Flickering alternator gage.

[DanEC]

I went for a ride this morning and the car drove fine except for a couple odd flickers of the amp gage. Once the car was warmed up and the battery back up fully from cranking, the gage typically holds steady at a very slight charge with the parking lights on. But I noticed while driving along an occasional flicker to -50 and back - very quick, hard to catch and only one flicker. And then it will be several minutes before it happens again. Not doing anything but motoring along. I noticed it 3 times this morning in a 15 mi +/- drive but it probably happened several times when I was looking away.

I was once told on one of my old Mopars that any discharge flicker on the amp gage was a likely a momentary short somewhere in the harness/system. In the case of my 66 Satellite this was probably right as I found a melted harness section from the alternator to the bulkhead box. So that has me worried. It has a standard 60s era alternator replacement on it - nothing high-amp.

Everything looks good on the harness to the fuse box. I had to replace the alternator and big orange wire between the fuse box and alternator several years ago because of a loose connection at the alternator that partly fried it and melted the alt insulator. But never blew a fuse. I think I put an electronic VR on it but may have to go back to confirm.

Reason to worry?

[patrickt]

Originally Posted by DanEC

Reason to worry?

Of course it's a reason to worry. Whatever it is, it will only get worse and it will get the worstest of worse at the worst possible time.

First things first, did the momentary swing to the -50 possibly coincide with the thermostatic puller fan coming on?

[DanEC]

My memory kicked in about 10 minutes ago - yes the HD cooling fan. I’ve spent the last year working on the old 66 Satellite and haven’t driven the ERA enough to stay familiar with it.

So - you’re right - NEVERMIND. Absent mindiness.

Thanks

[patrickt]

Originally Posted by DanEC

So - you’re right - NEVERMIND.

Man, if I had a nickel.... Anyway, if you're taking 50+ amp momentary spikes through that old Smiths amp gauge consider adding a parallel 12-gauge line from the protected side of the large circuit breaker next to the starter solenoid over to the passenger side screw of the #1 fuse (the one controlling your fans and to where the other side of the amp gauge is wired). This will lightly suppress the spikes through the ammeter and act as a dynamic backup for the entire charging circuit. Should the ammeter start to fail and begin to exhibit increased resistance, current will automatically shift over to the lower impedance path. The hotter the ammeter gets, the higher the resistance, the more the current gets shifted over to try and save the day. The ammeter will continue to tell you all it did before adding the parallel line, just at a more muted pace. That little task will take you about an hour to do. Now, if you happen to have the pusher fans as well, and if you happen to have all three wired in to come on at the same time, then that ammeter needle can swing over so hard that it gets stuck and you have to whack the gauge with your knuckle to make it come back. The first time you see one of those you'll think the needle fell off the gauge and is down at the bottom, but no, it's still there. You just can't see it.

[DanEC]

The big jumps are to -50 when the fan kicks in. I saw one quick jump to the + side about half way I would guess. That’s probably when it shuts off and takes a split second for the VR to adjust.

Got a schematic of that wiring - specifically of the protected side of the circuit breaker near the starter relay? I’m going back out now to finish up an oil change and I’ll look at it to see if I follow that?

[patrickt]

You could actually test out the modification with two feet of twelve gauge wire with alligator clips on each end. Clip one gator end on the top post of the circuit breaker over by the starter solenoid and the other end on the passenger side clip of the #1 glass fuse. Then just drape the wire behind the engine so it's not in the way of anything (like maybe the throttle linkage). Then drive your car around for a weekend and see if you like the new behavior of the amp gauge.

[sunman]

I’m really HiWatt Wyatt all the other guys in “The Fabulous Yellobellies” are taking a big dirt nap.
You do have a 100-0-100 gauge, rite? Spike amps get kinda high
I run a twin Ampeg SVT with 8-10 cabinets rig

Party On

[PDUB]

Originally Posted by sunman

I’m really HiWatt Wyatt all the other guys in “The Fabulous Yellobellies” are taking a big dirt nap.
You do have a 0-100 gauge, rite?
I run a twin Ampeg SVT with 8-10 cabinets rig

Party On

Eden Highwayman WT-500 with 410XLT/410XST... or 210XLT/210XST for smaller venues... or 210XST for intimate venues.

