internally regulated alternator: resistor or no resistor?
 

I have a 72 gmc with an ammeter and no idiot light that I know of. and am switching to an internally reg'd unit for a '78 chevy truck and have read a dozen threads, and some of them say a complicated mess of explanation about idiot lights or resistors and crap.

Above all I'm following this thread: http://67-72chevytrucks.com/vboard/s...d.php?t=800471
I do not believe he says to use a resistor.

Re: internally regulated alternator: resistor or no resistor?
 

I installed a 12SI alternator like in that thread. I did not install any resistors anywhere. My ammeter still works.

Re: internally regulated alternator: resistor or no resistor?
 

My 12SI alternator and my ammeter work perfectly, no idiot light and no resistor.

Re: internally regulated alternator: resistor or no resistor?
 

I sell volt gauge conversions for these trucks. If you run any thing over a 60 amp alternator, the amp gauge will not work correctly.

This will correct that and let you read actual battery voltage.

Contact me if interested.

Re: internally regulated alternator: resistor or no resistor?
 

Will it affect anything if I install an idiot light just for fun?

Re: internally regulated alternator: resistor or no resistor?
 

I am running a battery volt gauge from TBONE1964 with my internally regulated 12si one wire alternator and it works great. I am also using m new wire harness from American autowire and in the instructions they do not supply wiring for the original ammeter when going to a new style alternator. They claim it is unsafe and can cause a fire. I reached out to TBONE1976 and he hooked me up. Looks original and easy to install.

Re: internally regulated alternator: resistor or no resistor?
 

The ammeter indicates the delta between the battery voltage (105) and the alternator output voltage (106). If you have the correct 4 amp fuses installed in the factory harness there's no danger of bad things happening regardless of alternator or regulator type.

Re: internally regulated alternator: resistor or no resistor?
 

I ran a 12Si 100 amp alternator more then 15 years no issues sock ammeter still worked as intended during that time No resistor needed for 10/12si
A resistor is needed for cs130/144 alternator upgrades

Why not look at a cs130 alt they charge way better at idle

Re: internally regulated alternator: resistor or no resistor?
 

The charging circuit has nothing to do with the Ammeter circuit.

That may sound weird or even wrong, but there is only one wire segment that the two circuits have in common. That one wire segment serves double duty. For the Ammeter the wire is a shunt. For the charging circuit, that wire is the charging wire for the Alt/Battery.

You didn't have to add a resister because it is already included inside the original dash wiring harness. The resistance needed for a SI conversion is the same resistance used for the original 10DN external Reg Alternator.

The resistance used is a resistor wire and is part of the wiring harness from the bulkhead connector up to the ignition switch.

The resistance wire is the same resistance wire used even if there was no idiot light on the dash. It's there.

The resistance measures about 10 ohms.

The resistance needed for the CS Alternators is higher and that is why you will see posts about adding a resistor for those installations.

Do not confuse the resistance wire used for the Alternator Exciter circuit and the resistance wire used for the points ignition circuit.
Those two circuits are totally independent of each other.

Re: internally regulated alternator: resistor or no resistor?
 

Wow Richard thank you very much for that straitforward clarification!!!!

If I wanted to add a simple idiot light, I was just going to add a "gauge panel illumination" socket and 194 bulb.

How would I wire this in?


I don't want to deal with upgrading/tearing into the harness for the upped amperage; I don't think I'll need the amps. 63 amps should be enough for adding A/C and a midsized condenser pusher fan.A stereo is probably not gonna happen, and I don't need any other accessory power.
Once this truck is up and running and I actually get things going, I can upgrade to a CS if it proves necessary.

I have learned a lot about cars and discussion forums in the last 12 years and one thing I've learned about forums is everyone will tell you to go nuts with upgrades and mods and how they have experience and if you don't heed their warning your truck will burn. I've learned to take things with a grain of salt. Then again maybe a CS wouldn't even require me to upgrade the harness--maybe I heard that from some paranoid fool, too. https://www.garagejournal.com/forum/...lies/dunno.gif

Re: internally regulated alternator: resistor or no resistor?
 

