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I am doing some wiring changes to a 79 Bronco. Right now, I have a yellow/black coming from the instrument panel. from what I can tell, it goes to the yellow (A) on the voltage regulator. This wire coming from the cluster from one side of the ammeter. It has +12 constantly and when I connect it to the V/R, the V/R gets hot, and I believe the meter pegs to the discharge side. The red/orange wire going to the other side of the meter goes to a + battery connection. Seems to me, I either have a bad ammeter, or the shunt. Any thoughts?
I don't recall mine moving, it just stays neutral. I long ago added a volt meter to actually see what goes on. It is wired direct from the battery pos via a fused dedicated lead through a relay the is triggered via ignition switch run. Below is 2014 and then 2023. 13vdc or so is good.
It never even flickered when I would activate flashers or pull the head lights on or step on the brake, like I would see in my police cars and other personal cars. Maybe I was expecting too much of it.
I am doing some wiring changes to a 79 Bronco. Right now, I have a yellow/black coming from the instrument panel. from what I can tell, it goes to the yellow (A) on the voltage regulator. This wire coming from the cluster from one side of the ammeter. It has +12 constantly and when I connect it to the V/R, the V/R gets hot, and I believe the meter pegs to the discharge side. The red/orange wire going to the other side of the meter goes to a + battery connection. Seems to me, I either have a bad ammeter, or the shunt. Any thoughts?
The 2 small wires that connect to the AMP meter go the the Shunt.
One wire is connected to each end of the shunt wire. The Shunt wire has a very small amount of resistance. The AMP METER senses the small voltage change across the SHUNT and causes the needle to move off center, charge or discharge, depending on the direction of the current.
It only measures current going into OR out of the battery.
If you don't want to figure out how to wire it correctly, just switch to a volt meter.
I am sure that there is a "How To" regarding this. Maybe someone can post a link.
Here's the one for the 1980 to 1986 trucks. https://www.ford-trucks.com/forums/1...olt-meter.html
The idea is the same for your truck, but the wiring info (colors and location) is different.
Swapping the AMP meter to a VOLT meter is often needed when you do wiring mods, like head light relays, as the AMP meter doesn't read correctly.
If you upgrade the alternator this will usually bypass the shunt also.
Jim
Last edited by JimsRebel; Dec 9, 2025 at 11:15 AM.
The 2 small wires that connect to the AMP meter go the the Shunt.
One wire is connected to each end of the shunt wire. The Shunt wire has a very small amount of resistance. The AMP METER senses the small voltage change across the SHUNT and causes the needle to move off center, charge or discharge, depending on the direction of the current.
It only measures current going into OR out of the battery.
If you don't want to figure out how to wire it correctly, just switch to a volt meter.
I am sure that there is a "How To" regarding this. Maybe someone can post a link.
Here's the one for the 1980 to 1986 trucks. https://www.ford-trucks.com/forums/1...olt-meter.html
The idea is the same for your truck, but the wiring info (colors and location) is different.
Swapping the AMP meter to a VOLT meter is often needed when you do wiring mods, like head light relays, as the AMP meter does read correctly.
If you upgrade the alternator this will usually bypass the shunt also.
Jim
I do want to figure out how to wire the existing ammeter.
Are you currently using a stock 1G Ford alternator?
Do you plan on any alternator upgrades? Like a 3G ALT?
Have you changed any wiring between the alternator and the battery?
The AMP Meter shunt wire is between the alternator and the battery. The battery side is connected to a fusable link which is attached to the HOT side of the starter solenoid. At the splice points, on each end, the small wire that feeds the AMP Meter is attached.
The other end of the AMP Meter shunt is connected to the alternator output.
Remove the tape from the wires and take some photos, showing the splice points.
Good luck, Jim
Can anyone tell me where the shunt is physically located. I read it is in the wiring harness, but where?
A shunt doesn't necessarily mean a "thing" like the word "fuse" might mean a "fuse". A shunt type ammeter is just measuring current flow direction across a selected section of the wire harness, it does not carry the whole load through it's body. It can be "marked" in calibrations: but really it depends on it's sensitivity. The section of wire harness acting as a shunt could be 5 inches of 5 feet in length and it is sized to carry the full load of charging / discharging the battery. There are ammeters that have all current directly flowing through the meter mechanism, they are often test instruments, they aren't just sensing current flow, they are measuring it all.
Follow the 2 small wires towards the alternator, you should be able to locate the original shunt wire as the 2 small wires connect to each side of it.
Are you sure the original shunt wire hasn't been removed.
Jim
No. As a matter of fact, I think it has been removed. there was a lot of, shall I say, wiring hacks in this vehicle. I have fixed most of them but this one has me perplexed. Is the shunt a small black wire that plugs into the I/P connector?
Last edited by Tommy Martin; Nov 6, 2025 at 05:16 AM.
Here a photo of an 1980 - 1986 alternator style wiring harness. This is a 1986 G2 ALT harness.
On the left you will see a FAT black wire with large round rubber splice points at each end. At each splice point there is a small wire attached, yellow or red. These feed the AMP Meter connections.
I really doubt if you still have any original wiring in the alternator wiring harness.
At some point you're going to have to give up and just switch to a VOLT Meter.
Good luck, Jim
Last edited by JimsRebel; Nov 6, 2025 at 10:40 AM.
Jim, I have reached out to RCC inovations, via phone call and email and got no response. Personally, from what I see on the website, the guy is a real JERK. I can't find anywhere else that seems to do it. I think I am going to have to use a shunt with the original ammeter. Is there any way I can find out what the resistance on the shunt is supposed to be? I can wire one in, no problem, I just need to know what to wire in. I thank you so very much for your help with this issue.
Ammeter ?
