Is an ammeter have to have the voltage numbers written on it, or does one with "D" and "C" on it also count as an ammeter?? (Also, what does "D" and "C" stand for?

 

An ammeter registers the number of amps being used by the electrical system. It can have numbers ranging from - to plus and can be anything from 15 to 80. i.e. -15 to + 15 or - 80 to +80. When you start a vehicle you will see the needle go to the + side showing the altenator is sending a charge back to the battery. If you are not running lights, high output stereo or other high draw items, the needle should remain in the middle. If it sits to the left or discharge side, your system is not putting out enough juice to power everything and keep the battery charged. Which will lead to a dead battery. A gauge with D - C is an ammeter, which simply shows a charge or discharge condition.
A volt meter however will have numbers usually up to 18, although some are just colored lines(for people who can't read), a volt meter will only show that your system is putting out the correct number of volts, to many (above 15) can lead to overcharging your battery, bad news. Under 13.5 can lead to a weak or dead battery. Also a volt meter is a quick way to see the charge on your battery, click on the key and look at the numbers.
Me, I prefer an ammeter as your system can be putting out the right number of volts but insufficent amps and you can still end up with a weak or dead battery at a bad time.
Worked with SDDOT where we had an IHC dump truck which pulled 90 amps on a 70 amp altenator. As long as it ran you were good, but let it idle for awhile with all the draw, shut it off and guess what? Dead battery.

 

Thanks for the help. I have a D/C one. Seems to always stay dead center, so I don't know if it's working or not. My battery is not charging and I have now replaced every single thing in the charging system with the exception of the alternator wiring. Wondering if something is wired wrong then. I have no wire from my stator post on the alternator.

 

I have a different opinion as I prefer a volt meter. If the volts are in the normal range, which is about 13-15, then it doesn't matter what the amps are doing. If you don't have the amperage to maintain the demand on the system the volts will be low. A good rule of thumb is to have all the accessories on and the car in drive, and you should see about 1 volt more than you see with just the key on without the engine running. If you see a reading above 15 for any period of time you will start loosing battery acid due to vaporization and over 16 or so will ruin a battery.

 

I prefer the voltmeter approach as well. Usually a battery will sit at 12.4-12.6 volts, so if you're voltmeter is showing 13-15 then you're getting a charge. An ammeter, shows either a (C)harge or a (D)ischarge, but doesn't give you any indication of the state of your battery.

The solution however is simple, pick up a voltmeter and have both.

 

I installed a voltmeter because after owning several 70s Ford pickups, I am pretty sure the amp meter isn't actually connected to anything since the needle never moves.

 

When I put my F-405 guage panel in, the ammeter actually worked. Surprised the heck out of me.

 

I hope to get the F-600 cluster in my 68 this week. I am not quite sure what an F-405 is though. Typo?

 

Thanks for the help. I have a D/C one. Seems to always stay dead center, so I don't know if it's working or not. My battery is not charging and I have now replaced every single thing in the charging system with the exception of the alternator wiring. Wondering if something is wired wrong then. I have no wire from my stator post on the alternator.

Sometimes, if your ammeter is not working, or if you have a charge indicator light that has burnt out, your alternator will not recieve an "excite" signal and will not charge your battery.

 

Yeah, 405 was a typo. The stator connection is not used unless you have an idiot light. It does make a good place to hook up an electric choke. The voltage is 1/2 of the alternator voltage.

 

I have mychoke hooked there but I never realized it was for the idiot light only. I learn new stuff on here all the time.