basic Ammeter question

[moody]

Bought an ammeter. Instructions say to install it inline with the horn relay. How can this work? If it is to measure current flow out of the alternator would you not put it inline with the altweernator charging line? What is special about the horn relay?

Sorry to waste your time with the simple stuff but .. no one else to ask.

[dieselcrawler]

An ammeter is useful.. so long as you know what it's telling you. Most have a center "0" point, and show you discharge and charge rates on each side. I don't recall what the instructions said on mine, but I wanted to know if the batteries are being charged, or being discharged, so I put my gages "between" the terminal block on the fire wall, and the wire that went to my batteries to charge them. If the gage is between the alternator and the terminal block, it will only tell you how much the alt is putting out, and not be giving you a better idea of the overall electrical system, as in, the batteries, the alt, the load (lights, horn, A/C, anything using power), and how it all ballances out. If your gage is between the alt and the terminal block, and the gage tells you that it's putting out 30 amps of charge, but you're using 40 amps, but don't know it because of where it's hooked up, the net result is discharged batteries, at a rate of 10 amps.
Anyway, I hope I havent confused you any worse, I am an electrician by trade, so playing with wires doesn't scare me as much as some. I'll look closer at my truck to see exactly how I did it, and maybe give you a little more input, a little more acuratly.
Good luck...
Greg

[ZZ]

I used to hook up ammeters on my older gas GM cars. I wired into one the red wires in the main harness. It was always trial & error to get the right wire. If memory serves me right; there were three red wires.

[moody]

Dieselcrawler:
No not confusing at all. That was about what I was thinking. This would require taking full flow through the ammmeter and back out to the engine compartment. Correct?
I was just suprised by the "Horn relay" instructions. There should be no e- flow unless the horn is being used. Correct?

[dieselcrawler]

Moody,
Not sure why the horn wire is even brought up. The trick is to make sure that there is only one path that the current (electricity) can take, and, yes, to have the ammeter in this line, taking the full ammount current between the battery and the electrical system. A problem I ran into with mine is the large 100 amp alt could over power the 60 amp rated ammeter. I burned up an ammeter that way...
With the dual batteries, and where some wires are hooked up at the starter to get their power, and some at the terminal block on the firewall, make sure you can trace the flow of current, so you get accurate info.
Good luck..
Greg

[moondoggie]

Good Day!

I can't imagine where the horn relay suggestion in your instructions came from - it's one of the most bizarre things I've ever heard. :confused:

I will assume this is a center-zero meter, like cars used to have. If I were adding one to my truck, I'd get the wiring diagram for my truck (I own GM/Helms manuals for everything I own) & find the wire between the batteries & the rest of the vehicle, but NOT including the starter & glow plug circuit. 1) I would exclude the starter because it draws WAY more than the ammeter would probably handle without being destroyed. 2) I would exclude the glow plug circuit because it's unlikely your ammeter would do anything but peg when the glow plugs are on (8 glow plugs will draw 80 - 150 amps, beyond the scale on most ammeters.) This is too bad, because it would be an EXCELLENT way to ascertain the health of your glow plugs & associated circuitry.

This is how ammeters used to be wired into cars, at least every car I

[jcomp]

On some cars, like my Pontaic, the horn relay has a 10ga wire going to it straight from the battery. It is the the main power tap for the rest of the car.

Personally, I much prefer a voltmeter over an ammeter. But to each his own.

[moody]

Thanks for info
...I just got some new wireing diagrams so I can look a bit more for the best spot. I would like to end up with both an amp meter and a volt meter as they both tell me different things.
And yes the horn relay seemed very odd to me so I asked