24 volt ammeter

Correct Everyone.

I jumped in on the original post to ask a question regarding adding 12 volt lights to my 24volt 16. At the time I had a couple of nice 12volt lights and thought I would use them. I never brought up the radio think, but for giggles, I do use radio ear muffs for protection and even with them on, hard to hear any music when my 16 is barking. Wanted to thank all the ides and suggestions as it gave me insight as to future work in the wiring department.

I would agree , changing to a NEGATIVE ground makes things easier to add new equipment......... on the other hand, I don't think he ever mentioned adding a radio.. That was just part of the conversation.. POSITIVE ground is fine for the old tractor with new lights......... If your adding an alternator,  radio or "other" it might be best to convert to negative ground at that time to avoid problems.

Thank you Jim. Handy and now in my archive of tables and saved data.

DaveKamp wrote: A RESISTOR will not make a 12v radio work on 24 volts. To make a 12v radio work on 24 volts requires either a DC-DC converter of sufficient current rating, or just tap across the first battery. Imbalance across the batteries in this application is not a substantial concern- the load, in comparison to the batteries' capacity, is very small. If it's the cab-heater blower fan, that's a different story. As for ammeter, there's no 'voltage' associated with the ammeter's design, only for the illumination of the gauge. If it has a 12v incandescent lamp, just buy a 24v incandescent lamp to fit the same socket (typically they plug into the back), and call it good. Or use an LED that's rated for 9-36v. As for floodlamps, if you're not needing 'authenticity', then look into LED floodlighting. All the units I've been putting on my machines will operate fine over a very wide range... most are rated to over 28v, and will light up on a 9v battery too...

Good thoughts Dave and thank you. I will admit that I hadn't thought of replacing the 12v light bulb with a 24volt one. That would be great for the added illumination.

Jim.ME wrote: I believe you said earlier you already have 24 volt headlights. I would use the same source your current head lights use. Such as if the headlights use a wire coming from the ammeter to the headlight switch, install a new wire from the same terminal on the ammeter to your new switch, which could be mounted near the current head light switch, then run a wire from the switch to your new rear lights. Or you might be able to run a jumper from the power terminal of your current head light switch to your new rear light switch. Install a fuse somewhere in the circuit, near the power source is best. This is personal preference: I would keep the switches near each other; not run an odd power wire to a switch mounted remotely, like by the rear lights, less chance of it getting left on. Some equipment ties the rear lights with the head lights to the same switch, all on at once. Another option: you might change your current switch to a multi position switch, like a universal head light switch. Connect the head lights to the tail light terminal and the rear lights to the head light terminal. Pull to first step for head lights, pull to the second step and you have both head and rear lights.

Based on what you are saying, I think it makes most sense to just tie into current headlights so when one is on all are on. Thank you.

A RESISTOR will not make a 12v radio work on 24 volts. To make a 12v radio work on 24 volts requires either a DC-DC converter of sufficient current rating, or just tap across the first battery.

Imbalance across the batteries in this application is not a substantial concern- the load, in comparison to the batteries' capacity, is very small. If it's the cab-heater blower fan, that's a different story.

As for ammeter, there's no 'voltage' associated with the ammeter's design, only for the illumination of the gauge. If it has a 12v incandescent lamp, just buy a 24v incandescent lamp to fit the same socket (typically they plug into the back), and call it good. Or use an LED that's rated for 9-36v.

As for floodlamps, if you're not needing 'authenticity', then look into LED floodlighting. All the units I've been putting on my machines will operate fine over a very wide range... most are rated to over 28v, and will light up on a 9v battery too...

I believe you said earlier you already have 24 volt headlights. I would use the same source your current head lights use. Such as if the headlights use a wire coming from the ammeter to the headlight switch, install a new wire from the same terminal on the ammeter to your new switch, which could be mounted near the current head light switch, then run a wire from the switch to your new rear lights. Or you might be able to run a jumper from the power terminal of your current head light switch to your new rear light switch. Install a fuse somewhere in the circuit, near the power source is best. This is personal preference: I would keep the switches near each other; not run an odd power wire to a switch mounted remotely, like by the rear lights, less chance of it getting left on. Some equipment ties the rear lights with the head lights to the same switch, all on at once. Another option: you might change your current switch to a multi position switch, like a universal head light switch. Connect the head lights to the tail light terminal and the rear lights to the head light terminal. Pull to first step for head lights, pull to the second step and you have both head and rear lights.

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

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

Perfect Steve. Thank you

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?

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.

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.

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

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.