74 C20 Ammeter

I inherited this C20. Runs & drives. Battery does charge while motor is running. However after looking around and peeking through the electrical and the cluster I’ve noticed the ammeter seems to be wired directly off its terminal posts instead of the printed circuit board connections. One side is ran directly to the battery and the other wired to the brown wire of the alternator. Based off research this seems like something they would do to add an ammeter on an old tractor. I’m curious if this is safe and a proper way to use the ammeter. Thanks

Welcome from Austria. Does the gauge work? If no you should think about a swap to a voltmeter.
This Thread has some info...

https://www.gmsquarebody.com/threads/ammeter-fuse-size.41156/page-2

Wiring diagram for the cluster and firewall junction.

The stock ammeter uses the resistance of the wiring harness as a shunt. There are two fuses under the hood where it connects to the wiring harness. This is good from a safety standpoint, since high amperage does not go through wiring up to the dash. However, as the wiring gets old it’s resistance may change and the ammeter is not accurate.

Conversion to a voltmeter is fairly easy, since the cluster already has places to find power and ground, and you can buy the voltage gauge from LMC or other sources. I followed an article I found on the internet to convert my truck.

ali_c20 said:

Welcome from Austria. Does the gauge work? If no you should think about a swap to a voltmeter.
This Thread has some info...

https://www.gmsquarebody.com/threads/ammeter-fuse-size.41156/page-2

Wiring diagram for the cluster and firewall junction.

Click to expand...

I haven’t tested to see if the ammeter is actually working or working properly. It seems to also just stay a twitch past center towards the Charging side whether the trucks running or not

75gmck25 said:

The stock ammeter uses the resistance of the wiring harness as a shunt. There are two fuses under the hood where it connects to the wiring harness. This is good from a safety standpoint, since high amperage does not go through wiring up to the dash. However, as the wiring gets old it’s resistance may change and the ammeter is not accurate.

Conversion to a voltmeter is fairly easy, since the cluster already has places to find power and ground, and you can buy the voltage gauge from LMC or other sources. I followed an article I found on the internet to convert my truck.

Click to expand...

I’d like to convert to a volt meter and I’ve seen the threads on the conversion of some people just running + and - leads over to the temp gauge however my temp gauge is mechanical and also aftermarket. Currently the the one fuse is blown and the other is connected but again this ammeter is wired directly to its posts and doesn’t connect to the printed circuit board and through the harness. Which is why I’m asking if it’s even safe to do that. It’s been driven like this for years but I also don’t want to be driving a ticking time bomb until I can get a volt meter installed this winter

I would disconnect the ammeter and switch to voltmeter asap. Electrical issues can appear in an instant with old and or hacked wiring. My 0.002$