Stupid question: ammeter

[June J]

Simply put it boils down to the fact that the armature in a generator has wire windings and as such cannot be spun at high RPM's as an alternator (the alternator has a rotor not an armature). Therefore at idle speed the voltage cut out will open as the generator voltage will fall below the battery voltage (the cut out prevents the battery from turning the generator into an electric motor and burning it out!!).

Its entirely possible that your ammeter may show a slight discharge (minus) at idle when you have full lights on. As the engine speed increases so does the out put of the generator in both voltage and amperage, thus you will see your ammeter show a positive reading, but only until the battery is fully charged, at which point your ammeter should show only a very slight plus reading. This is all because the voltage and current regulators will effectively control the generator output to match battery charge level and load.

Your volt meter should read around 14.5 volts with the engine running at anything above idle speed. You can actually leave your volt meter on for long periods, just remember to switch it off when you turn the engine off or it will drain your battery over time. I have had my WC 57 for 10 years now, the volt meter is wired via a relay so its on as soon as the ignition is on, and I have never burned out the meter.

Cheers

Ian

[Lang]

I have had a couple of Carryalls. The first was original generator but I can't recall the charge indications. My current Carryall has an alternator so no contest.

I don't think the size of the generator has any bearing on the speed at which it begins to operate but if, as you say they have a smaller pulley it would equate to a higher speed in a standard vehicle. I can see where that would be a good design feature in a radio equipped vehicle to prevent you having to run the engine at unnecessarily high revs during parked operations.

I have my Carryall generator and a standard WC51 generator on the shelf - will compare pulley sizes.

This is an outstanding explanation of generators.
http://www.venselenterprises.com/techti ... rators.pdf

Lang

[Kaegi]

I also used to run a late 50s 12 volt 55 amp that was small like most vehicles in the late 50s and it never discharged at idle under load either.
that one came from a Chrysler industrial powered forklift. was never available in cars. autolite stuff for me always performed better than my GM 12 volt generator vehicles I have owned.

I would n't switch to an alternator on a stock 12 volt WC they wont hold up in harsh conditions and you cant compression start the truck with no battery like you can with a gen.
there are very HD alternators available but the average automotive units are kind of wimpy when it comes to failure if a wire shorts momentarily, high heat, water etc. no diodes to fry in a generator.
but we run what makes us sleep at night I suppose. to each his own.