I have replaced my amp meter with a volt meter in my 67 coupe. My son's 59 Pontiac dash caught on fire because of amp meter failure, it would have been catastrophic except his car is made out of metal. The volt meter works great and is more useful than the amp meter in my opinion . My question is the two wires (black and black/white) that hooked to the amp meter, should I connect them together or just leave them cut. Key on or off both wires are hot.

 

Take a look at your wiring diagram, I don't have one for a 67. I think the black w/white stripe is feed from the horn relay. I would unhook it there. Then the black wire is feed from the large post on the starter. Unhook it there! Both are 12v sources and should not be left energized if you are not using them, then they could short out under the dash and cause problems.

As a unsolicited opinion, I think both of these wires are protected by a fusible link on the 67 wiring harness. I wouldn't get overly concerned about them shorting out as the links do blow / melt. When you hook up your volt meter, how are you going to protect that circuit?? Are you trading an apple for an apple as far as potential fire hazard?

Hopefully one of the electrical experts will jump in and confirm my guess on the sources to the guage.

Ron

 

The C2 gauge is a "battery" gauge and not an "ammeter". The system current does not pass through it as it would on an ammeter, like the C1 and many other older cars had. Your fears may have been a little over thought, but you are correct that both black and b/w wires are 12 volts anytime the battery is connected. A very small amount of current is passing through these wires and it only take tenths of a volt to swing the "battery" gauge full scale
Having said that, I think the voltage gauge is practical in other ways as long as it matches the other gauges in appearance. Both the black and black/white wires should be removed as described by R66 described or you won't be any better off than you were with them connected. They will still have 12v on them laying around under the hood and under the dash. Just make sure you disconnect the correct black wire at the starter (ring terminal on large 12 volt connection) and the black/white that is connected to the red wire connection at the horn relay. Post up a picture of the gauge installed and let's see how it looks.

 

The C1 and other early GM cars had "full flow", unfused ammeters with 20-25 amps passing through them inches from the driver right at the dash; C2 cars (as noted above) use a very low difference in voltage potential to produce a reading....

Apples and oranges, you didn't need to swap your 67 gauge out for fear of a fire... If it was done to more accurately monitor the systems charging health that's legit...

 

I am guessing the 59 had no fusible links and probably very few fuses back in that era. Although the 67 Corvette was the first year for fusible links, I would still consider burning electrical insulation and copper the the fusible link "Fire" and could feasible touch or drip on a more combustible to start the "Fire", so the concern is not unfounded. Fusible links just provide a smaller "Fire".

However, the main concern I had with R66 is the old paper radio capacitors under the dash that deteriorated with age and the lead (wire) on one came loose and shorted to ground as I was working under the dash. That got me concerned. I would think everyone should consider going through the dash wiring harness and disconnecting all of these old paper capacitors.
As Smokey says "only you can prevent Vette fires. Forgive me.

Ron

 

I use one of these:

http://Zeltauto LED Digital Car Volt..._SQZbEbFZJK8EF

Steve

 

In those days GM divisions did as they pleased, some ran ammeters in series with all loads as did Mother Mopar but Pontiac for one used a shunt ammeter that used a low ohm resistor in parallel, many others did as well. I understand Chevrolet did not use a shunt in the C1. The C2 arrangement was likely intended to avoid the overcurrent hazards of a traditional ammeter in series with the load and I suspect the two wires were less expensive than a shunt type instrument which would have been preferable for accuracy.

However, a voltmeter is an improvement over both by conveying far more useful information than simply which direction current flows. An ammeter may show a battery that is not discharging, or not discharging very much, but it is a poor indication of how well an alternator or generator and its regulator are performing. Voltage regulators do that. When I built my 61 Plymouth I wanted period correct SW instruments but I wanted a voltmeter which SW only made with red and yellow sweeps that wouldn't look right in a 61 car. So they made me a custom version!

The voltmeter conveys useful information but as with the ammeter, the voltmeter must be properly wired in to see system voltage accurately. Voltage drop will affect the reading. The voltmeter should be wired to the horn relay bus lug on a C2, and I'll defer to Frank and the others as to best practice on a C1.

Dan

 

I replaced my amp gauge on my cars to prevent fires and they rely don't provide much information until it is too late.
A volt meter will tell you as soon as the alternator stops working, leaving you with a full 12V to get home.
A fuse at the gauge supply is necessary, although I have a battery shut off on all my cars and use it at all times when I park it. The red key is removable for security.



