|
Ammeters for 12v conversions After reading several posts lately regarding 12 volt conversions, 30 amp ammeters and the junk that is currently only available from the dealers, I remembered an old post and found it in my tractor file :D Try this location ;
http://www.tractorpartsinc.com/ford_...es_187_ctg.htm They offer 2 styles of 30 a amp gauge for old Ford tractors and also a 60amp version for any of the high out put alternators. Hope this helps some others out - it did for me. |
Re: Ammeters for 12v conversions I solve the problem by running a jumper wire between the two terminals on the ammeter so only part of the current goes through the meter. The meter is no longer accurate but it tells you what is happening and that is enough.
Charlie Stephens |
Re: Ammeters for 12v conversions The biggest waste of money is the big "sell" to make you think you need a larger ammeter with an alternator. The ammeter in an A only shows BATTERY charge/discharge. It is NOT wired to show total generator or alternator output.
Even if you had a 200 amp alternator and a light bar with ten halogens on the roof, if your battery is fully charged the ammeter will say ZERO even though the alternator is putting out 200 amps. You cannot damage a stock A ammeter even if you run thirty amps through it. The internal shunts on the stock 20A and the 30A meters are identical, only the calibration is different. Driving the meter 50% or 100% over-scale will not hurt a stock ammeter. If it were a high precision wound armature meter, like a D'Arsonval or Taut-Band design, over-scale could damage it. But it is not. It is inductive. It works like a speedometer. Henry's cheap design (used by almost all automotive ammeters to this day) uses magnetic flux from the shunt to deflect a non-electrically connected aluminum pointer within a permanent magnet ring. The stock A wiring will, however, start smoking (think Lucas :eek:) if you run 30 amps through it for more than 10 minutes. Having a dead flat battery will draw ~25-30 Amps from an alternator for about 10 minutes then it will taper to less than 20, finally to zero when the battery is 100% charged. Generator or alternator, any output rating, there is no difference if you use a 20 or 30 amp meter. The disadvantage to the 30 is it is difficult to "see" a 2 or 3 amp discharge as the needle is less sensitive. |
Re: Ammeters for 12v conversions The tractor ammeter is way to big (2") for the Model A instrument panel.
Bob |
Re: Ammeters for 12v conversions MikeK,
Interesting comments. I agree that their is no need for a 30 or 60 amp ammeter. I also feel their is no reason for a 60 amp alternator on a Model A Ford. But, I don't understand your comment about that the ammeter not showing generator or alternator output. If you battery is charged, then an alternator will not have any output, as the regulator stops it,since the battery does not need it. SO the ammeter will show zero. If you have a generator and it is set at 10 amps, the generator will always put out 10 amps, and the ammeter will show 10 amps, because their is no regulator. It shows 10 amps regardless of the amount of charge in the battery. Please help me understand what you are saying, as I dont think you are right.....but unlike many others on this site, I am open minded and always want to learn more. |
Re: Ammeters for 12v conversions I agree with Mike K on this one. Dave Wilton told me basicly the same thing when I purchased one of his 60 amp alternators back in the mid ninties. Unless the battery is very weak you won't see that much charge on the ammeter and then for only a short time. I chose a 60 amp alternator because I wanted to run the 55-60 w quartz halogen bulbs that need a higher output alternator. I run a standard 20 amp ammeter and the 60 amp alternator is still working after nearly 20 years and the halogens are as bright as modern car headlamps.. I use a 20 amp ammeter on my 12 volt converted roadster with an original generator and a Fun Projects regulator. The needle on the 30 amp ammeters doesn't have to move as far to indicate a small amount of charge. Mid point on a 20 amp ammeter is 10 amps, mid point on a 30 amp ammeter is 15 amps. A 2 or 3 amp charge is hardly detectable on a 30 amp ammeter . Just my take on the matter .
|
Re: Ammeters for 12v conversions Quote:
http://i233.photobucket.com/albums/e...aysAmmeter.jpg |
Re: Ammeters for 12v conversions SteveB31,
Another way to look at it...For a normally wired Model A, the Amp meter shows the amount of current going into (+) or out of (-) the battery. The amp meter does not show the total amount out of the generator, it just shows the "extra" amount that goes to the battery after the generator has provided power for the ignition and if on, the lights and horn. Marc |
Re: Ammeters for 12v conversions I understand exactly what you mean. The way it was stated in your first post was unclear, but I get what you are saying. I had never thought of it that way before. thanks
|
Re: Ammeters for 12v conversions Gosh - I wish I had enough brains to absorb all the knowledge that is to be found on the FORD BARN FORUM ! Being a non-mechanical guy and quite a bit of a 'dunce' about even the basic mechanical workings of the Ford Model A, I appreciate such useful (to me) tools as the scematic diagram that Mike K has posted above.
Thanks so much guys ! Doug Vieyra, Eureka, Calif |
| All times are GMT -5. The time now is 09:22 PM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2025, vBulletin Solutions Inc.