how does the amp meter function?

[52concord]

i have a 1950 plymouth with 6v positive ground system and a brand new battery. how should the amp meter work? right now when i start the car with no headlights on it stays at 0 at idle and driving. than when i turn head lights on it goes to discharge around 20 at idle, then i rev it up it returns back to 0. does that sound like its working right? i checked voltage at the battery with a fast idle and its showing 6.3 volts, sounds low to me.

[Niel Hoback]

The amp meter is working correctly, showing you that the generator and regulator are functioning correctly. The voltage regulator could be adjusted to raise the output a bit, but since it keeps the battery charged there is no need to tinker with it. Its fine, enjoy it. 

[greg g]

If your system is working with a full charged battery, the regulator should only call for minimal work from the generator.  The system should only try to replace the juice used.  So if your battery is in good shape and fully charged, it should show only a minimal positive charge if your car starts quickly.   Again if the battery is in good shape the recarge rate at 6.3 volts is likely good also.  As far as the healight drawing 20 amps, that seems a bit high.  I might want to go through all the connections you can find in the headlamp harness and check that all the connections are clean and tight.  Also check where each head lamp grounds to the sheet metal of the car body and assure those points are clean and tight.  Finally if your car is not equiped with a body to engine or body to frame ground strap it is a good idea to add one.  

[Plymouthy Adams]

depends on if he is running high beam position on the dimmer....and do not forget that you must also add the wattage of the front and rear parking light and any dash lights that may be switched on and or what selected brightness they may be set.  This will quickly add up                                             

[rallyace]

A 6 volt system with 55 watt headlights should draw about 18 to 19 amps so seeing 20 on the gauge is not bad. Watts divided by volts equals amps so 110 watts (two headlamps at 55 watts) divided by 6 volts equals 18.33 amps.  Add in a little for the running lights and dash lights and you are where you should be.  I agree with Greg, clean all connections and make sure you have good grounds both from the lights to the chassis and from the chassis to the engine block.

[greg g]

I was thinking low beam at 30/35 watts, and added in a couple for associated lights.  The other big source of higher than normal resistance might be the dimmer switchitself, especially if not in constant use to keep the contact points inside burnished.

Edited February 26, 2016 by greg g

[Frank Elder]

[Seaside Pete]

The amp meter is working correctly, showing you that the generator and regulator are functioning correctly. The voltage regulator could be adjusted to raise the output a bit, but since it keeps the battery charged there is no need to tinker with it. Its fine, enjoy it. 

 

How do you adjust the voltage regulator? I didn't know you could do that. What is the advantage of adjusting, does it give a higher charge rate?

 

[Plymouthy Adams]

Seaside Pete, on 26 Feb 2016 - 04:58 AM, said:

How do you adjust the voltage regulator? I didn't know you could do that. What is the advantage of adjusting, does it give a higher charge rate?

 

Pete, do you own the service manual for your car?  If not, I recommend getting one as it is a highly valuable tool for maintaining your vehicle and the systems that support its good health.  The generating section has a good step by step on the function of the regulator and how to go about adjusting it.   Read it through a couple times first to get the operating principle established in your mind first.  Good luck 

[mopar_earl]

What is your idle speed? My car discharges at idle as the generator is cutout. I have a semi auto trans so my idle speed is low. Low enough not to charge at idle. So my car always shows discharge on my amp gauge at idle.

Amp meters have been known to cause dash fires. I plan to disconnect/bypass mine and add some fuses at some point.

Earl

[Plymouthy Adams]

lot of folks will upgrade a car equipped with an ammeter from an original generator powered system to use an alternator and not upgrade the rating of the meter to work within the higher charging rates the alternator provides...also they do not inspect the old harness for common breakdown due to age, loose connection will also come into play with the higher current that is the alternator charging system.  These problems can usually be avoided if one just thinks a bit before moving forward with their upgrades/changes to a system.  Most alternators do not use the early style amp meters also as they typically use a shunted variety that instead will sample current flow charge/discharge and not so much the accurate reporting of said current flow in amps.  Common today is a volt meter for monitoring the alternator output.

Edited February 26, 2016 by Plymouthy Adams

[46Ply]

Regarding ammeter reading, I have a lot of bounce and erratic movement in the needle on the gauge.  I think it is reading correctly, because I can see it fluctuate in rhythm with the turn signals, and also increases when necessary, (after excessive use of the starter when I had the spark plug wires off, and couldn't figure out why it wouldn't start).  SEE my post on Stupid is and Stupid does!!

 

Would this be a faulty gauge or coming from the regulator? 

[greg g]

If you can get the cover off the regulator you might consider cleaning up the contact points inside.  It is important to use a points file not sandpaper or emery cloth for this so if you don't have  points file don't do it.  The abrasive material can become imbedded in the contact material making it worse instead of better.  One the outside i would clean up all the contacts related to the regulator generator circuit.  Also if you do not have a body to frame/engine ground strap add one.  You can easily make one using a couple strands of length of 10 gauge wire paired together from a point of the firewall to one of the starter bolts or even one of the bolts holding the oil filter bracket to the block.

[Niel Hoback]

I strongly believe that you are trying to fix something that isn't broken. You can tinker all you want, but it probably won't work any better than it is now.

[52concord]

So everything was working good then i took the plymouth out yesterday and its overcharging. The amp meter is acting like a tachometer every time i rev. At idle it stays at 0 but when i rev it up it goes up to +40 with headlights off. With the headlights on at idle it goes to -20 and when i rev it goes to 0 and doesnt go past that. It also has a new voltage regulator. Any idea what it could be? im thinking maybe its the generator.

[DonaldSmith]

The voltage regulator is not regulating.

 

Or else the battery is really run down and needs a healthy charge.

Edited March 9, 2016 by DonaldSmith

[Niel Hoback]

Put the old regulator back on.

[Plymouthy Adams]

check also for tight wire connections and especially a good clean ground connection ..

[52concord]

so the overcharging was caused by the generator, i got it rebuilt and went back to normal. One thing that i think isnt right is the volts its putting out, car turned off the battery is at 6.3v, when car is at idle its at 6.3v, once i rev it up to around 2000rpm it stays the same, shouldnt it jump up to 7-8v while revved up?

[Niel Hoback]

Not if the battery is fully charged and there isn't any need for more electric power.