Anyone know of a source for a 24 volt ammeter for an HD11? All I can find are one wire digital ones or $150 aircraft gauges.

https://www.grainger.com

Edited by steve(ill) - 19 Feb 2018 at 12:15pm

I think, but am not sure if this is correct, that the ammeter doesn't care what voltage is applied to it.  It just measures the electrons that pass by.

Garlic Pete, thanks for the info. I was curious if that is the case. I can find many that say 12 volts, I’ll try one and let you know. My multimeter is showing around 27+ volts when charging. Both my HD11s have ammeters, not voltage meters. I believe they came that way because my dad bought the tractors new and he said he never replaced them.

The seller, hwaccumulator, said they only work with 12 volt. I put a 35 amp one wire alternator on it, I think it should work.

I agree with Steve. An old mechanical ammeter should work on 6, 12, or 24 volts as long as it's range can cover the charge rate. How many 6 volt tractors and other vehicles have been converted to 12 volts and the same ammeter used by just reversing the leads? They work until the current over loads them, which might be a long time. The likely reason a manufacturer will say an ammeter is for a certain voltage is the lighting kit/bulb they supply with it, as lighting is more commonly supplied in the gauges than it used to be. Stewart Warner gave an option of 12 or 24 volt lighting kits for their ammeters.

jerbob, I may not be following what you are asking but, reversing the wires won't reduce 24 volts to 12. On a 24 volt positive ground system, with two batteries in series, you should have 12 volts at the negative terminal of the battery that has the positive post connected to ground. You can check that with a voltmeter. You would have to run a separate wire from there to supply your light switch with 12 volts. You could put a resistor in the 24 volt supply to the lights and reduce it to 12 volts. It would seem it would be easier to get and install the right 24 volt bulbs and reduce the chances shorting something out. Years ago I remember seeing screws driven into the lead connections between cells on the old 12 volt tar topped batteries so people could run 6 volt accessories from them or resistors installed for the same purpose. I also remember seeing somethings go up in smoke from these taps as well. If you decide to do something like this please put a fuse in your wire near the battery.

Just to clarify. A voltmeter can be hooked across the battery terminals to check draw down when starting. An ammeter should never be connected across the battery terminals, that can get someone hurt. A regular ammeter might be used to check for parasitic draw, in series, between one battery terminal and its cable, but often that needs a meter that reads milliamps. One would need a big ammeter,(400 + amp range), if it is to be hooked in series between the battery terminal and battery cable to check stating draw. A -30 -0- +30 ammeter would be a 30 amp meter, it is for designed for 30 amps either way from zero.

I agree with you and have done the same for radios. It is often done and does work if done correctly.

Jim.ME wrote: jerbob, I may not be following what you are asking but, reversing the wires won't reduce 24 volts to 12. On a 24 volt positive ground system, with two batteries in series, you should have 12 volts at the negative terminal of the battery that has the positive post connected to ground. You can check that with a voltmeter. You would have to run a separate wire from there to supply your light switch with 12 volts. You could put a resistor in the 24 volt supply to the lights and reduce it to 12 volts. It would seem it would be easier to get and install the right 24 volt bulbs and reduce the chances shorting something out. Years ago I remember seeing screws driven into the lead connections between cells on the old 12 volt tar topped batteries so people could run 6 volt accessories from them or resistors installed for the same purpose. I also remember seeing somethings go up in smoke from these taps as well. If you decide to do something like this please put a fuse in your wire near the battery.

The old ACs running 6 volt positive ground. When switching to 12 volt it's negative ground. That's why you reverse polarity on the ammeter.

Thank you for responding Jim.ME

I misspoke and didn't mean to say crossing the wires to go from 24 volt to 12 volt. I was trying to say that if I wanted to cut in a couple of 12 volt lights to the rear of the tractor, do I hook up the wire to the negative post which on my hd16 is the positive. Or the positive post which is going to ground. I have 2 12 volt batteries connected per manual and the positive post goes to ground. In this case, the negative is acting as the positive and my wire and switch goes to that post correct? I believe several have commented on that later in my post.

I thought about it and as I have put in 2 new 24 volt headlights, I can do same for the rear and not fools with using one battery or the other. I can just tie into the line going to the front lights I believe.

Obviously I am not experienced in the wiring on this tractor but learning.

Thank you and everyone for responding.

steve(ill) wrote: we use to put CBs and Radios in crawler tractors that were 24 volts.... you just run a separate wire to ONE battery ( that has the other side grounded to frame) to get 12 volts... Done all the time.

This one line,,, would go to the negative post on a Positive ground system correct?

Perfect Steve. Thank you

um, Steve , you're diagram will blow up the radio PDQ !!!

You've shown the dozer to be +ve ground, so feeding MINUS 12 V to the radio...poof !!
 I haven't seen a +v gnd radio in 4 decades..but if the radio is original to the dozer, and the dozer IS +ve gnd, then it'll work fine but NOT a new,off the shelf radio.

just food for thought.
Jay

The problem with drawing 12 volts off the center like that is that it makes the batteries ‘unbalanced’, and one battery will go dead or you will overcharge one because of it.
Much better to convert the lights to 24 volt.

For a radio, one could use a resistor to drop voltage to the correct level.

Edited by TramwayGuy - 27 Feb 2018 at 5:55am