Welcome to the Corvette Forums at the Corvette Action Center!

Simple midyear question.

If you put a voltmeter on the solenoid when the Battery meter reads + 40, you may find the battery is 12.6volts. If you also put the voltmeter on the horn relay at that time, it may read 14.5 volts. The Battery gauge reads the difference between the two places as +40 meaningless approximations of amps or something.

When the Battery meter reads negative, the solenoid probably reard something like 12volts and the horn relay may read 10.4volts - which the Battery gauge interprets as -40 meaningless units of gauge face.

If you want a reality check, put an ammeter on the battery or a voltmeter on the battery or dash circuit. I put a voltmeter on the instrument cluster.
 
Update. I picked up the replacement alternator late this evening and installed it right away.

1. I could only run the car for about 30 seconds.

2. In that brief time, the ammeter (or galvanometer, or whatever in hell it really is :D ) dropped from +45 at startup to +35. Hmmmm. Looks promising.

Why didn't I run it longer? The side-tubes are both off, and it is way too loud to run it longer, in the neighbourhood, until tomorrow afternoon. :eek

Why are the side-tubes off, you may ask? :D I'll tell that story soon. :naughty:
 
67HEAVEN said:
Why are the side-tubes off, you may ask? :D I'll tell that story soon. :naughty:
Click to expand...
How do you keep an admin in suspense????

















:W






-Mac
 
OK Mac,

You're an old electronic dude like me.
If I remember correctly, an analog ammeter is a voltmeter with a shunting resistor across the terminals so that it reads a "relative" current with regard to the voltage applied to the meter with respect to the fixed resistance of the shunt.
If the contact to the shunting resistor is loose or the resistor is increasing in resistance, the meter will read a higher than designed analog voltage.

Could this be the problem?

If 67 is seeing marked results with the new alternator, the point is probably moot, but I thought I would throw it out there for consideration.
 
wishuwerehere82 said:
...If I remember correctly, an analog ammeter is a voltmeter with a shunting resistor across the terminals so that it reads a "relative" current with regard to the voltage applied to the meter with respect to the fixed resistance of the shunt.
Click to expand...

The meter movement is simply a current sensitive galvanometer. It can be used in a number of different ways including an ammeter with a shunting resistor as you described. In the case of the AC Delco unit above, which is brand new, it can measure current in either a forward or reverse direction since the movement is zeroed at the center, 12 o'clock position. If a galvanometer is to be used as a voltmeter, a large resistor is placed in series with the meter movement and the resistor is selected for full scale deflection a specific range. :beer
 
wishuwerehere82 said:
If I remember correctly, an analog ammeter is a voltmeter with a shunting resistor across the terminals so that it reads a "relative" current with regard to the voltage applied to the meter with respect to the fixed resistance of the shunt.
Click to expand...
Yup, a shunt resistor of low resistance to avoid changing the circuit and the meter must be in series with the circuit.

wishuwerehere82 said:
If the contact to the shunting resistor is loose or the resistor is increasing in resistance, the meter will read a higher than designed analog voltage.
Click to expand...
Assuming the voltage remained constant, if the resistance were low, the ammeter would read low and vice versa.

wishuwerehere82 said:
If 67 is seeing marked results with the new alternator, the point is probably moot, but I thought I would throw it out there for consideration.
Click to expand...
My first thought was the ammeter itself was problematic, regardless whether it's new or not. The regulator was second. Hopefully, the problem is resolved. That's the most important part!!

-Mac
 
Ok Bob, the suspense is still killing me why are the side tubes off, or do we have to wait untill the afternoon.


Tom M
 
The shunt is a wire in the engine bay harness.

When it burns at the starter, the Battery meter fries unless a fuse has been installed in one of its lines.

PS If the fan power supply is moved to the alternator output terminal and the problem goes away, SNAFU (situation normal - for a Battery meter)
 
Try tape!
 
After several hours at the hospital, I didn't get around to running the car this evening. My dad is in his 80's and had a dizzy spell today that scared him. He thought he was having a stroke, so my mother called the ambulance.

After extensive testing, nothing (other than the usual problems for a person in their 80's) was found, so home we all went. :confused

Back to the ammeter (galvanometer) soon. :D
 
What do the numbers on the BATTERY gauge represent?

-40 what?
+40 what?

I always thought amps. Am I wrong?

If you haven't guessed, this question is a result of the Ammeter Issue thread. :D
 
I think its intended to be amps. Regardless of how its measured, its still an ammeter showing charging (or discharging) of the battery. Whether its measuring volts or not. If they intended it to be a volt meter, they would have called it a voltmeter. If it was intended to show you volts, the range on the gauge would probably have been +20 not +40. With a fully charged battery the gauge should probably be steady somewhere between the 0 and +20 mark when the engine is running. my .02 :)
 
Yup, the gauge face is marked in "amps", although the mechanism is simply reading a voltage difference between two points; it's taking the voltage difference (depending on which sense wire sees the highest voltage) and indicating the direction and strength of current flow based on a known fixed resistance (to or from the battery, as "charge" or "discharge"). My head hurts :D
 
You can imagine how many amps are flowing due to the relative voltage difference, since A-C cars came with 60+ amp alternators and the guage is still marked -/+40. The wire in the harness that is straddled by the gauge wires (and used for a gauge shunt) is not keeping track of everything the alternator does.

I put a 135 amp alternator in my 66 and the guage never noticed, so I switched to a voltmeter. IMO you need to at least add a 10gauge wire from the alternator to the horn relay if you use an alternator that can put out more than 40amps - especially if you hook the fans to the horn relay.

As I understand the electronics, the engine bay harness has a splice where all the red power wires in the engine harness come together. The regulator is actually measuring the need for power at the splice, not the battery or the horn relay. If you are using a "one wire" alternator without an external regulator, that is no longer the case. IMO either way, the harness cannot handle more than 50-60amps without help. I also put a 60amp fuse on the feed to the harness from the alternator for harness protection.

If your car does not have A-C, the simplest solution may be to add the power lead used to supply 30amps to the add-on A-C harness, but I would still add the helper line to the horn relay and add the fuse at the alternator - as I did on my A-C, electic fan, electric fuel pump, auxiliary headlamp, high power stereo 66.
 
To answer your question correctly those are "amperes". An ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes, therefore the name ammeter. Your ammeter uses an air core meter movement and is not a "galvanometer" and is the most modern design to date. It was designed to show the charging and discharging of your battery, and that is what it does, very accurately. Do not ask me to tell you what an ampere is or you will have a headache for sure. How many more questions can be asked and not correctly answered about this subject?
 
Ken Anderson said:
To answer your question correctly those are "amperes". An ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes, therefore the name ammeter. Your ammeter uses an air core meter movement and is not a "galvanometer" and is the most modern design to date. It was designed to show the charging and discharging of your battery, and that is what it does, very accurately. Do not ask me to tell you what an ampere is or you will have a headache for sure. How many more questions can be asked and not correctly answered about this subject?
Click to expand...

What is that in joules? :D
 
You must log in or register to reply here.

Corvette Forums

Not a member of the Corvette Action Center? Join now! It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Back
Top Bottom