Ammeter “Normal” Temperature?

KMBeers

KMBeers

Senior Member
Ammeter “Normal” Temperature?

I have a 6V Positive ground standard electrical system, generator, cutout, and new battery, where I can see 3-4 Amps on the ammeter and 8.2 volts at 1800 rpm on the engine. Does anyone on the Barn know how hot the Ammeter gets under these conditions? Everything is working as expected it is more a matter of curiosity. This is a repop Ammeter where I soldered the internal terminals and painted the back face black.
 
Re: Ammeter “Normal” Temperature?

Heat is caused by current through the shunt bar. Repop is anyone's guess. Your observations are good for city driving. For higher long term speeds, I would set the third brush back a bit.
 
Re: Ammeter “Normal” Temperature?

W=I^2 X R . For an ammeter in good working condition the resistance is very low. Assume it is 0.01 ohm. For a current of 4 amps the Watts would be 4 X 4 X 0.01 = 0.16 Watts, which is very low. The temperature would then depend on the how efficiently that power is dissipated. The heat is probably carried away by the wires, which are copper and good heat conductors. So the temperature rise is going to be on the order of half a degree F or less. If you have an IR temperature gauge you can try to measure it.
 
Re: Ammeter “Normal” Temperature?

If the two screws that hold the wires to the shunt are loose it will cause a resistance, and the amp will get hot.
Tom Endy
 
Re: Ammeter “Normal” Temperature?

Ok, thanks everyone for the input. I have the points where the studs attach to the bar soldered which should keep them in good contact and the resistance down. Nkaminar, I will try and measure the resistance. I don’t have an ohm meter I trust in that range so I will try the one at the office we use to measure bonding resistance on some aircraft parts we make. It will be interesting to see what the values are. Badpuppy, before I get her out on the road again I will look to resetting the third brush to see if I can get the voltage lower, which will also lower the current. Using LED lights now, I will try and keep the battery from discharging while driving at night, (which I don’t do very often) but not high enough to cook the water out of the battery. The saga of using the generator…..
 
Re: Ammeter “Normal” Temperature?

The saga of using the generator…..
Click to expand...
There are aftermarket Voltage Regulators for use with the Model A Generator. These are based in the "cutout" body IIRC.

Check out the thread https://www.fordbarn.com/forum/showthread.php?t=336661&highlight=voltage+regulator

One member here, now deceased, used to make a VR that was "In" the generator body. You used the cut-out in its usual form and manner.

https://www.fordbarn.com/forum/showthread.php?t=310317&highlight=Wesenberg+Tom+passing

VRs keep you from "overcharging" your battery and "boiling off" the electrolyte.

Joe K
 
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Re: Ammeter “Normal” Temperature?

The new voltage regulators that mount in the generator body are the cat's meow. I highly recommend using one.
 
Re: Ammeter “Normal” Temperature?

Flathead said:
The ammeter should not get hot.
Click to expand...

my thots, too! heat is also caused by loose connections. i had a voltmeter that ran warm, very warm on another vehicle. gauge panel made by custom tinbender for me. i stopped in one day to chat and mentioned. he said heat can be caused by loose connections. sure enuff, i had loose nuts on terminals. with batt, disc. i tightened. ran cool to touch from then on...
 
Re: Ammeter “Normal” Temperature?

I looked through the link provided by Joe K and also the modeltstarters.com website. They are showing out of stock for the regulator. It looked like from the older post they were still having issues as late as November 2024 so I reached out to them to see when they might be available. I like the idea of using a regulator. Will keep the battery from boiling itself low.
 
Re: Ammeter “Normal” Temperature?

Jeff had problems with the positive ground version but is working on it. Mike Hill sells an internal type that has good reviews. He's in Calgary, Alberta.
 
Re: Ammeter “Normal” Temperature?

Badpuppy, you are correct. I got an email back from Jeff at modeltstarters.com and they are still designing the 6V positive ground version. I am on “the list” though….
 
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