Electrical: Ammeter Reading

[Commander Eddie]

I searched all the threads here relating to this subject and could not find the answer to this question, so I will post it for some advice.
I check my gauges as I drive pretty regularly. (I also drive a school bus now and then and that is part of our training). I do not remember my ammeter showing any significant discharge at idle when I had things turned on such as lights, fan, or windshield wipers. On Tuesday of this week I had to replace a completely dead battery. I mean this poor things was profoundly dead. I replaced it with the correct battery and the truck fired right up. I drove the truck to work the next day. It was dark and raining so I had all three of the items listed above turned on. I watched the ammeter closely and noted that at stop lights when the engine was at idle the ammeter showed a discharge of about 25+ amps. When I revved the engine the needle shot back to a positive charge of nearly the same but settled back down fairly quickly to about 3-5 amps (estimate). I do not remember that much of a discharge at idle before. When I turned everything off but the engine the ammeter showed a discharge of about 5 amps, which seems reasonable. The truck still has a generator, not an alternator.
It may be that this is perfectly normal and I need not be concerned, but I thought I should throw this out here and see what you guys think.

[Skip Lackie]

Six volt or 12 volt system?

[Commander Eddie]

Six volt or 12 volt system?

Skip, the truck is a '61 Champ with a 12 volt negative ground electrical system.

[Skip Lackie]

I don't think -25 amps at idle sounds all that bad. The owners manual will give you the fuse ratings of each system, which will be a few amps more than their maximum expected draw. Seat of the pants estimates for actual draw: headlights: 15-18, heater fan: 5-7, wiper motor: 5. Plus the tail lamps on some vehicles (I don't have a Champ) are on a separate fuse and draw another amp or so. At idle, an OEM generator is producing something close to zero. So as long as the ammeter shows +3 or 4 amps a few seconds after you rev up the engine, I think you're okay. That said, it might be worth checking various connections for corrosion, which can increase current draw. For example, pull the connectors off the back of the headlights, and check the various fuses. Next time you're under the dash, disconnect the wires from the light and wiper switches and see if the connections are clean and shiny.

[TWChamp]

Do you have stock headlamp bulbs?
What is the idle speed?

That sounds like a lot of drain for a 12 volt system at idle. My 6 volt system will idle at 0 with nothing turned on, and will be between 0 and -10 with the lights on at idle.
Before replacing a battery, I always put it on my 6 amp charger for 24 hours, then see if it holds the charge and cranks as it should. The battery in my 1950 Champion will be 13 years old this next April, so I will replace it due to age, plus I can tell it's not as good as it used to be.
Besides, 13 is an unlucky number, and I don't want to get stranded! LOL

[Commander Eddie]

TWChamp - The truck has stock incandescent headlight bulbs. Idle speed is around 500 RMP. I don't have a tach so that is just a guess.

Skip - I'll keep an eye on things and check connections as I have time. I made sure to clean the battery cable connections when I replaced the battery.

[rstrasser]

Commander Eddie;
To me the idle current sounds high.. An ammeter; if it is connected correctly displays all the current going into and out of the battery. In order to show 5 amps at idle the generator would have to be putting out nothing.
Now the question is what is using 5 amps of current with only the engine running and all accessories turned off. It does not take 5 amps to power an ignition system.
If there is also something like a electric fuel pump; then that might explain the 5 amps and everything is OK.
Find out what is using the extra 5 amps and then the plus and minus 25 amps becomes 20 amps and seems normal to me.
Ron

[thunderations]

Just a thought, but after replacing the dead battery, did you polarize the voltage regulator?

[Commander Eddie]

Just a thought, but after replacing the dead battery, did you polarize the voltage regulator?

I did not. How is that done?

[Bill A]

If the truck still has a generator then the charging output will be on the low side at idle, heck it isn't all that much when running and that is the primary reason so many install alternators. My dually has maybe an 80a alternator and it will discharge when it's raining on a cold night with everything running at idle.

[rstrasser]

Commander Eddie;
No need to polarize the generator if the ammeter goes to the plus side when the engine speed is increased. If a generator is not polarized it will not put out any current.
Ron

[Commander Eddie]

Commander Eddie;
No need to polarize the generator if the ammeter goes to the plus side when the engine speed is increased. If a generator is not polarized it will not put out any current.
Ron

Understood. That is what I was thinking and why I checked to make sure it was charging after I replaced the battery.
If I were to summarize what I have learned thus far I would say the system is probably fine and I should not be overly concerned. If my assumption is incorrect, please let me know.

[StudeRich]

If the Generator is showing a charge as I think you said, it does not not to be Polarized.

The other thing is I would seriously wonder if the Aftermarket Ammeter is correctly installed.
I am about to install one in my "New" Champ, so I know it won't be very easy to do it right, and some people would take the easy way out.

I will need to make a New 10 Ga. wire extension from the Lug on the Power feed from the Solenoid that went to the Ignition Switch and reroute it to the input of the Ammeter because to won't reach.
Then make another new wire to Power up the Ignition Switch from the "Output" side of the Ammeter to the Ignition Switch.
In other words, if all of the current flow from the Voltage Reg. and Battery is not going INTO the Ammeter, and all of the Load going OUT connected on the other side of the Ammeter, you will not get the readings you should like a Factory wired Hawk would with a Factory Ammeter.

Then, you always know the condition of your Charging system instantly.

Anyone can easily connect a Voltmeter to ANY Hot wire and read the Voltage, but when your Generator, Alternator or Voltage Regulator fails you will not know that you are slowly starting to lose Voltage, and will probably never notice until the Engine will no longer turn over.

[thunderations]

Use a jumper wire from the Armature terminal on the regulator and strike a spark to the Battery terminal. if you need more info, Google: Polarizing a voltage regulator. All kinds of info on the internet. Even tells you why you need to do it and when. Says ANY time you replace a battery.

[Commander Eddie]

If the Generator is showing a charge as I think you said, it does not not to be Polarized.

The other thing is I would seriously wonder if the Aftermarket Ammeter is correctly installed.
I am about to install one in my "New" Champ, so I know it won't be very easy to do it right, and some people would take the easy way out.

I will need to make a New 10 Ga. wire extension from the Lug on the Power feed from the Solenoid that went to the Ignition Switch and reroute it to the input of the Ammeter because to won't reach.
Then make another new wire to Power up the Ignition Switch from the "Output" side of the Ammeter to the Ignition Switch.
In other words, if all of the current flow from the Voltage Reg. and Battery is not going INTO the Ammeter, and all of the Load going OUT connected on the other side of the Ammeter, you will not get the readings you should like a Factory wired Hawk would with a Factory Ammeter.

Then, you always know the condition of your Charging system instantly.

Anyone can easily connect a Voltmeter to ANY Hot wire and read the Voltage, but when your Generator, Alternator or Voltage Regulator fails you will not know that you are slowly starting to lose Voltage, and will probably never notice until the Engine will no longer turn over.

Rich,
the ammeter in my truck is the same one that was in it when I purchased the truck a few years ago. It is a Stewart-Warnter gauge, and has been working fine. I am pretty sure it is correctly installed. I will double check all the connections as stated earlier.