Over the years I have owned several C-3's. I had a 71 that I owned for quite a while. Suddenly it developed a momentary flutter of the ammeter at the first touch of any electrical use. Otherwise all was fine. I never had any electrical problems after that but it always did the little momentary flutter. About a year ago my 69 began doing the exact same thing. Today it started to flutter at idle fairly constantly and also at random just cruising. This is not a wild extreme flutter just a very rapid flutter that I would guess to be about 10 per second and about 10 amps on either side of "0". I charges fine and shows load fine ... Just annoying and the fact that It did not do the until today. Any Ideas? :confused:

 

Silver, my '72 has been non stock in various dash/panel instrumentations for so long, I can't remember...BUT....do you have a red dash light...alt/bat/gen marked??? does it flutter??? if you don't have any dash light....I really don't think I ever did, and in fact I can't find one on my factory service manual wiring diagram....and that terminal that would go to a failure light is shown as going somewhere that makes NO electrical sense at all....

I just occured to me...you have an external regulator...NO??? if you do you need adjust the contactor relay inside the regulator...by loosening a bolt on the relay armateur and sliding it in and out...to reposition the amount of energy it takes for the thing to close/open.....

I was thinking of an internal regulator alternator.....

GENE

 

69 was the first year to use internal regulators... but only on Corvettes. No I don't have any light, just the stock ammeter. I have had some corvettes that never did the flutter and two that started doing it while I owned them.

 

Silver, just a thought...how old is your battery? All the cars I have driven over the years (non vette included) I have experienced some odd electrical problems just before the battery expired. Weak cell , short in the battery case, poor ground ???? I have had diodes blow in the alternators, boards go bad, etc due to bad or weak batties batteries.
Good luck Mark :cheers:

 

The Battery is almost three years old... It is an Auto Zone three year FREE replacement so it's about time to exchange it. They never Question you like some places do.

 

Silver, assuming battery voltage is good under carnking load...ie, not less than 10.5 volts....should be 11.++ volts....i'ts fine....

I suspect you have some of the symptoms I had with my alternator/eletctricals....that is to note the amp meter in fact is connected in series with the sense wire....the other terminal is in series with an alt/gen/bat red light on the dash...the positive side of that light is a SWITCHED source, not steady....unlike the ampmeter feed is allways on...and goes through the ampmeter to the sense input of the regulator....

What happens, I found is eliminating that light bulb from the vettes, makes the factory stock internal regulator somewhat unstable....both as to specific charge cut in at lo rev's and also staying in the charge mode....
with a dash light in series with that light indicator wire....it will light when the ignition is on, engine still....crank up, light goes out...BUT still voltage at the regulator...going through that bulb...it's part of the sense circuits....along with the other one through the amp meter.....really, they BOTH need to be there....
in fact you will find that is the way most other cars of the era were wired....
beleive me, I finally took the time one day to prove all sorts of things with the SI17 style 2 pin internal regulator alternator series....they come in all sorts of ratings, but the regulators are the same.....externall hookup wise anyway.....and the behavior of them is unstable without correct hookup...
that is why a 'one wire' alternator takes a fair amount of rev's to start charging, and in fact will drop out at idle sometimes...depending on load....
the one wires were ment for simple marine hookup in a screened in arrangment for gas fumes.....and are not really all that good for auto use...

GENE

 

Next time it does it turn on some lights(interior or headlights) and watch them. If the lights flutter too than it maybe the alt , battery, lose connection. If they don't, than my guess would be a bad ammeter or a lose connect to the ammeter.

 

There is no electrical flutter or problems. Just the ammeter flutter. Voltage ranges between 14.2 and 14.7. Except starting of course.


[Modified by silvervetteman, 5:37 AM 4/7/2003]

 

My '69 did the same thing, after chasing electrical connections throughout the car, for months!, it ended up being one of the wires going into the plug on the side of the alternator. It had a hair line crack through the solderless connector, that i did not find until it finally broke in two and stopped charging altogether. There are two wires, one flashes the field for the voltage regulator and the other is the input, tells the voltage regulator what the voltage is so it knows what to do, it was that one. I'm guessing that it would heat up or vibrate open and i would overcharge(momentarily) then it would close, and I would undercharge, this would happen very rapidly though creating the fluttering like you explained. For me the fix was twofold, repairing the bad wire and replacing the alternator afterwards since the fluttering damaged the voltage regulator. now two years later no more fluttering. ok, actally a year and a half since the car is apart for a motor/tranny/rear end at the moment.

 

I just spoke to an electronics engineer at work today(also a C-3 owner). He said there is a filter capacitor on the amp gauge that is bad. If ( and mine does) the gauge flutters at the onset of a load without the engine running that would varify that the capacitor is fualty. So when ever I have the center cluster out I know what to do. Thanks for all of the input.

 

Silver...can you replace just the capacitor or do you have to replace the gauge? This has been an interesting thread!!!!
Mark :chevy

 

According to my friend, you can replace the capacitor. He thinks there may be a resitor there also but it sound like it is OK. Yes this has been a good thread since I had another car that did the same thing and I never solved it. (don't you hate that?)