Ammeter to Voltmeter Conversion

[theguruat12]

If your interested when i get out of the oilfield and get home i can show you how to make it work with the 3g swap, mine goes almost to the full discharge side then slowly comes back as the glow plugs warm up, then shoots back over to the charge side when started, slowly coming back to little charge as the batteries recover, just like it should.

Did you just install a new shunt?

I'm very interested. I'd love to have both. If my ammeter worked I'd leave the old one in there and put a voltmeter on my a-pillar.

 

[oregon96psd]

A shunt isn't something you can take out and hold in your hand, its a way of measuring current. All the factory ammeter does is take a small amount of the charging current and run it through the meter. All you have to do is take the wires that run from the gauge and put one to where the alternator charges to, and one where the load pulls from. I should be around my pickup after the 8th, I can take pictures then.

 

[theguruat12]

A shunt most definitely is something you can hold in your hand. The ammeter takes a proportional amount of current going through the main wire because its in parallel with the primary wire (the shunt). The resistance of the shunt has to be a specific value in relation to the internal resistance of the ammeter itself. That's how it determines the proper proportion of main current to the signal current.

I'm interested in how yours operates though, I've not seen one function with a 3G. Could you post a video of yours when you start the truck? I'd like to see what kind of values you see when it's pulling heavy current and charging.


Sent from my cyborg implant

 

[oregon96psd]

so where is the shunt in the factory setup? I can get a video of it when i get back, glow plugs pull it almost to the end of the guage on discharge slowly creeping back to about the quarter line, then when started it runs up to about the quarter notch slowly running back to almost neutral. Running down the road with lights and heater running its usually about a needle width toward charge.

 

[theguruat12]

There is a wire in the loom that goes from the alternator to (IIRC) the yellow main supply wire to the cab. The ammeter taps either end of this. The wire itself is the shunt. All a shunt has to be is some kind of resistor, be that a resistor, an actual specifically designed ammeter shunt, or just a wire that has the proper internal resistance. Then, whenever current goes through it, the voltage drop across it is proportional to the current in it (Ohms Law for Resistors). The ammeter in our trucks is actually just a specially calibrated voltmeter that reads said voltage drop.

 

[oregon96psd]

This has got me curious now cause I don't remember exactly what wires go to the ammeter, I know theres two down by the alternator and all I did was move where they hooked up, one I think is on the start solenoid where the charge wire from the alternator goes, and I cant remember where I hooked the other one up. Mine might be setup different from yours because I converted it to a 7.3 glowplug controller and harness. To bad the damn thing is 1,100 miles away lol.