Ammeter issue

Ordsgt

Ordsgt

Senior Member
I got my car back together (1930 Tudor) and it runs and looks good. I am running a Nu Rex 6v alternator. It was charging fine on the meter and everything appeared good. Driving down the road the other day the ammeter went to 0 and stayed there. I went home and put a voltmeter on the alternator and it showed 8.2 volts but nothing on the amp meter. I drove it later that day and it showed 12 amp charge but after a few miles it went back to 0 and stayed there. I replaced the meter but it still shows no charge but voltage indicates it is charging. I have checked the harness connections and all appear good. Wiring harness is a couple of years old but in excellent condition. Had no issue before the car was completely torn down and rebuilt from the frame up. Any ideas ?
 
Sounds about normal to me. Once the battery is charged, the internal regulator doesn't charge any more than needed to keep all of your accessories happy. :)

My amp gauge always shows a charge at first startup, then settles down. This is probably due high draw from the starter.
 
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This is the characteristic of having an internal electronic control unit to the alternator. The only thing I get concerned about is that in the case of the 6-volt conversion alternators, the electronic voltage/current controllers usually allow for a higher than normal voltage output so they tend to overcharge the battery during long daylight drives. At night, it's no problem since the lights are helping to consume the excess to a certain degree. A person can run with the lights on if they choose to.

The old 3-brush units with the aftermarket voltage regulators, like the Fun Projects type installation, were about as good as it gets for a 6-volt battery but they give about the same indication on the ammeter as an alternator does.
 
Alternator sounds like it’s doing its job, second drive charging at 12 amp sounds like you have a draw. Did you leave the headlights on, honk the horn a lot, brake light switch sticking on ?
 
Well a second issue came out. Started the car up and there was no lighting no horn. After running RPM up got power to that circuit. Just surprised as none of this was happening before the tear down
 
Is the ground cable connection good? Clean, and tight.
At the battery, and at the frame,
Secondary ground strap to the motor?
 
Ordsgt said:
Well a second issue came out. Started the car up and there was no lighting no horn. After running RPM up got power to that circuit. Just surprised as none of this was happening before the tear down
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Are you new to alternators? Was the alternator "excited" (show a charge on the ammeter?) at this point? Some alternators need to be at a higher RPM to start charging when first started up.

My PowerGen starts charging at startup.
 
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Add a volt meter. You can buy an addition to your instrument panel that hangs below. The volt meter is a better tool for keeping track of your alternator and battery. Before you start the car, turn on the ignition and look at the volt meter. It should register about 6.3 volts for a healthy battery. After you start the car the battery voltage should start to come up (with a fast idle or driving down the road). It should eventually reach about 7 volts or a little more. 8 volts is too high and may be caused by a bad ground. As the battery voltage comes up the current shown on the ammeter will go to zero. Even with the lights on it will read zero because the alternator is supplying current to run the lights and not the battery.

Regarding no power to the lights and horn before the alternator starts to come on: That sounds like an electrical issue. It could be a bad ground or a bad connection somewhere. It is probably related to the high voltage (8.2 volts) you measured at the alternator.
 
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nkaminar said:
Regarding no power to the lights and horn before the alternator starts to come on: That sounds like an electrical issue. It could be a bad ground or a bad connection somewhere. It is probably related to the high voltage (8.2 volts) you measured at the alternator.
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100% this. Something between the alternator and battery is not making good connection. That is the electrical loop that goes from the starter switch to the terminal box to the ammeter, through the ammeter, then from the other side of the ammeter back to the terminal box and to the alternator.
 
Thanks for all you input, Problem solved! Traced out the wires and checked connections found battery to starter loose and output from starter fuse assy also loose. Now had power to the fuse but nothing coming out. Pulled fuse and it looked good but put a meter on it anyway and it was no good. Replaced the fuse and now had current to horn lights etc. So I went to start it up and it would not fire. It has always fired right up. looking under the hood for a problem and noticed coil wire was not in. Had disconnected it to check in the junction box. Connected wire and engine fired right up and ammeter went to 12 amp.
Happy Model A man
 
Ordsgt said:
Thanks for all you input, Problem solved! Traced out the wires and checked connections found battery to starter loose and output from starter fuse assy also loose. Now had power to the fuse but nothing coming out. Pulled fuse and it looked good but put a meter on it anyway and it was no good. Replaced the fuse and now had current to horn lights etc. So I went to start it up and it would not fire. It has always fired right up. looking under the hood for a problem and noticed coil wire was not in. Had disconnected it to check in the junction box. Connected wire and engine fired right up and ammeter went to 12 amp.
Happy Model A man
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Strange, how did the engine run with the fuse blown. With fuse blown you would have no battery power to the junction box?? Unless it is not wired correctly. :confused: :confused:
 
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I have electronic FSI ignition which is directly off the battery terminal. That is what FSI states to do in the instructions
 
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