diode is OPEN, the alternator's output is reduced by half. If a diode is shorted, this will cause the battery to discharge thru the alternator's stator windings to ground, due to the resistance of the circuit.
The Mopar alternator is a three phase full wave bridge rectifier circuit and the loss of any diode or stator component will result in half of the total capacity or the unit.
BOB RENTON

 

[Nacho-RT74]

yes that's posible but he is getting good voltage

 

[RJRENTON]

yes that's posible but he is getting good voltage

Define "good voltage".... perhaps a full load test of the alternator is in order using a variable resistance carbon pile load device as defined by the FSM. After that, do a full load test of the battery and noting the battery's output VOLTAGE WHILE UNDER LOAD. Which should not drop less than 10.5 volts while under load. If it does, the battery is likely to be sulfated and should be replaced. Another test is to measure the battery's specific gravity with a hydrometer. The battery should read between 1.260 - 1.270 gravity if less, its an indication of a lower charge condition. As the battery discharges, the specific gravity will drop. All cells should be close to the same gravity...if one cell is significantly lower, that is the sulfated cell....replace the battery. Don't waste your time looking for bad grounds or loose connections....check the alternator's output and the battery's condition.

 

[Nacho-RT74]

well he told 14 volts per voltimeter reading

 

[RJRENTON]

well he told 14 volts per voltimeter reading

IF the alternator has an OPEN diode, under light loads, it will produce 14.5 volts; but, as soon as the alternator is subjected to a significant load, it cannot support the voltage level, indicating an open diode. Perform the FSM test procedures and even by pass the regulator by applying full voltage to the field, forcing it to charge at maximum, if it does charge, replace the regulator, if it does not, check the alternator's diodes, brushes and stator windings, if ok, replace the battery. Do you know how to check diodes in both directions? Same for the stator windings although they are connected in a "star configuration-with a common end connection". Also, check the resistance of the the rotor to make sure its working. The FSM is a grest source for values and procedures.
BOB RENTON

 

[Rusty 72]

My $0.02 but everyone should make it a priority to bypass that amp gauge.
My 72 had its entire electrical from headlight harness to dash harness fried because that wiring overheated.