Volt gauge wires

[Nacho-RT74]

Tell me about all the “more practical information” a voltmeter provides over an ammeter. Automotive voltmeters provide little more information than a simple idiot light, either charging or not charging.

Correct, and if you know your car, you can tell the voltage status just watching at the dimming lights everywhere as soon alternator is not working or is not enough. You don't need a gauge to tell it, but just for precision ( or down the daylight LOL )

IMHO ammeter instead, gets you a "predictable" big power failure ( no matter if just for couple of minutes ) with a hard and noticeable gauge needle reading change before being maybe somehow "late" just looking at a voltimeter. A load problem floats on before a voltage problem when you get a faulty alternator for example.

 

[bing69]

After reading a lot of the postings about the alt meter; I'm confused. When it comes to electricity, it doesn't take much. My alt meter is toast. Every time I connect the battery I get some spark. I disconnected both wires at the back of the alt meter and taped them up. Now there's no spark. I didn't tape them together. Car starts o.k.. From what I'm reading, If I bolt the two (2) wire together; it won't hurt anything and more things may work? I guess I'm old school, red was always positive and black was always negative, and never should they meet. But if the alt meter was just a in/out type splice, then I could see that.

 

[72RoadrunnerGTX]

The red and black Ammeter wires are NOT positive and negative. They are both positive and if while by-passing the ammeter you have not connected them together; the car should not start. If it does, there is some non-original wiring mods somewhere or the ammeter has already been by-passed elsewhere . How do you know the ammeter is ”toast”? Is it shorted? Is it electrically open?
On an old Mopar, never assume all black wires are a ground or is negative, sparks will fly.

 

[bing69]

72RoadrunnerGTX - Thanks for you fast reply. The alt meter is in a couple of pieces. I've only had the car since April and (thanks to you and other members) I'm learning more about the car every day. Great resource!

 

[andyf]

I am putting new connections on at the bulkhead inside and under the hood along with the blocks. I got the inside done and installed auto meter oil pressure, water temp, and volt gauge. My question is can i leave the factor AMP gauge unhooked at the bulkhead sense i got the autometer volt gauge or does that wire power something else under the dash? Trying to eliminate that fire hazard if I can.

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It is a complicated question that is difficult to answer. A lot of stuff is hung off the ammeter in a stock car since it is very central to the electrical system. I'd recommend that you start by looking at the wiring schematic for your car and going from there. You can cause yourself a lot of problems if you move wires around without knowing what you are doing. I usually shunt the ammeter since I don't want so much current flowing thru the firewall connector and then I add a voltmeter to the system. Not everyone likes this technique but it works pretty well. The original Mopar ammeters were not a great design so I usually recommended shunting them by adding a path directly from the alternator output to the battery when installing a modern alternator.

 

[72RoadrunnerGTX]

I usually shunt the ammeter since I don't want so much current flowing thru the firewall connector and then I add a voltmeter to the system. The original Mopar ammeters were not a great design so I usually recommended shunting them by adding a path directly from the alternator output to the battery when installing a modern alternator.

Can’t agree with that, the gauge itself is very stout by design. If the original ammeters have a design problem, it’s that the stud/nut/insulator connections aren’t more idiot proof for servicing 50+ years down the road. The primary design issue is running charging and vehicle current loads through Packard 56 connectors in the bulkhead connector and expecting them to last more than a year or two outdoors without corrosion, leading to resistance and resulting heat. On a healthy system, as designed the ammeter would never see more than the battery charge discharge current. Leave a good ammeter alone, by-pass the bulk-head connectors.

 

[bing69]

Well, I bolted the two wires off the alt meter and taped them up. No spark when hooking up the battery. I was hoping that some of the things that didn't work before would now start to work. Nope. Fuel, temp, dome light, and the horn still don't work. I bench tested the fuel and temp so I know they work. The horn did work and the black wire running to the horn relay is hot. I need to start looking harder at the firewall block. I've got a new, aftermarket, oil pressure, volt meter, and temp gauges combo that I plan on installing. Got a new, plastic coated, wiring diagram in the mail the other day. Should help a lot.