VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Ammeter Accuracy

Having lots of fun driving around town in our' 37 Master Coupe. I have put about 120 miles on it with only a few minor issues.

What are your observations with respect to in-dash ammeter accuracy? Here is the situation I have.

Based on information in some prior posts and the '37 Engineering Specs I wanted to confirm that the generator was providing the right output. When I rebuilt the generator I set the 3rd brush at 2 commutator bars from the main brush.

I was concerned because the dash ammeter was showing 15-16 amps with no lights and over 20 amps with the head light switch in the second position (no resistor). With the lights on it does show a slight plus charge. This car does have a sealed beam 6v headlights and I have put the higher candle power bulbs in the brake and tail lights.

I connected an ammeter directly to the battery side of the cutout on the generator. I was getting about 14 amps with the lights off and about 19 with them on. Remember that the ammeter has already subtracted the ignition and fuel gauge load (about 2-3 amps).

Based on that difference I connected a different ammeter and got readings within 1 amp of the first one. I am also getting about 7.9 volts which I feel is very acceptable.

Should I be concerned with the what seem to be high reading from the in-dash ammeter? Am i getting too much from the generator and running the risk of overheating it?

Thanks for the help.

I would say you have it adjusted as perfect as possible with out better equipment. The generator is designed to put out up to 21 amps or so . Being that the generator is air cooled it can safely put out 21 amps. That how I set the generator on my 1934 using the later air cooled generator with the pulley fan. Never had a problem. While I did not have sealed beams had higher C.P. head and tail light bulbs (dual) and would just be a bit on the + side unless you went over 50 MPH. The 3 brush generator peaks arounr 50 MPH and the charging rate drops after that.

I dont think you have a problem, most automotive instruments are not always spot on accurate. Your readings are very close and within specifications.
Tony

Hi Gene and Tony,

Thanks for the confirmation that my readings are in range.

One interesting point and the reason I had to question the ammeter + readings is that the discharger readings seem much more accurate. Those readings all match the calculated loads within about 1 amp.

Gene: Just got my confirmation for the Middle West Meet. It is a shorter time there than I would like but I will be there mid-Wednesday afternoon. See you there!