The answer is, specifically, it depends.

Some trucks seem to be able to get away with unplugging and removing the entire alternator and external regulator harness, and popping in a 3g setup. Others, have to have some wires spliced over. Do it wrong, and get out the fire extinguisher. I think different years used the same wiring, but had the pickup points for the gauge in different spots, so it's possible to keep it in the loop. I'm not positive because while i've done a 1g to 3g conversion on another vehicle, I haven't messed with that many dentsides. From what I can tell on my 79, simply unplugging the alternator wiring won't work, as some if not all of the truck is rendered dead by doing so. There are ignition switch power feeds in the same connector that the ammeter is wired through, so proceed with caution. I have yet to find a definitive post addressing this anomaly. When I do this truck, I will be sure to document it.

Oh and in your initial question you asked is it smarter to do them at the same time. To which the answer was yes.

Then hiu asked why to which you didnt get the answer you were looking for.

Then you asked if the ammeter was removed from the circuit why do the voltmeter conversion. So you didnt ask the right question.

Is it smarter? Yes, because the wiring will have to be modified going to the ammeter circuit to accommodate the voltmeter. Might as well do all the mods at once. But the cant be done and keep the current ammeter. You can do them later, but may be redoing some of the wiring.

Hope this puts the topic to bed.

 

I still like the aftermarket ammeter guts behind the Ford face and needle... Then hook it up how the aftermarket instructions say.

 

Thanks to Highorder 77, I now have a functioning 3G alternator AND functioning factory ammeter. You guys are amazing and so helpful! Thanks for all the information and patience! Happy Spring!

 

Sorry I missed the fun. At one time there was an entire write-up on how to retain the factory ammeter and have it read from a more powerful alternator. The writer gave specific lengths of wire for the shunt and everything. Seemed overly complicated to me at the time, but at least someone had gone to the trouble.
Maybe it wasn't here, but perhaps over on the old ProjectBronco website? Can't remember, but I did print it all out to save it. So it's cleverly hidden in a file somewhere.
Glad you figured it out msalander.

Any easy helpful hints you can give as to what route you took? As you found out, yes you can simply install a 3G with new energizing and sensing wires, along with a new dedicated charge wire, with the old stuff disconnected the ammeter is not even in the loop anymore.
But still curious how you accomplished your install.

Thanks

paul

 

I can't say I have any "helpful hints." Highorder77 was an invaluable resource and answered all my questions, literaly. I had harvested a complete wiring harness from a couple of different mid 90s Fords. I removed my '77 wiring from the 3-prong and 2-prong factory connectors and deleted the external voltage regulator. The new wires use the factory plugs, so the install looks pretty clean. I do not have electric choke assist on my carburetor, so I skipped the wiring for that. Highorder77's write-up includes gauge sizes so I built the 3G harness wtih new wires. I wasn't concerned with matching up factory wiring colors. I used a 6 gauge, 9 foot shunt wire. There is plenty of room for this under my plastic intake tube and the radiator core support, on top of the rail and the charcoal cannister. I had to re-clock my 3G alternator. I also needed to add a shim behind the pulley so the pulley wouldn't rub the case. The pulley and belt line up really well. No belt squeal at least not yet. I wanted to keep my factory ammeter. I know a lot of folks have converted to voltmeter. But with the longer shunt wire, the needle on the Ford ammeter actually moves and I can tell at a glance that my charging system is functioning well.

 

I figured it was possible.

I'm guessing that the longer shunt wires do something to attenuate the current, and thereby protect the gauge?

 

I believe that's the reason and result. But in reality, with so little current actually passing through the gauge, I wonder if melting gauges is even a thing?

In the writeup I referenced he used small wire, but changed the lengths to change the current flow to the gauge. Took some time and multiple experiments to get it to read where he wanted, but the end result was pretty slick and predictable. Nice to have a working gauge again!

Too bad the shunt systems on Fords were so inconsistent and unreliable. Could have been a decent setup.
Dakota Digital has ammeters that are remote-reading types, where you place an inductive loop out in the engine compartment around the main charge wire, and that sends a signal to the gauge in the cab. Seems like a great idea, but only comes in their old-school blue digital readouts. I like the newer style instrument clusters, but am still tempted to go with blue luminescent just to integrate an ammeter again!
Yeah, I know... Volt-meters are the way to go. But I grew up using both and still like to use both to keep tabs on things.

paul

 

Yeah, I'm not going to pretend to understand all the specifics about auto-electrical circuitry. Highorder77's write up included a lot of technical/electrical stuff that's beyond my understanding. In his write up he clearly states one may need to experiment with the length/gauge of the shunt wire. I copied him and used a 6gauge, 9 foot shunt wire. This is bolted through a separate eye connector than the main alternator power wire. I used a 175a mega fuse to protect the system and a 1a blade fuse to protect the ammeter wire. All my questions were answered in the write up and personal correspondence with Highorder77

 

Sounds great. Glad you're up and running with the new (and arguably better) charging system.
I'm still running an old-school large-case 1G at 105amps rating and love them. It has all worked well for me for years and I like the "cleanliness" of using original factory stuff. But I tell ya, once it goes out the next time I'm going 3G all the way.
Just no more real reasons not to I don't think.

Paul

 

It takes only a 9 volt battery to make the ammeter needle sweep immediately all the way to one side.

I think the ammeters are a little better than a voltage gauge. The ammeter is always powered, so it can tell you that you have a dead battery before you turn the key or notice the domelight isn't coming on. Volt meters are only powered when the ignition or accessory circuit is powered.

 

Good point. And I've used that to good effect several times when I noticed a drain showing on the ammeter when nothing else was turned on. Saved my bacon more than once with my Bronco I bet.
Though I can't say as I've ever seen my '79's ammeter move when nothing else was going on. But then again, that's probably a good thing!

Paul

 

When I did my 3g upgrade I had my old amp meter converted by RCC that Rich put the link to. Works really nice!

Later, Shortbox4x4

 

I too sent my amp meter to rcc,,,,,I have a printed circuit back of console,,,,not sure on his directions on cutting and folding printed circuitry onto itself ,so i have not crossed that bridge yet

 

• What do you mean by 'cut around and peel back the printed circuit' in the installation instructions?
• After 1968 Ford started using a mylar circuit card on the back of the clusters to connect (wire) the gauges instead of actual wires. Since you cannot use the ammeter wiring you need to cut around the two copper circuits for the ammeter and fold that part of the mylar printed circuit back away from the volt meter studs. Then you can attach regular wires to the volt meter. Click here for a sample picture.
  Answered my own question