Cleaner wiring underhood

[wayno]

So I am trying to clean up the wiring under my hood. I have implemented a distribution block on the core support replacing supplying power from the horn relay and another at the firewall. I have supplied power to the distribution block on the core support using 8 gauge wire - with a 12 gauge fusible link at the battery side of the wire... I have then run 8 gauge power from that the distribution block on the core support to a distribution block on the firewall - I have taken the PIN 2 red wire 12 gauge - added a 16 gauge fusible link and I think powered up the fuse box.

I have been pawing through the FAQs schematics on wiring but a lot of them are for originally wiring to voltage regulator. I think I have translated the remainder of the pins based on various upgrades... new alternator / relays for headlights... and I guess I am hoping someone with some more experience can confirm my assumptions. Thanks in advance.

[TJ's Chevy]

Looks good!

[64shortbed]

Looks good! What I did was I welded up all my holes on the fire wall and ran the wires under the drivers side inner fender by putting braces under the raised part to hold up the wiring. I drilled a big enough hole to run a 7 wire incased trailer wiring to run the head lights, turn signals (mine are in my grill), and horn. As far as my engine wiring I made the wiring come out behind the heater motor. The only wire you see under my hood is the wire for the single wire alternator. All the wires are all hidden under the radiator support covers.

[wayno]

Originally Posted by 64shortbed

Looks good! What I did was I welded up all my holes on the fire wall and ran the wires under the drivers side inner fender by putting braces under the raised part to hold up the wiring. I drilled a big enough hole to run a 7 wire incased trailer wiring to run the head lights, turn signals (mine are in my grill), and horn. As far as my engine wiring I made the wiring come out behind the heater motor. The only wire you see under my hood is the wire for the single wire alternator. All the wires are all hidden under the radiator support covers.

The first challenge was making sure I had the pins right... thanks for the confirmation there... do you have a build thread... would love to see what you did with the wiring.. have some additional challenges as I'm so low that I don't have inner fenders right now... but I did run square tubing as additional bracing to use for support and to route my wiring front to back...

[ray_mcavoy]

I agree ... it's looking good!

The pinout diagram you posted is correct if your truck has a factory gauge cluster. And you are using an original (or OE type reproduction) dash harness for a truck with gauges.

As I'm sure you already know, the brown wire you've labeled "4" originally went to the #4 terminal on the OE voltage regulator. If you're using a 10SI or 12SI internally regulated alternator you can run that wire directly to the alternator's #1 terminal. If you're using a newer CS series alternator, that wire can be run to the alternator's L terminal. However, you'll have to add an additional resistor. The CS series alternators need at least 35Ω resistance in this wire but the resistance wire in the stock (and OE reproduction) dash harness is only about 10Ω.

The black/white wire you've labeled "5" is one leg of the factory ammeter (BATT gauge) circuit. For added safety, I would highly recommend adding a 4 Amp inline fuse to this wire near the distribution block end ... like GM did on the 67-72 trucks. The other leg of the ammeter circuit is a black wire on the engine harness (it connects to the BATT stud on the starter solenoid). Adding another 4A fuse in that wire is a good idea too.

The factory ammeter is an external shunt type meter. It utilized the 12ga wire that originally ran from the battery to the junction on the horn relay as it's shunt. Now that you've replaced that with a considerably larger 8ga wire, you've changed the meter's calibration. On one hand, it won't be as sensitive to low currents flowing to/from the battery. But on the other hand, it will allow it to safely operate at higher than stock current levels.

Now, if you're not planning on using a stock cluster with an ammeter you can disregard all of that. And the black/white wire won't be necessary.

[wayno]

Originally Posted by ray_mcavoy

I agree ... it's looking good!

The pinout diagram you posted is correct if your truck has a factory gauge cluster. And you are using an original (or OE type reproduction) dash harness for a truck with gauges.