>> 63 amps should be enough for adding A/C and a midsized condenser pusher fan.<<

????

If you look at the listings for rebuilt 10DN alternators, most are rated at 55 Amps. Some may be higher.


Works for me.

Re: internally regulated alternator: resistor or no resistor?
 

There is a resistive brown/white wire that runs from the igniting switch to the voltage regulator. This wire would be connected to one side of the idiot light bulb, and 12V connected to the other side of the bulb. I don't know if this will work with a 12SI alternator.

Re: internally regulated alternator: resistor or no resistor?
 

Unless I am badly misinformed, the alternator's output will only be whatever the system requires.
So if you have a 100A alternator but your electrical system requires 45A, the alternator's output will be 45A -- not the 100A that the alternator is rated for.

Re: internally regulated alternator: resistor or no resistor?
 

I have a 61A alternator on my truck. I have yet to figure out if that is the original amperage or not. It has factory air and is a Custom Camper, so maybe that's in the mix somewhere. Even when the travel trailer batteries are low and it's charging like crazy, the gauge doesn't peg. This is my own opinion, but I'd expect the shunt wire resistance to depend on which alternator is employed. It makes sense that a 37A alternator would show full scale when peaking out, the same as with a 61A alternator. I guess that it is possible that full meter swing was for the highest charging alternator, and the lower amperage jobs just didn't go full scale when they were maxing out.

Re: internally regulated alternator: resistor or no resistor?
 

According to the factory literature the non AC trucks only have a 37 amp unit, so a 63 is a bit of an upgrade just in case. Figured I'd go with internal reg'd just because they are easier to find in case I had roadside troubles. Also I have a couple on my other vehicles if I needed one immediately.

Honestly I don't even want an ammeter, bit it's more trouble to remove the gauge so I'll leave it.

Re: internally regulated alternator: resistor or no resistor?
 

The 'shunt' is just the 12ga wire from the battery to the alternator. Resistance should be close to zero.

Re: internally regulated alternator: resistor or no resistor?
 

>>There is a resistive brown/white wire that runs from the igniting switch to the voltage regulator.<<

Close, but no cigar.

The resistive brown/white wire stops at the connector terminal on the bulkhead connector. From the engine side of the bulkhead connector, a plain copper wire goes to the #4 terminal of the EX voltage Regulator OR the terminal #1 of the 10SI/12SI Alternator.
The brown/white wire at the connector terminal on the inside bulkhead connector may have a brown copper wire crimped together with it. This copper wire goes to the instrument panel then the Gen light.
The other side of the Gen light goes to ignition switched 12Volts.

The first image shows that when the ignition switch is in the ON position, two parts of the Ign switch is closed and the resistor and the light are in parallel. If the ign sw doesn't have the ACC position, the resistor and the light can be tied together for a single Ign Sw. The second image shows an older style Ign sw with a single contact and the resistor and lamp in parallel.
If there is no Gen Lamp, then the resistor is there and will work fine alone. The second image is shown with a 10SI. You can see that the Batt wire The Exciter circuit and the Sensing wire is the same with either Alternator.

The Shunt for the Ammeter is only the wire segment between the two Ammeter Fuse connections.

Re: internally regulated alternator: resistor or no resistor?
 

I have a full gauge cluster in my truck (not idiot lights). A few months ago I was tracking down a charging issue with my alternator and installed a temporary idiot light on it in an effort to see if the voltage regulator was working correctly. I connected one side of the bulb to the brown/white wire at the voltage regulator and the other side to 12V. The light lit up when the engine was off, but the key was in the run position. It then turned off when the engine was running. Seems like it would be fairly easy to add a light like this to the dash if a person were so inclined.

Re: internally regulated alternator: resistor or no resistor?
 

This is another thing I really appreciate, because this is exactly what I want to do.



Richard or anybody........There is the "welded splice" near the original voltage regulator that technically intercepts the shunt.

It is obvious that modifying this splice or adding to it is a PITA; it would be easier to just tear it apart and install a junction block. I want to do this, as it will give me an easier way to get a hot wire to the future electric fan or A/C system.


Will dissecting this "welded splice" affect the shunt?