Help

[Donw]

I was wondering if anyone can help me/ I have a 1969 corvette convertible 350/300. When idling the amp meter stays around 0, when I step on the gas it goes to a -40. Any ideas why.

 

[srs244]

it's been a long time since i had my 69 convert, but without knowing if this is something that just started to happen, or you just got the car and noticed this, most of us would be just guessing. it could be anything from having the gauge wired backwards, to a short or ground condition. the entire charging system passes throught that amp gauge.

 

[Donw]

It has been mostly since I had all gauges rebuilt and I installed. What I don't understand id why it only happens when I push throttle down?

 

[68Roadster]

Don,
I'm having basically the same problem on mine except that when I push the throttle down mine goes to +40......I have checked the complete charging system wiring for shorts to ground. After running for awhile the guage calms down and moves less with throttle movement. Mine started this after a bad jump experience that fried a fusible link. I have replaced the voltage regulator, the link and checked the ground underneath the battery box. It is definitely a weird problem that I woudl like to have fixed. I don't want to cook the battery by overcharging it.
I can't remember what hooks up to the ampmeter but I would check the connections, almost sounds backwards.
Let me know what ya find. Do youhave wiring diagrams for the car?

 

[Donw]

yes I do, I will check color of wires to terminals again.

Thanks

Don,
I'm having basically the same problem on mine except that when I push the throttle down mine goes to +40......I have checked the complete charging system wiring for shorts to ground. After running for awhile the guage calms down and moves less with throttle movement. Mine started this after a bad jump experience that fried a fusible link. I have replaced the voltage regulator, the link and checked the ground underneath the battery box. It is definitely a weird problem that I woudl like to have fixed. I don't want to cook the battery by overcharging it.
I can't remember what hooks up to the ampmeter but I would check the connections, almost sounds backwards.
Let me know what ya find. Do youhave wiring diagrams for the car?

 

[srs244]

one thing that might be confusing you is the difference between a volt guage that is now being used (which is an indication of battery condition) versus an amp gauge which is a rate of charge indicator. if you sit at idle for a bit, you aren't charging your battery on an older car. in most cases you are probably actually discharging it a bit. therefore when you accelerate and your increase the revs to the alternator/generator, the voltage regulator will be open and show a greater rate of charge. once the regulator senses that your battery is getting closer to full charge, it cuts back the rate of charge, there by reducing the indication on the gauge. please understand that the above is a non technical explanation of the charging system, but does describe in very basic terms what you are looking at on an amp gauge vs a volt gauge.. it should show a greater rate of charge after starting your car or after sitting at idle for a bit, and then "settle down" as you described because the rate of charge is diminished at that point.

steve

 

[JohnZ]

The "ammeter" in a post-'62 Corvette isn't an ammeter at all, and none of the charging system current goes through it. It's simply a sensitive voltmeter with two inputs - one from the horn relay buss power junction, and one from the battery cable stud on the starter solenoid; all it does is measure the voltage difference between those two points and display it as "amps" to show whether current is flowing TO or FROM the battery.

If it goes to -40 when you nail it, it's most likely a wiring problem or loose connection somewhere that's affected by engine torque/movement.

 

[Donw]

Steve,

What mine is doing is when I step on the gas in shoots straight over to -40 like a direct short but only when I step on the gas. That is what I don't understand. I would think it would move right to show charging?

Thanks

Don