The batt. shut off is the red switch next to the speaker. in place of the cigarette lighter.
The amp gauge is there just to fill the hole in the dash.

 

Thanks to all. I will do the wiring as R66 suggests. To answer a couple of questions, the volt meter is just hooked to a fused "key on" source and grounded, easy. As far as the looks, the gauge comes from Full Throttle Corvettes and is an exact match to the cluster, about $80 delivered. For me personally I like a couple of things, "key on" we get battery info (12 volts) and with the engine running we get alternator info (14 volts). I was concerned about the fire hazard but you all educated me about that. Thanks again, this forum is a great source for me.

 

Here is info for Battery to Volt conversion ===> Click Here

Volt meter & white face gauges

 

Those 2 wires are the sensing leads for the old ammeter and yes they are probably hot all the time so you should disconnect them at the source. My online 67 wiring diagram from keystone corvette club shows the black wire transitions to orange near the starter and terminates at the starter solenoid which should be easy to identify. You what to lift just that wire from the starter solenoid and tape it back.
The black and white wire transitions to a orange wire which is a fuseable link that terminates on the horn relay. That should be even easier to identify/locate. Lift only that wire off the horn relay and tape that back also.
Myself, I wouldn't cut or remove those wires as they have a specific resistance that enables the ammeter to work correctly such that it can be returned sometime in the future. If you just tape them off at the old meter they will remain "hot" all the time and something I suggest you avoid though there are plenty of continuously hot wires in the car all the time anyways.

Hope this helps.

 

I much prefer amp over volts. Amps shows you the health of your entire electrical system, not just if the charging system is working. It is the reason all aircraft have amp meters. But what ever you prefer.

 

I agree with you that an ammeter conveys valuable information to a pilot. In an automobile, with a far simpler and less critical electrical system the charging system is really all there is to worry about, and, the voltmeter's information is more telling of alternator/generator operation than an ammeter. There's no reason not to have both though it is seldom done.

Dan

 

The issue is people need to know how a ammeter actually works to understand what is going on. With a volt meter all they have to know is green arc. But the amp meter will tell you everything you really need to know. Kind of the same reason the auto makers went to dumb gauges, people don't understand that all gauges fluctuate, for varying reasons.

 

I agree with you here as well. An ammeter gives a good indication of battery condition and load but has less to say about the source than that of a properly scaled and calibrated voltmeter. By way of your example an instrument on my Toyota Tundra indicates a range of 8 V to 18 V with not a whole lot in-between is an indicator and not a voltmeter, sufficient for acknowledgement that some sort of charging is going on but little else.

Dan

 

Volt meter will give you a great indication of output of your electrical system. It just needs to be interpreted. People need to know that it will read high at first, then drop, but should never read zero. It should also not go to high showing you that you have a high draw. It does everything a voltmeter does (except tell you exact voltage) but does much more. It should go up when things are turned on, then drop back down, etc. People would actually have to watch it for a while to know what is normal for their vehicle.

 

I would think that the voltmeter would be more accurate than the stock ammeter because the voltmeter is driven by ~12+ volts whereas the ammeter is driven by <2 volts. So, if there is corrosion in the wires or terminals, there is less potential difference to push current through the gauge with the ammeter.

As for condition of the system, I think it really wouldn't matter. If you turn on the lights, and the system is not charging, the voltage will drop below 12 volts and the gauge will reflect this. If the system is working properly, the gauge should show an initial drop or increase and taper off according.

 

A volt meter will not show you if a component is pulling to much power. But a amp meter will show you if it is putting out, if it is operating properly, and if it is not operating properly. There is a reason every aircraft in recent history has a amp meter, but lots don't have volt meters. Is it necessary on a car, no. But if I had a choice I would rather have a amp meter.

 

As a point of possible interest, all meter movements respond to current flow. The magnitude of current for full scale deflection varies with meter design. Some meters respond to currents in the micro-ampere range, others in the 10s of milliamps range.

Whether a meter reads Voltage or Amps depends on the external components around it and how they are connected.

A meter intended to indicate Volts will have a resistor of appropriate value in series with its windings to limit meter current to that needed for full-scale deflection at the maximum Voltage the metering device is intended to measure.

A meter intended to indicate Amperage will have a resistor in parallel with the meter windings to shunt some of the current around the meter, allowing only a percentage of the current to flow through the meter windings. In the case of our Sting Rays, that "resistor" is the large wire which connects the alternator to the horn relay.

So, any meter can be configured to read either Volts or Amperes. In either case there will be current flowing through the meter windings and it will be quite small.

Jim