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Alternator Wiring Q

nvrenuf

nvrenuf

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I’m using the wiring diagram below. The alternator I’m using is a stock type 105a CS130 unit for a ‘91 TBI Blazer.

1) Should the “switched ignition” wire have a fuse? If so, what size?

2) The diagram shows a fuse in the battery wire, I was going to run straight to the battery with this wire, ok? What size fuse? If it’s a large amp fuse, suggested types?

20BEA9E3-DCBC-493B-854D-D2E0F747DD5D.jpeg
 
That is normally the fuse link protecting that circuit. 2 12ga in series. If the reg wire is fused it would covered by the gauge fuse, 20a
 
nvrenuf said:
I’m using the wiring diagram below. The alternator I’m using is a stock type 105a CS130 unit for a ‘91 TBI Blazer.

1) Should the “switched ignition” wire have a fuse? If so, what size?

2) The diagram shows a fuse in the battery wire, I was going to run straight to the battery with this wire, ok? What size fuse? If it’s a large amp fuse, suggested types?

View attachment 390613
Click to expand...
Be aware that the sensor wire in that diagram is “wrong”. Technically it’ll work but the sensor wire should really go to the distribution block or somewhere that has the bulk of the electrical load so the alternator can more accurately regulate the voltage.
 
First, I must apologize as I was tired and in a hurry when I made this post so I wasn't paying attention.

The "switched ignition" wire already has a fusible link built in so I only need to provide the appropriate power.

bp71k5 said:
Be aware that the sensor wire in that diagram is “wrong”. Technically it’ll work but the sensor wire should really go to the distribution block or somewhere that has the bulk of the electrical load so the alternator can more accurately regulate the voltage.
Click to expand...

@bp71k5 if I pull switched power from the main fuse panel, will that work correctly?

@Wes Harden & @bp71k5 For the main "battery" wire, could I run it straight from the alternator to the OE junction clock on the firewall? This is powered by a wire from the starter that has a fusible link built in. Do I worry about the (unknown) rating of this fusible link? - OR- Should I run it straight to the battery with it's own fuse / breaker?
 
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nvrenuf said:
First, I must apologize as I was tired and in a hurry when I made this post so I wasn't paying attention.

The "switched ignition" wire already has a fusible link built in so I only need to provide the appropriate power.



@bp71k5 if I pull switched power from the main fuse panel, will that work correctly?

@Wes Harden & @bp71k5 For the main "battery" wire, could I run it straight from the alternator to the OE junction clock on the firewall? This is powered by a wire from the starter that has a fusible link built in. Do I worry about the (unknown) rating of this fusible link? - OR- Should I run it straight to the battery with it's own fuse / breaker?
Click to expand...
I think you can take switched power from anywhere you want, as long as it’s switched off when the key is out.

The wire I’m talking about it the “sensor” wire which is how the regulator knows to increase/decrease the voltage output to the system. By connecting it right back to the alternator like that diagram shows, it’ll always be reading 14.4V or whatever the alternator is outputting, which turns your alternator into a “one wire” alternator. The purpose of that sensor wire is to measure the real voltage downstream in the system after any voltage losses due to wire lengths and changing battery charge level. I’d recommend running it to the OE junction block if that where most of the electrical components get their power from.

Take a look through here even though it’s for older GM vehicles, it explains it really well.

Madelectrical http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml
 
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Also, the fusible link (if you keep it), needs to be at least one wire gauge smaller than the wire it is protecting. If you are upgrading wires, best to upgrade the fusible link as well.

I actually hate them because it’s hard to tell when they’re bad because you can’t see they are blown. My preference is using a larger wire along with a fuse, but that’s sometimes easier said than done.
 
Yes the junction block is acceptable. Iirc the factory uses the junction block.
Needs good clean connections throughout for peak performance.

I agree with @bp71k5 the sensor wire needs a different source, and should be protected by a fuse.
 
THNAKS guys! I totally blew right past which wire you meant, all this info is a HUGE help! Thanks again!
 
@Wes Harden @bp71k5 I don’t have any available 12v ignition ports on the OE fuse box but I do have an opening in the six fuse panel I added for accessories.

If I run the alternator wire from that spot, what size fuse will it need? I’m inclined to go 20a like a “typical” circuit but I really do know what I need.

Also, since I only have 3 unused ports I’d like to save a couple for future stuff (radio maybe, etc). Would it be ok to pull both of the alternator wires (switched and sensor) from the same port? Just wondering since the sensor wire is just “feeling” the voltage level rather than pulling power. (if I understand this correctly)
 
If it was ok to run switched and sensor from the same feed, they would have wired them together in the alternator.
The sensor should be between the battery and the fuse panel feed.
 
nvrenuf said:
@Wes Harden @bp71k5 I don’t have any available 12v ignition ports on the OE fuse box but I do have an opening in the six fuse panel I added for accessories.

If I run the alternator wire from that spot, what size fuse will it need? I’m inclined to go 20a like a “typical” circuit but I really do know what I need.

Also, since I only have 3 unused ports I’d like to save a couple for future stuff (radio maybe, etc). Would it be ok to pull both of the alternator wires (switched and sensor) from the same port? Just wondering since the sensor wire is just “feeling” the voltage level rather than pulling power. (if I understand this correctly)
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That sensor wires doesn't need to be fused. You can put it anywhere technically, but you'll get better performance (how much is debatable) if it goes to the junction block that powers the rest of the vehicle.

The switched power for the alternator just needs to turn on when the key is on. Your current alternator must have an existing wire for that?
 
A lot of the wiring was deleted or modified when the PO removed the TBI (this is why I replaced the dash harness with a custom made super minimal harness). To add insult to injury, I pinched a wire reinstalling the steering column and the resulting dead short melted some of the alternator wiring that was there. This is when @ktmoutfront saved me with his magical alligator clip.
 
The fuse doesn't need to be large.
10 amp would be sufficient.
The key hot is not for high loads, only control of regulator.
 
nvrenuf said:
A lot of the wiring was deleted or modified when the PO removed the TBI (this is why I replaced the dash harness with a custom made super minimal harness). To add insult to injury, I pinched a wire reinstalling the steering column and the resulting dead short melted some of the alternator wiring that was there. This is when @ktmoutfront saved me with his magical alligator clip.
Click to expand...
Ah. The keyed hot maybe can be shared with something else that’s already fused? I’d have to trace mine down but I’m sure I don’t have a dedicated alternator fused power lead.
 
Great, thanks again guys! I appreciate all the help and patience, I hate wiring. lol
 
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