[sunman]

PDUB! of course now it all makes sense. Gotta love it

[DanEC]

Originally Posted by patrickt

You could actually test out the modification with two feet of twelve gauge wire with alligator clips on each end. Clip one gator end on the top post of the circuit breaker over by the starter solenoid and the other end on the passenger side clip of the #1 glass fuse. Then just drape the wire behind the engine so it's not in the way of anything (like maybe the throttle linkage). Then drive your car around for a weekend and see if you like the new behavior of the amp gauge.

Got it - top screw post on the relay and over to pass side of #1 fuse. May be a few weeks before I can try it out but I’ll try it and see what happens. What should I expect to see - just smaller flickers in the gage?

[patrickt]

Originally Posted by DanEC

Got it - top screw post on the relay and over to pass side of #1 fuse. May be a few weeks before I can try it out but I’ll try it and see what happens. What should I expect to see - just smaller flickers in the gage?

It will still show you charging/discharging conditions pretty clearly, but the in-rush current surge for inductive loads (like your fan motors) won't catch your eye as much with large needle swings. You'll still notice them if you're looking at the gauge but they won't be as dramatic. The action of a 12 gauge shunt wire though will help protect the ammeter from overheating, which creates more resistance, which creates more heat, which creates more resistance, which creates a bad day under the dash. There is no down side to adding the shunt unless after doing so you say "my ammeter doesn't even work now." I don't think that will be the case though. If that did occur it would mean there was unusual resistance in the ammeter gauge and line itself and now most of the current is choosing the shunt line because it is the path of least resistance. I don't think that is the case but you would know fairly quickly. In fact you wouldn't even have to start the car. Just clip the alligator leads on and then turn your headlights on. You can compare the "shunting effect" by looking at the ammeter with the headlights on, and the engine not running, and then remove one alligator clip and see how the needle changes. The change in the position of the needle is the result of the shunt.

[strictlypersonl]

With high output alternators, I recommend a shunt wire to bypass about half the current going through the ammeter. You just must remember that the ammeter isn't showing the true current. Frankly, that's really not that important. The direction of current is.

[DanEC]

Bob - I’m just running a standard alternator, nothing high powered. By a shunt are you meaning the same thing that Patrick has described as a shunt - #12 wire from top connection on the circuit breaker next to the starter relay and over to the pass side of the fan fuse?

[patrickt]

Originally Posted by DanEC

Bob - I’m just running a standard alternator, nothing high powered. By a shunt are you meaning the same thing that Patrick has described as a shunt - #12 wire from top connection on the circuit breaker next to the starter relay and over to the pass side of the fan fuse?

Yes, we're both saying the exact same thing. 12-gauge wire and shunt are the same thing.

[DanEC]

Took a long time to get the car out again - 100 F temps and family - but drove it today. The shunt tamed the wild jumps and needle flickers when the lights were turned on, turn signals activated and that big HD fan kicks in. You can barely see a little twitch in the needle now. A great change - I hated seeing those heart stopping needle dumps every time that electric fan kicked on or off.

[patrickt]

... not to mention extending the life of that POS ammeter.

[DanEC]

That’s probably worth even more.

[patrickt]

Originally Posted by DanEC

That’s probably worth even more.

And the beauty of the shunt is that, should the ammeter start to fail, the increased resistance in the ammeter path will cause more current to automatically shift over to the shunt path, thus reducing the heat in the ammeter. Slowly, but perceptively, the ammeter will start to show less movement, then it will roll over, cough, sputter, circle the drain a few times, then pass on into the great automotive electronics scrap heap in the sky, yet your car will continue to putter on down the road.

[ERA174]

DanEC, If you’re enamored with your ammeter then disregard the following. The ammeter is a weak link in the electrical system and a potential for failure and possible electrical fire. patrickt & strictlypersonl have given you ways to decrease the current seen by your ammeter, thereby minimizing the potential for failure. Another avenue is to eliminate the ammeter and replace it with a voltmeter. If the voltmeter fails, potential for severe electrical system failure and fire is significantly reduced. The ERA owners link has a section that specifically addresses the ammeter to voltmeter conversion, should you decide to go that route.

[DanEC]

Thanks ERA174. Unfortunately I have 4 old cars (if you count the Cobra as old) and all of them have an ammeter gage in them (2 Mopars and an old Vette) and all are known for the same hazard. If I were to start changing them all out to Volt meters, as slow as I am it would be a big project. I’d probably start with my 67 GTX which still has 100% original harness, and everything still amazingly works (which probably is some sort of miracle or record).