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Discussion Starter #1
Okay experts.... Assuming I reversed the + and - connections on a voltmeter.... would the guage read backwards. Mine is showing constant discharge but the battery hasn't died.... (yet!)

I don't have a tester for the altenator or the aquired knowledge to use one yet either! hehehehe


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I want to die in my sleep like my grandfather...

68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28, less than 14,000 miles on it!

Not screaming and yelling like the passengers in his car.
 

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Yes, if you have an analog voltmeter, the needle will try to go below zero if you reverse polarity.

When you say it's showing constant discharge, what exactly is it showing?

Is the reading continually dropping? Or is it reading a steady voltage below what you think it should?

It's possible that you have a loose connection where you're reading your voltage. There could be a load pulling off the circuit where the voltmeter is connected.

Does the voltmeter read the same whether the engine is running or not? It should give a higher reading while the engine is running if the alternator is charging.

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Chad Landry
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'68 El Camino, 357, L31 Vortec heads, 700R4,
8.2 10-bolt, 3.55 gears, Auburn Pro Posi.
 

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Discussion Starter #3
Chad, I have a amp guage that has been converted to a voltmeter.

I did some testing today. When I start the car it shows discharge and the one wire alternator does not show any output. Once I accelerate the motor the alternator starts to put out 14+ volts. The gauge still shows discharge slightly.

When the car is off the gauge drops down to full - (D) and if I put the headligts on it comes up just a bit from the very bottom of the guage but no where near + territory.

After letting the car run enough to get the battery charged the gauge did move slightly to the + (C) side of the guage.

So, could this all be "normal" if the battery has been sitting and is partially discharged?

I suspect I may just not know exactly what I shoud be "reading" from a voltmeter.

I do appreciate your help!

Mike

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I want to die in my sleep like my grandfather...

68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28, less than 14,000 miles on it!

Not screaming and yelling like the passengers in his car.
 

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Sounds good to me. My one wire alternator does the same thing. It doesn't excite until I hit around 1100 rpm.

I got a "little black box" that connects to the alternator which apparently mimics the idiot light circuit. They use 'em on low rpm diesel engines with GM alternators. I have yet to try it out.

I don't understand how the ammeter was converted to a voltmeter, but it sounds pretty cool.

Since you're measuring 14+ volts at the alternator, I assume you have a voltmeter to check under the hood with. Check voltage at the battery with the car off. Then check it with the alternator putting out. That will tell you whether you have a problem or if everything is normal. You may just have too much resistance in the wiring that feeds the ammeter/voltmeter in the car. A loose connection, corrosion, or just old wiring.


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My Web Page (updated 06-21-02)

"Long Live Freedom!"

Chad Landry
TC Member #643
ACES Member #4556
'68 El Camino, 357, L31 Vortec heads, 700R4,
8.2 10-bolt, 3.55 gears, Auburn Pro Posi.
 

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Discussion Starter #5
All new "Painless" harness in the car but the + to the voltmeter also supplies power to all other gauges or the gauge could be a bit "off" from the coversion.

The power at the battery was just under 12V when I started testing and jumped to 14+ once the alternator activated so I know I have everything in order but possibly the voltmeter which I would believe should also be getting 14+ volts and showing + (C) when it shows slight -(D).

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I want to die in my sleep like my grandfather...

68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28, less than 14,000 miles on it!

Not screaming and yelling like the passengers in his car.

[This message has been edited by Redrum (edited 09-15-2002).]
 

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When I did the conversion on the gauge I set the pointer (needle) at mid scale with a calibrated voltage source set at 13 volts with an overall range of 8 to 18 volts. So mid scale should be 13V. I’m guessing that the gauges are fed from one of the fuses in the 18 circuit painless fuse block. Measure the voltage at that fuse. It should agree with the dash gauge. Is this fuse/circuit dedicated to the gauges? Anything else connected to this circuit can reduce the voltage at the gauge.

