67 Ammeter Question

[Al P.]

Up until 2 weeks ago my "Battery Meter" was working fine - when battery is charged and driving it would be 99% Straight Up on "0". Very small movement to the right.

Now when Im driving its over to the right to the first line. Thinking it was the battery I bought a new one and regulator as well. No change. Reads high even thought the battery is fully charged.

The charging system is perfect (I have a volt guage as well) at 13.8v when running. Alternator is fine as well as the battery gets 13.8 - 14.0 v when warmed up and running.

All gounds are good, everything checks out fine. No loads on battery when parked as well. The guage is stright up when parked.

I have read that these guage have dampeneing in them and they do go bad - So I am hedging towards a new guage to see if it is the problem.

Has anyone seen this issue? Any advice? Thanks!

[Joe R.]

Re: 67 Ammeter Question

The dampening system in the gauges just keeps them from oscillating from bumps and surges in current. Has nothing to do with reading correctly or incorrectly.
The gauge could be going bad but I would recommend you clean the connector on the back of the gauge and also clean the contacts at the firewall connector. Corrosion can cause high resistance and deflect any gauge.

JR

[Domenic T.]

Re: 67 Ammeter Question

Al,

My gage burnt out back in 71 and I rewound it with the same size wire and turns.

It did it again as I did not find the sorce of the problem.

Then I found a bad ground on the cluster and the problem went away.

I don't have the schematic in front of me but a lot of problems on fiber glass built ends up a bad ground.

So to add to what Joe said I would also check the ground also.

DOM

[William C.]

Re: 67 Ammeter Question

Actually, the ammeter in the 63-67 cars is actually a sensitive voltmeter that measures voltage drop across a length of wire running from the regulator to the starter solenoid as I recall. (I can check the prints if anyone needs the exact info) This is very susceptable to any dirty connections, especially those found at the pass-thru connections from the engine compartment to the drivers compartment, right behind the fuseblock. I'd start looking for connection issues there. Remember you are measuring a TINY voltage drop across an approximately 5 foot length of 12 gauge wire. It is a very sensitive system.

[Al P.]

Re: 67 Ammeter Question

Everything works fine except the ammeter (bat guage) that is reading high before at start and after start -

This started 3 weeks ago - I have replaced the guage, Energizer Battery, Alternator, regulator........Same result....

Its making me crazy! I have a volt guage in aux cluster under dash, that read 14vdc on the nose when the car is running - no issues there. The battery shows 12.86 when car is parked so the new battery is quite good. When car sits idle parked the guage needle is straight up as it should be.

I put a digital ammeter betwen the ground lead of the battery (in series of gnd cable to car) all loads when parked and it read "00.0" - NO PARISITIC LOADS - which is perfect....

So I am trying to figure out and correct why the battery guage now reads high in both drections? I want to fix it ASAP

[Al P.]

Re: 67 Ammeter Question

I checked bot leads to the meter - Each wire reads correctly.

When car is idle they are the same as they should be - guage is straight up - as it should be.

When any accesory is turned on - like turning lights on car not started -the battery guage reads twice as much to the left as it used to

And the same - high readings to right when car is running. Voltage to battery is 14.0 (perfect). Battery standing is 12.86 - fully charged.

Everything still working fine in the car - no issues - except for the high readings on this one guage.

Before this started, when motor running the meter was alwways straight up. Now it runs between 20-40 amps all day long. But battery is only seeing 13.8-14.0 volts. So go figure?

Battery Guage Used to work perfectly until 3 weeks ago.

Does the same with the new guage I just purchased. I replaced every component in the charging system as well.

Next test - I will discconect the present wires to the existing guage and run 2 NEW wires to my spare guage and see what happens.

Please note that you dont even have to start the motor to see this issue. Just turn anything on while the car is parked and the readings to the left are way high...it was never like this until 3 weeks ago. The battery in the car is new and fully charged. I have had three diff batteries in the car and the results are always the same as indicated.

Im thinking of adding a shunt resistor (.1 Ohm) to the guage to see what occurs then - I read about this in earlier posts in the archives.

From the archives:
From Archived Posts:

"it can be noted that the ammeter reads the difference in voltage between the battery and the alternator. The wire that goes directly from the battery to the alternator and appears to short out the ammeter is a meter shunt. What the ammeter actually reads is the voltage drop across this wire. The resistance of this wire is about 0.1 ohm. There is no physical resistor in the circuit, the resistance is due to the length of the wire required to get from the starter solenoid to the horn relay around the engine bay."

[William C.]

