Topic: twitchy ammeter
in Forum: C3 Electrical
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The ammeter on the 69 is a bit twitchy. It reads around zero on average, but twitches to + or - 20. I haven't done much diagnosis except to check that I have 15.1v directly off the alternator while this twitching is going on. Its not killing batteries so thats good. Anyone have this symptom before and know what it is or where to start?
Phil
Phil
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Could be a loose connection at the gauge, or the firewall/fusebox junction. There is also a resistor on the back of the gauge that is supposed to keep it steady. The resistor may be flaky, or loose.
Is it a really quick blip, or does it sorta bounce?
Is it a really quick blip, or does it sorta bounce?
Joel Adams
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What I should've axed was, is it a constant up/down bouncing, or does it just have a quick little blip every now and then?
Even tho you may see a steady reading at the alt with a voltmeter, you could still have a problem with the alt, such as an A/C ripple, or brushes that are nearing the end of their useful lives. A voltmeter, especially a digital meter, will show an "average" of the voltage, but not peaks(hi/low), unless your meter will graph.
I'd check all of the connections, at the alt, batt, and grounds, to make sure it's not just a loose connection first.
Joel Adams
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[QUOTE=Adams' Apple]
What I should've axed was, is it a constant up/down bouncing, or does it just have a quick little blip every now and then?
Even tho you may see a steady reading at the alt with a voltmeter, you could still have a problem with the alt, such as an A/C ripple, or brushes that are nearing the end of their useful lives. A voltmeter, especially a digital meter, will show an "average" of the voltage, but not peaks(hi/low), unless your meter will graph.
I'd check all of the connections, at the alt, batt, and grounds, to make sure it's not just a loose connection first.[/QUOTE]
What I should've axed was, is it a constant up/down bouncing, or does it just have a quick little blip every now and then?
Even tho you may see a steady reading at the alt with a voltmeter, you could still have a problem with the alt, such as an A/C ripple, or brushes that are nearing the end of their useful lives. A voltmeter, especially a digital meter, will show an "average" of the voltage, but not peaks(hi/low), unless your meter will graph.
I'd check all of the connections, at the alt, batt, and grounds, to make sure it's not just a loose connection first.
[/QUOTE]
Joel's right a lot of electronics nerds(myself included) prefer the needle/analog over the digital display. They are more sensitve and easier to read for drops or spikes in voltages, unless you got an O-scope handy that is. If the gauge is giving you a good baseline reading and your seeing the needle bounce the gauge might be allright.
Turns out it appears that is was a bare spot on the starter cable. Insulation had been worn through by a clip that holds the cable to the starter solenoid. I suspect it may have been arcing to the body of the solenoid. Temporarily, I have taped it up and put some split loom over it and ever since, the ammeter is rock steady. Guess I ought to order a new cable.
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Member: NCRS, NCRS Texas, Corvette Legends of Texas
New cable, or some means of insulating it...don't wanna hafta call the fire department!
Glad ya found the problem, anyway!!
Joel Adams
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in Forum: C3 Electrical
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