What did I do?

[Rex]

Okay, I got a new Autometer voltmeter to replace a very old ammeter in my '74 CJ5. By the way, the jeep was running just fine. So I go through a big hassle trying to disconnect the old ammeter from the dashboard. It had two terminals, one with a + sign. There were two wires connected to it. The other terminal had just one wire on it. Anyway, I get the nuts off the gauge, not easy either, and pull out the old gauge. Next I have to enlarge the hole in the dash for the new bigger voltmeter but I haven't done that yet. So far that's all I have done. I had to disconnect the negative battery wire before removing the gauge, which I reconnected.

Next day I go to start the jeep and I get nothing. No click, no slow cranking, no nothing. I put a trickle charger on the battery and left it overnight and it's fully charged, it's less than a year old too. I try the jeep again today and again, nothing happens. So what did I do? Could disconnecting the old gauge have anything to do with the jeep not starting? Could it just be a coincidence that I'm disconnecting some wires from a gauge and then the jeep won't start? So, any ideas what I did? Or what should I do next now that I know the battery is good?

 

[SteelHeadz]

My best answer is to undo what you did. I would assume that one of the wires connected to the volt gauge is a signal circuit for the starter crank position.

 

[54cj3b]

check that your wires on the back of your amp meter are tight getting good contact also check that your battery terminals are tight

 

[TLCJ5]

The "74 came with a voltmeter not an ammeter so I assume the old one is aftermarket.
An ammeter is wired in series with the battery & a voltmeter is wired in parallel with the battery.
I would think the old ammeter was wired between the voltage regulator & the alternator.Not sure what the 3rd wire is but it could be for a wrning lightWhen you discd the ammeter you opened the ckt & that is why you have no power.(Do your lights or any of you accessories work,I'd expect not)
I would verify continuity across the ammeter & if you have good continuity there you should be able to connect the + & - wires & your Jeep should run.
As for wiring the voltmeter: one side should go to a 12v source & the other side to grd. This will give you a voltage reading across the battery/charging system.

 

[Rex]

First, thanks for the help. I now know what I did. By disconnecting the wiring to the ammeter, which I take it was an aftermarket product, I left open a critical circuit in the electrical system. It's true you do learn something new every day. What I learned is that there is a big difference between a voltmeter and an ammeter. An ammeter is taking the entire flow of electricity from the alternator and so needs a heavy gauge wire to handle it, while a voltmeter is only taking a small amount of current. So they need to be hooked up very differently.

The solution to the problem was simple. All I had to do is take the three wires that went to the ammeter, one was from the alternator, one was from the ignition, and I think the other was from the battery, and connect them all together with another wire and that new wire connects to the voltmeter. So, the solution was simple as soon as I learned the difference between the two gauges and how they need very different wiring. Wiring for a voltmeter is real easy but wiring an ammeter is a lot more difficult and requires much heavier gauge wiring. Now I know what I'm doing getting it installed should be pretty easy. All I have to do now is cut a bigger hole in the dash for the new voltmeter and connect the wires.