Re: 67 Ammeter Question

OK, but it's not really an ammeter. If you do a search on voltage regulator midyear, you should find several posts that explain the "ammeter" in a C-2 is really a sensitive voltmeter that measures voltage drop across the ends of a 12 gauge wire. What your gauge is telling you (assuming the meter itself is to spec) is that it is seeing a higher than "normal" voltage drop across that length of wire. Could be a bad connection at either end, bad ground or similar issue, but you are really seeing voltage drop that is calibrated to mimic an ammeter function. The fact that the reading is off equally in both directions would lead me to look for a bad (high resistance) connection in the sensing circuit.

[Wayne W.]

Re: 67 Ammeter Question

Sounds like its working right now and wasnt before. It will take a very long time to fully charge a new battery. When that occures, the gauge will center like it should.

[Al P.]

Re: 67 Ammeter Question

Sounds like its working right now and wasnt before. It will take a very long time to fully charge a new battery. When that occures, the gauge will center like it should.

The guage was always working, but now it reads high all the time......

The battery is brand new and fully charged - it sits idle at 12.86 volts. I had 2 other batteries in there already all fully charged and the same results. This is not a battery issue. When car is running voltage on battery is 14.0 volts - charging system is working.

The needle does not come near the center when running - its reading high all the time both when car is running or not running. High in BOTH conditions.

This must be a wiring issue. I'm going to rewire the ammeter with new 16 gauge wires as shown in the schematics and go from there. The gauge is good.

[Wayne W.]

Re: 67 Ammeter Question

When you say it reads high all of the time, does that mean it reads in the positive all of the time? Even when the switch is on, but the engine is not running. Does it go negative when things are turned on when the engine is off?

[Joe R.]

Re: 67 Ammeter Question

The guage was always working, but now it reads high all the time......

The battery is brand new and fully charged - it sits idle at 12.86 volts. I had 2 other batteries in there already all fully charged and the same results. This is not a battery issue. When car is running voltage on battery is 14.0 volts - charging system is working.

The needle does not come near the center when running - its reading high all the time both when car is running or not running. High in BOTH conditions.

This must be a wiring issue. I'm going to rewire the ammeter with new 16 gauge wires as shown in the schematics and go from there. The gauge is good.

Al,

Check out this article, it has info on the ammeter circuit and more:

http://www.lbfun.com/warehouse/tech_...g%20gauges.pdf

Good luck and may the force be with you!
Joe

[Al P.]

Re: 67 Ammeter Question

When you say it reads high all of the time, does that mean it reads in the positive all of the time? Even when the switch is on, but the engine is not running. Does it go negative when things are turned on when the engine is off?

1.When the car is parked - the gauge is straight up - centered as it should be (Normal)

2. When the car is parked and you put on the lights or any accessory it swings way left almost to -30-40 (it never used to do this - it would go a little to the left around -5 to -10

3. When the car is running with battery fully charged it varies between +40-+20 and sometimes comes closer to middle - high all the time. (It always used to run straight up when battery was changed and driving the car). Now it reads high and it should not do that. Something changed around 3 weeks ago - Everything is the car working perfectly and charging system is good.

[Wayne W.]

Re: 67 Ammeter Question

By chance have you added something electrical, fan, radio, etc.? It does sound like it is very sensitive. You might look at the fusible link, and check for a bad diode in the alternator. The firewall connectons are critical.

[Al P.]

Re: 67 Ammeter Question

I have a spare battery gauge, and it does the same thing as the one in the dash, So I know my dash gauge is good.

So today disconnected the gauge in the dash and let the 2 wire connector hang free.

I ran 2 new 16 gauge wires to my spare ammeter, grounded it as well since it is out of the car and the gauge does the same thing.

When the car is parked sitting idle, the needle is straight up with almost identical battery voltage of 12.75 on both leads.

When I put the parking lights on (while parked) it reads -20a on the left side of the gauge. When I check the 2 leads voltages of the gauge with the parking lights on there is only a .10 voltage differential between both leads (1/10 of a volt) - So it seems like my battery gauges are super sensitive and show high readings.

When I just open my door and the courtesy lights go on, the gauge deflects to the left ever so slightly.....When I sound the horn the needle deflects left a bit as well. When I put the emergency flashers on it deflects left to 20-30 amps...And again, I have driven the car for the past month with no other issues!

Like I said the ammeter is working properly but showing high readings...I changed everything - even the horn relay to today - No Change.

My next step is to start eliminating some circuits to see if any of them have any effect on this issue. I suspect not, but will test anyway.

Id like to just work on the meter itself to "modify" it to read half of what its reading now and I think Id be good to go......How could I modify the gauge so its not reading so high?

[William C.]

Re: 67 Ammeter Question

I don't believe the gauge has modified itself. I believe you have a high resistance in the sensing circuit causing the voltage drops in the sense wire to be greater than normal. That is why your readings are high in both directions, the voltage drop across the sense wire is greater than normal. When no current flows either ito or out of the battery, the sense wire does not create any voltage drop to move the needle. I'd start with the connections at the firewall and look for corrosion.