How I wired my alternator.

[garyd1961]

I've read a bunch of threads on this and they seem to be somewhat complicated. When I installed my crate engine I rewired my starter and alternator, I switched to an internally regulated alt.
For the alt;
1. I ran the battery wire to the hot wire on my starter.
2. I then looped the red #2 wire to the battery wire on the alt.
3. I ran the brown #1 wire to a keyed terminal on the fuse block with a resister in the line.
I didn't have a resister so I wired a 12v side marker bulb and harness into the line. (If you have a battery light instead of gauge you can use that) I have the bulb placed so it lights my floor up and serves as my alt/battery light. It comes on when I turn the switch to the on position and goes out when the engine starts. It seems to work just fine but I do intend to run the #2 sensor wire to a junction block on my firewall when I get time.

Does anyone see anything wrong with this setup?

[VetteVet]

Originally Posted by garyd1961

I've read a bunch of threads on this and they seem to be somewhat complicated. When I installed my crate engine I rewired my starter and alternator, I switched to an internally regulated alt.
For the alt;
1. I ran the battery wire to the hot wire on my starter.
2. I then looped the red #2 wire to the battery wire on the alt.
3. I ran the brown #1 wire to a keyed terminal on the fuse block with a resister in the line.
I didn't have a resister so I wired a 12v side marker bulb and harness into the line. (If you have a battery light instead of gauge you can use that) I have the bulb placed so it lights my floor up and serves as my alt/battery light. It comes on when I turn the switch to the on position and goes out when the engine starts. It seems to work just fine but I do intend to run the #2 sensor wire to a junction block on my firewall when I get time.

Does anyone see anything wrong with this setup?

Your wiring will work just fine but if you have an ammeter, that will not work.

You should have a brown wire from the firewall block if you are talking about a 1970 chevy. That wire is the exciter wire that ran to the old external voltage regulator. You could have used it since it already has the resistor wire in it from the key switch. It's nice to have the light to indicate charging or discharging if that happens. Here is how I wire mine.

[zosoppp]

Should the fusible link from the battery + to the junction block really be three (3) sizes smaller (18Ga) than the main primary wire (12Ga)?

I thought fusible links were supposed to be 2 Wire Gauge sizes (4 numbers) smaller (so 16 Ga for this case).

[VetteVet]

Originally Posted by zosoppp

Should the fusible link from the battery + to the junction block really be three (3) sizes smaller (18Ga) than the main primary wire (12Ga)?

I thought fusible links were supposed to be 2 Wire Gauge sizes (4 numbers) smaller (so 16 Ga for this case).

Yes that is correct. A 12 gauge wire would have a 16 gauge fusible link.Where did you see the 3 gauges smaller size?

[zosoppp]

Originally Posted by VetteVet

Yes that is correct. A 12 gauge wire would have a 16 gauge fusible link.Where did you see the 3 gauges smaller size?

The diagram you posted indicates the fusible link is 18B (if Im reading it correctly). Although that might be a scanning error or something I suppose.

[VetteVet]

Originally Posted by zosoppp

The diagram you posted indicates the fusible link is 18B (if Im reading it correctly). Although that might be a scanning error or something I suppose.

You have good eyes I never noticed that. I did not create that part of the diagram so I hadn't noticed it. It's possible that the original diagram showed it that way because of the ammeter wire that attaches to the same junction point.

This is from the factory wiring diagram and it shows the FL as a 16 gauge.






I'll have to modify my diagram. VV

[garyd1961]

Originally Posted by VetteVet

Your wiring will work just fine but if you have an ammeter, that will not work.

You should have a brown wire from the firewall block if you are talking about a 1970 chevy. That wire is the exciter wire that ran to the old external voltage regulator. You could have used it since it already has the resistor wire in it from the key switch. It's nice to have the light to indicate charging or discharging if that happens. Here is how I wire mine.


Attachment 1565664

I will see if I can locate the brown wire. I really would like to get my ammeter to working. Thanks for the diagram.

[garyd1961]

I rewired my alternator today. I wired it the way VetteVet showed in post #2. My ammeter still doesn't work but It seems to be charging ok, 14.4 volts. I don't believe the ammeter gauge ever worked since I had the truck, bad gauge maybe. Even if the gauge doesn't work the alternator should still work ok shouldn't it?

[SwitchbladeII]

I have two trucks I am currently working on a 69 and a 70 both have wiring issues which need to be addressed. I am anal about most things redoing old rides and wiring is at the top of my list! Both harness have been hacked like most vehicle of this age. I am in the process of adding fusible links both were missing as well as correcting multiple other issues. One had the amp meter wire lose under the dash live and unfused. The wiring diagrams I see on this post as well as the ones J have show two fuses on the engine side. What type of fuses and what are the values? Any help will be appreciated.

[ray_mcavoy]

Originally Posted by garyd1961

I rewired my alternator today. I wired it the way VetteVet showed in post #2. My ammeter still doesn't work but It seems to be charging ok, 14.4 volts. I don't believe the ammeter gauge ever worked since I had the truck, bad gauge maybe. Even if the gauge doesn't work the alternator should still work ok shouldn't it?

Yes, the alternator / charging system will still operate correctly even if the ammeter is not working. If you wan to get the ammeter working again, start by checking the condition of the 2 inline fuses that are shown on the diagram VetteVet posted. One of them is located over near the battery on the passenger side of the engine compartment and the other is on the driver side (near where the external voltage regulator was originally located).

Originally Posted by SwitchbladeII

The wiring diagrams I see on this post as well as the ones J have show two fuses on the engine side. What type of fuses and what are the values? Any help will be appreciated.

They are both 4 Amp fuses. If your trucks still have the original rubber case fuse holders (as shown below) they take SFE-4 fuses.

[SwitchbladeII]

Thanks Ray! This is a big help I don't think they are still there will check in the AM. If not I can replace them with inline 4 amps. Thanks again.