As I'm sure you already know, the brown wire you've labeled "4" originally went to the #4 terminal on the OE voltage regulator. If you're using a 10SI or 12SI internally regulated alternator you can run that wire directly to the alternator's #1 terminal. If you're using a newer CS series alternator, that wire can be run to the alternator's L terminal. However, you'll have to add an additional resistor. The CS series alternators need at least 35Ω resistance in this wire but the resistance wire in the stock (and OE reproduction) dash harness is only about 10Ω.

The black/white wire you've labeled "5" is one leg of the factory ammeter (BATT gauge) circuit. For added safety, I would highly recommend adding a 4 Amp inline fuse to this wire near the distribution block end ... like GM did on the 67-72 trucks. The other leg of the ammeter circuit is a black wire on the engine harness (it connects to the BATT stud on the starter solenoid). Adding another 4A fuse in that wire is a good idea too.

The factory ammeter is an external shunt type meter. It utilized the 12ga wire that originally ran from the battery to the junction on the horn relay as it's shunt. Now that you've replaced that with a considerably larger 8ga wire, you've changed the meter's calibration. On one hand, it won't be as sensitive to low currents flowing to/from the battery. But on the other hand, it will allow it to safely operate at higher than stock current levels.

Now, if you're not planning on using a stock cluster with an ammeter you can disregard all of that. And the black/white wire won't be necessary.

Fantastic details ray. I am using the stock gauges and wiring and a 10SI alternator so I think based on your comments I am good on the resistance right? so I was thinking I could use 16 gauge fusible links I have in the garage instead of the 4A fuses on those two wires, do you see anything wrong going with fusible links instead?

[ray_mcavoy]

Originally Posted by wayno

Fantastic details ray. I am using the stock gauges and wiring and a 10SI alternator so I think based on your comments I am good on the resistance right? so I was thinking I could use 16 gauge fusible links I have in the garage instead of the 4A fuses on those two wires, do you see anything wrong going with fusible links instead?

Yes, you should be all set with running the brown wire directly to the #1 terminal on your 10SI alternator. The stock 10Ω resistance wire built into the dash harness will be fine with that alternator.

Unfortunately, 16ga fusible links are going to be too large to provide much of any protection to the stock ammeter & it's wiring. The ammeter wiring is only about 18 or 20ga ... smaller than a 16ga fusible link. And being an external shunt type ammeter, it only takes about 2 amps flowing through the meter itself to peg it full scale. The rest of the current flows through the "shunt" wire.

The fuses in the ammeter wiring will protect against two potential problems. One being a short circuit to ground. The other being an open circuit in the shunt wire (due to a bad connection or blown fusible link). An open circuit in the shunt wiring would force all of the current to flow through the meter itself ... and without fuses that will melt the wiring and likely damage the meter.

Since they'll be located under the hood, weatherproof fuse holders would be a good idea. The 67-72 trucks used glass SFE-4 fuses in rubber cased fuse holders. But some modern blade type (ATO/ATC or mini) fuses in weatherproof holders will work just as well.

[wayno]

Originally Posted by ray_mcavoy

Yes, you should be all set with running the brown wire directly to the #1 terminal on your 10SI alternator. The stock 10Ω resistance wire built into the dash harness will be fine with that alternator.

Unfortunately, 16ga fusible links are going to be too large to provide much of any protection to the stock ammeter & it's wiring. The ammeter wiring is only about 18 or 20ga ... smaller than a 16ga fusible link. And being an external shunt type ammeter, it only takes about 2 amps flowing through the meter itself to peg it full scale. The rest of the current flows through the "shunt" wire.

The fuses in the ammeter wiring will protect against two potential problems. One being a short circuit to ground. The other being an open circuit in the shunt wire (due to a bad connection or blown fusible link). An open circuit in the shunt wiring would force all of the current to flow through the meter itself ... and without fuses that will melt the wiring and likely damage the meter.

Since they'll be located under the hood, weatherproof fuse holders would be a good idea. The 67-72 trucks used glass SFE-4 fuses in rubber cased fuse holders. But some modern blade type (ATO/ATC or mini) fuses in weatherproof holders will work just as well.

Thanks Ray - like to see if I can't fire this thing up next week - so these details are of great help. I really appreciate all your help.

-W