I have a 67 350-hp conv. that shows ammeter fluctuations. With the headlights on and the engine at idle, the meter shows -15 to -20 amps depending on what additional load is on(brakes,heater fan, etc.). At higher rpm's it will show +5 to + 7 for a minute or two and will then settle to 0. The meter will sometimes spike or dip at higher rpm's with associated brightening or dimming of the headlights(this really worries me). With the lights off and at high rpm's the meter will show 0 after a minute of +5 charging, but will dip below 0 at idle. I have replaced the alternator(x2), volt. regulator(x2), battery, starter, engine and headlight wire harness, headlight switch, and had the ammeter checked for correct function. Is all this normal? Any suggestions? Thanks!
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Re: 67 ammeter fluctuations
Steve,
You may just own the only Corvette in existance with an ammeter that works properly! If there is no associated over/undercharging of the battery, buring out of bulbs or other signs that you have a charging problem, it might just be that everything is just fine.
Mike
Quebec NCRS Chapter -
Re: 67 ammeter fluctuations
Had same problem with mine. Turned out to be a bad ground connection at the votltage regulator. Good LuckComment
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Re: 67 ammeter fluctuations
Mike and Brian, thanks for your responses, I will check the ground at the regulator. Mike,as you questioned, there is no bulb burnout or battery charging problem(although I do not drive at night much) so all may be ok. I was thinking of "modern cars" that have ammeters that show +12 to +15 amps when driven.Comment
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Re: 67 ammeter fluctuations
Have you put a volt meter on your car, with the engine running, to see what is going on? Obviously, with an external voltage regulator you can't easily pull the alternator out to have it tested. The starter/alternator shop near me put my alternator, while it was in the car, through it's paces several years ago when I was having troubles with battery charging. I would start with as much of an on-the-car diagnosis as you can find in your area.
This discussion board has had plenty of cussing and discussing about mid-year ammeters and all of the problems that we have had with them. Gary 66 327Comment
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Re: 67 ammeter fluctuations
Steve, make sure that the capacitor that attaches to one of leads is properly installed,because without it the ammeter tends to fluctuate dramatically in its readings. Just a thought... KieranComment
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Re: 67 ammeter fluctuations
Steve,
Now you know why Chevrolet (and every other manufacturer that I know of) quit using ammeters, nobody could ever explain to the customer how they worked! I agree with Mike, your ammeter is working. The "spiking" is probably a loose connection or intermittent ground as Brian suggested. Remember these old cars have external regulators that are electro-mechanical devices. If you ever open one up you will notice it has little coils with breaker points connected to them. It is the opening and closing of these points that decide how much and how often the alternator sends power to the battery. Check the condition of the points inside the regulator, if they are burnt and pitted, clean them up with a point file. Be careful, if you get these out of whack, you'll be calling John Pirkle for a new regulator! When you said "..."modern cars" that have ammeters that show +12 to +15 amps" you were confusing an ammeter with a voltmeter. A voltmeter will usually show 12-15 volts, not amps. And that is why manufacturers went to voltmeters, they always show 12-15 volts. Even when the alternator is fried and the battery goes dead they show 12 volts! Good Luck.Comment
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Re: 67 ammeter fluctuations
Typical ampmeter readings on a 67 would be zero or slightly + after the car has run for a few minutes and the battery is at full charge. A quick test is to discharge the battery for a few minutes by leaving the lights on. Then start the engine and watch the meter. It should charge at 20 or 30 amps for a time slowly falling back to zero after full charge is achieved. This should be done at 1000-2000 rpms. Another check for regualtor function would be to turn the lights on while the engine is running and watch the guage there should be an instantaneous drop in guage with a quick return to zero.Comment
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Brings up a good question-
Does anybody recall an ammeter or voltmeter or idiot light indication that ever told them of an impending problem?
Or is it the classic case of adding insult to injury AFTER you know that the car is broken?
Mike
NCRS Quebec chapterComment
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Re: 67 ammeter fluctuations
Along to Mr. Schisler's excellent advice I would add:
Consider checking (with an digital multimeter ammeter) the current actually being sent to the ammeter. I had (here comes the heretical part) a difficulty with my 1966 Mustang intermittantly pegging the guage in an asyptomatic car. After tracing the wiring (and finding nothing amiss), it appears to have been a "therapeutic disassembly" since is not working properly.
When my 1967 ammeter failed, it would "flutter" (high-frequency oscillation) about the neutral marking at idle.
Good luck!
CarlComment
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Re: Brings up a good question-
Many times ampmeters can give indications of lurking demons. You need to be familiar with symtoms though. For instance, after a moderate pull down, if your ammeter shows only a slight charge and returns to zero after a very short time where it used to charge hard for a few minutes before droping back, its a sure sign of a dying battery.Comment
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