Ammeter Discharging

[Gerald C.]

When I started my 63 the ammeter would jump all over the place. I replaced the voltage regulator and the needle settled down. Now when I sound the horn or put the lights on, the needle pegs to the negative 40. Is this an alternator problem or a bad cell in the battery. I've heard both.

Thanks,

Jerry

[Wayne P.]

Re: Ammeter Discharging

I doubt it would start if the battery had a bad cell.

[Gerald C.]

Re: Ammeter Discharging

Wayne,

So my other option to look into is the alternator?

Jerry

[Jack H.]

Re: Ammeter Discharging

The voltage regulator plays the role of 'traffic cop' for the charging system by looking at the battery's current voltage level and instructing the alternator to turn ON/OFF to pump the battery back to a fully charged condition. If the voltage regulator lacks a good ground, it can see things that "ain't" and issue erratic orders.

My advice is to stop trying to diagnose by randomly swapping parts. Each time you touch/move a component, you're also jiggling the attached wiring harness making it possible for problem(s) to come and go....

Try taking the car to a competent auto electric shop where they'll roll out their charging system diagnostic car and look at ALL of the charging system's parts in-car. Expect a good electrical tech to fault diagnose the system in 15-20 minutes flat and save yourself a lot of hair pulling!

[Stuart F.]

Re: Ammeter Discharging

But Jack, that takes all the fun out of it. These are our Vettes, our babies, and back in 63 we didn't just run down to the corner Electrical Tech expert just because we had a bouncing ammeter needle!

You are probably right. That's the way he should proceed. Over the years, I've changed out voltage regulators and rebuilt my Alternator and if I had any concern it's that my needle doesn't move much at all (+ or -). But, the car runs fine and the battery is always there for me even if the car sits for a few weeks with the trickle charger on it. The lights work good and strong at night too.

If you don't feel confident to troubleshoot the system yourself using the basic instructions available in the service manual and in many other publications, as well as the usual great advice you get here, then by all means go to a pro.

Stu Fox

[Gerald C.]

Re: Ammeter Discharging

Thanks everyone for your advice. I'm going to a service station where they can check the system.

Jerry

[Duke W.]

Re: Ammeter Discharging

A multimeter is a basic item in any enthusiast's toolbox. You can troubleshoot virtually any vintage Corvette electrical problem with the cheapest versions. I picked one up at Harbor Freight recently for about eight bucks to add to my "collection". It was too cheap to resist!

With the battery fully charged and the engine off the battery voltage should measure about 12.5v at room temperature.

With the engine idling and all accessories off voltage at the battery terminals should be in the range of 13.5 to 14.5 volts. If not in this range there is a charging system problem, which requires troubleshooting and further troubleshooting is in the appropriate GM shop manual/chassis service manaual for your car, which should be in your library.

Duke

[William C.]

Re: Ammeter Discharging

Since the ammeter (a misnomer) is actually detecting voltage drop across two ends of a wire, I would suspect a poor connection at one end of the wire or the other. You have an 18ga black wire that goes thru the connection from the back of the fuseblock to the engine compartment, and then goes to the battery feed to the starter at the solenoid. The second wire, 18 ga red goes thru the connection behind the fuseblock into the engine compartment and ends up at the horn relay. I'd check the connections all along the path just described before getting too carried away with esoteric theories. Mine is that the connection at the horn relay is not good and the horn relay feed that should be coming from the 12 gauge red wire is partially coming thru the ammeter wire, a real god way to burn up the ammeter.

[Gerald C.]

Re: Ammeter Discharging

Okay everyone,

I put a new regulator in and had the alternator cleaned & tested. Yet the battery doesn't change voltage when the car is running. In addition, if I step on the brake or sound the horn, the ammeter discharges. The closest electric shop is about 45 minutes away so that might be my next visit.

Any thoughts on where else to look at home?

Jerry

Okay everyone,

A put a new voltage regulator in and had the alternator cleaned and tested.

[Ken A.]

Re: Ammeter Discharging

Gerald,
63 & 64 Corvette ammeters are notorious for a "happy" pointer, i.e., jumpy needle. Sometimes they'll just flip over & be upside down. The cause is that the silcone damping fluid that was originally in the gauge to dampen the movement, has long ago dried up or drained off. There are 2 solutions. First, find a good gauge guy who has the special tool to reinstall some grease (also works well on electric tachs). That MAY fix your problem. Second, you can always buy a new repo gauge that will be good for many more years. Hope this helps.

[John H.]

Re: Ammeter Discharging

Is the black/white tracer ground wire attached to the base of the voltage regulator? If it isn't grounded, it won't work.