3G alternator new or used?

Just unplug C610 and run 37Y (to the right of it) to the fused side of your alternator output.
This can be at the fuse itself, or at the starter relay lug.

Fuse link J and all the wiring attached to the "Fire Plug" go in the trash where they belong.

You say a couple of times "ASI"
That would be: Alternator, Stator, Ignition.
Which one???

You need to keep 904 lg/r going to the new 3G regulator plug, to excite the alternator when the ignition is switched on.
THAT is (I)

Jim had good answers.  But part of the problem is that I've made statements that aren't 100% accurate.  For instance, the shunt doesn't always have to be removed, and that depends on what accessories you have in the truck and what your preferences are.

The shunt is probably good for ~70 amps.  So if you don't have some killer stereo or other serious power-consuming accessory that is pulling power from the cab wiring, then you don't really have to remove the shunt.  You just wire things as shown below with the output of the alternator going to the battery via the starter relay, but w/o the red X above S202 and w/o the relay.  (And you really should have a fuse in that line as well.)

Wired that way the shunt is no longer carrying power to the battery from the alternator, so it doesn't matter how big your alternator is.  However, the ammeter will always show a discharge, and more so when you turn more and more accessories on.

Or, you can wire it exactly as shown, meaning make the cut above S202, add the relay, and replace the ammeter with a volt meter.  In that case the volt meter will show battery voltage when the key is on.

Gary,

I think one of the issues (graphically) is that you depict a 1G, while he has the fireplug, twin o/b wires from it to a fuselink, ect.

Yes, you are absolutely right.  And I need to upgrade the 3G swap page to show both schematics as the '86 trucks came with the 2G.

"Fuse link J and all the wiring attached to the "Fire Plug" go in the trash where they belong."
Thank God for that, I was hoping to not need to replace it J...

"You say a couple of times "ASI"
That would be: Alternator, Stator, Ignition.
Which one???"

Sorry, I meant the original 2G regulator 2-wire A (36, Y/W) and I (904, LG/R) connector. There is no S wire (4, W/BK) on the regulator connector, the S is on the rectifier connector ("fire plug").

"You need to keep 904 lg/r going to the new 3G regulator plug, to excite the alternator when the ignition is switched on. THAT is (I)."

Roger that. The green/red wire I on the new 3-wire ASI regulator conversion pigtail will connect to the old I (904, LG/R).

"The shunt is probably good for ~70 amps.  So if you don't have some killer stereo or other serious power-consuming accessory that is pulling power from the cab wiring, then you don't really have to remove the shunt."

My plans are to add a new radio head unit (with amp, decent speakers etc.), a few extra halogen spot *and* fog lights, a winch, and maybe more down the line. Hence why in an earlier post, I was asking about a >130A alternator.



Is the above a good installation? I saw online, from the ASI, the A (Y/W) can connect back to the B+ post on the alternator. But will this work if I want to retain the factory ammeter, or use the voltmeter (converted from the factory ammeter by "Rocketman" Bob from RCCInnovations).

Since I am going to use the converted voltmeter, should I connect the new A wire to the old 36 Y/W wire, which leads back to S203?

Do I remove Fuse Link J as Jim stated, and where fuse J connected to the starter relay, instead connect the original 655 R/O (ammeter) wire?

Say I do that and I cut the shunt, how is the Rocketman voltmeter going to read the voltage, and how will wire 37 Y feed the cab with power--all from S202, 654 Y/LG coming from the other side of the voltmeter?

I doubt it can/should handle this load, right?

I suppose what is required is to connect Y 37 from S202 back to the battery side of the starter relay, and splice into that 655 R/O and 654 Y/LG, since the gauges of these wires limit the amount of power flowing through them, in turn protecting the ammeter/voltmeter sensitive circuitry.

If the above is correct, isn't that what the shunt can do, or is the gauge unsuitable for the task?

Or am I still lost with two hands and a flashlight?

Vic,
Go ahead and loop the yellow regulator wire to the output stud of the 3G.

But you're going to want the new Rocketman voltmeter wired to key on power.
You don't really want it drawing current constantly with the key out.

Gary would have you wire a relay to tap into the hot side of the megafuse or the starter relay.
My '87 came with a voltmeter, but it is just key-on power, and I am fine with that.

I failed to address your question.

37 Y can connect to the starter relay, just like fusible link J did.
Or, you can go directly to the output lug of the Megafuse holder where the cable going to the relay comes from.

Thanks for clarifying, Jim.

Understood re voltmeter relay.

In my world having an analog representation of voltage after the ignition switch is good enough.

I know that my alternator is putting out 14.35-14.4V unless something drastic happens, but then my idiot light comes on.