I don’t know how the painless wiring harness gets power feed from the battery to the ignition switch and to the fuse block but a high resistance connection in any of the connections can result in a low voltage at the fuse block. Another thing to consider is that depending on what you have on or the load you have on the switched (ignition switch) circuits and the size of the power feed wire and the quality of the connections, you can have one or more volts drop from the battery to the dash mounted volt gauge. This is basically what Chad stated “You may just have too much resistance in the wiring that feeds the ammeter/voltmeter in the car. A loose connection, corrosion, or just old wiring.”

Also the volt gauge is no longer an indication of charge or discharge conditions as it is not measuring current flow into or out of the battery. It now measures the voltage applied to the dash gauges, if it is on the charge side the voltage is higher than 13V if on the discharge side the voltage is less than 13V.


Measure the voltage at the fuse that feeds the dash mounted volt gauge let us know if it agrees with the dash gauge.

Hope this helps

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Discussion Starter #7
Elree and Chad.... both...

Thanks for all the help. I'll check the voltage at the fuse block and now that I am reminded that midpoint is 13V I won't worry about this as much.

I will post what I find so that anyone else following or using this thread later will have the whole story.

I just got a handheld voltmeter so I am just learning how to use one. It is a cool tool!

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I want to die in my sleep like my grandfather...

68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28, less than 14,000 miles on it!

Not screaming and yelling like the passengers in his car.
 

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Discussion Starter #8
Elree Colby, the guage is reading right on with what you indicate. I did a bunch of testing today and found the alternator is not putting out consistent voltage. Sometines at 14 volts and most of the time it reads the same as the voltage at the battery indicating to me that it isn't putting out anything.

Am I right in my analysis? I believe I have a new alternator that isn't working properly.

It seems to stop working when I put a large load on it with turning on the headlights, A/C and mega watt radio. Once it stops working at 14 volts it usually does not start putting out voltage above 13 volts.

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I want to die in my sleep like my grandfather...

68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28, less than 14,000 miles on it!

Not screaming and yelling like the passengers in his car.



[This message has been edited by Redrum (edited 09-28-2002).]
 

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Mike

If you have a multi meter connect it to the alternator output and a good ground, position it so you can read it from inside the car, get in the car rev the engine and turn on the headlights, the A/C and the mega blaster. Post back the volt reading. Also what’s the amp rating if the alternator?

What you’re seeing may not be a bad alternator. Your dash mounted volt gauge is reading the voltage at the fuse block, I don’t know how the painless wiring gets power from the alt/batt, however as the load on the power supply wire increases the voltage at the block will decrease, depending on the size of the wire and the length. This could explain the low reading on the gauge. How does the fuse black get power and what size is the wire? Also how is the alternator connected to the battery?
 

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Discussion Starter #10
I will try to get the readings on the voltage next weekend. The fuse block is fed by a 10 guage wire from the battery with a 50 amp fuse about 18 inches from the battery.

The alternator feeds to the battery side of the 50 amp fuse and via a 10 guage wire into the Painless harness near the fuse block.(Two 10 Guage feeds off the alternator.) The alternator is rated at 107 amps.

The sound system pulls directly from the battery via a solenoid controlled by the radio.

Elree, I have just basic knowledge of wiring and quite frankly there may be absolutely nothing wrong other than my not knowing what I am suppposed to be seeing. No dead battery or anything to indicate a problem other than what I beleive is low voltage showing at the guage.

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I want to die in my sleep like my grandfather...

68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
97 Z-28, less than 14,000 miles on it!

Not screaming and yelling like the passengers in his car.

[This message has been edited by Redrum (edited 09-29-2002).]
 

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Mine drops at the gauge too when I turn on the lights, electric fan, etc. No charging problems though. The lights dim slightly when I turn the fan on, but that's because they're fed through the fuse-box rather than via relays from the battery. I have the parts but I'm too lazy to spend ten minutes hooking up the relays.

I think everything's fine with your charging system.

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My Web Page (updated 06-21-02)

"Long Live Freedom!"

Chad Landry
TC Member #643
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'68 El Camino
 
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