Author Topic: Volt Meter/Altnator Guage upgrade  (Read 413 times)

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Volt Meter/Altnator Guage upgrade
« on: June 07, 2019, 06:20:28 AM »
1985 Scottsdale I am restoring which a few changes. I need to upgrade the alternator, it isn't keeping up with demand. I am upgrading to a 140 amp alternator. I will be changing the charging wire to the battery to 4 Gauge and using a fusible link on that circuit. I am also retaining the routing to the firewall battery junction box. Will this junction box handle the extra amps with now problem. Also being the Alt/Voltage Gauge on the dash basically measure all the electrical system usage will it handle the load, is their any chance of causing a fire with this big an alternator? Thanks

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5349
Re: Volt Meter/Altnator Guage upgrade
« Reply #1 on: June 07, 2019, 08:50:14 AM »
The factory voltmeter will not be affected by the upgrade.

Your plan is to convert to a 4-gauge charge lead, but connect it to B+ via the factory firewall junction block?  Does your plan include upgrading the 12-gauge jumper between the junction block and starter to 4 gauge cable?  Why not just route alternator output directly to the battery and bypass the factory routing/wiring? 
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: Volt Meter/Altnator Guage upgrade
« Reply #2 on: June 07, 2019, 03:40:09 PM »
Yes, I am upgrading the entire route to 4 gauge. So the cable from the alternator will be 4 gauge with a fusible link to the junction block, and then 4 gauge from junction block to starter. I suppose going straight to battery is also a way to go.

Offline Captain Swampy

  • Junior Member
  • ***
  • Posts: 500
  • Wisconsin
Re: Volt Meter/Altnator Guage upgrade
« Reply #3 on: June 07, 2019, 06:09:54 PM »
What size fusible link? Doesn't pay to use 4 gauge and choke it with the stock fusible link.
1987  350TBI 700R4  4X4  4.56 gears  33" BFG All Terrain


http://forum.73-87chevytrucks.com/smforum/index.php?topic=32209.0

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: Volt Meter/Altnator Guage upgrade
« Reply #4 on: June 07, 2019, 06:46:28 PM »
The biggest fusible link I can find right now is 10 gauge, trying to find 8 gauge, but not buying 25 of it to use 6.   


Sent from my iPhone using Tapatalk

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5349
Re: Volt Meter/Altnator Guage upgrade
« Reply #5 on: June 07, 2019, 09:08:43 PM »
Regarding the 8-ga link, don't limit your search to the Internet or "traditional" sources.  Try a local electric shop, well driller, or electrician for the link.  Some Class 8 truck dealerships may be able to supply a prefabbed 4-gauge cable with the 8-ga link already installed as a service part; speak with the service department electrician.


Adhering to your original plan:

The alternator will not need to produce 140 amps for very long before the battery begins to recover and the charge current decreases significantly.  As such, the factory firewall junction block should tolerate the transient current load as long as both 4-ga cables share the same 1/4" stud of the junction block.  Or, upgrade to a 5/16" junction block.  Be careful that the cable ring terminals are properly sized to fit the stud.  Specify SGX battery cable due to its superior heat and chemical tolerances.  Install two fusible links: one in the charge lead where it connects to the junction block and one in the junction block-to-starter jumper where it connects to the 3/8" starter solenoid stud.  Mechanically crimp and then solder the terminal ends to the cables using 60/40 or 70/30 rosin core solder.  Then use quad-wall, adhesive lined, polyolefin heat shrink to insulate the 4-ga cable to its terminal end junctions.  Route the 4-ga cable through Thermo-Sleeve in the vicinity of the starter to protect it from radiant exhaust heat.  Use 2-ga SGX stranded copper starter and ground cables to connect the battery to the starter and engine block.



An alternate direct routing to battery:

Route the 4-ga SGX cable directly to the battery through an 8-ga fusible link installed at the battery connection.  Optionally replace the 12-ga starter-to-junction block run with 8-ga SXL cable protected by a 12-ga link at the starter solenoid.  If you anticipate the potential for supplemental B+ taps directly off the battery in the future, install a 3/8" (10 mm) junction block on the radiator support adjacent to the battery.  Route the alternator 4-ga charge lead protected by the 8-ga link directly to the 3/8" (10 mm) junction block.  Jumper battery B+ to that same junction block stud using a short length of 2-ga cable; the starter cable will still connect directly to the battery as before.

Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: Volt Meter/Altnator Guage upgrade
« Reply #6 on: June 08, 2019, 09:23:31 PM »
Thanks I get started on the changes....

Offline 75gmck25

  • Frequent Member
  • **
  • Posts: 381
  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: Volt Meter/Altnator Guage upgrade
« Reply #7 on: June 09, 2019, 05:25:16 AM »
Fusible links are usually 4 numbers (two gauge steps) bigger than the wire they protect, so an 8 gauge link protects a 4 gauge wire.  However, I don't think I've ever seen GM use a charge wire as large as 4 gauge, even in the newer trucks with much higher amp alternators.    I don't think a 10 gauge link will be any problem for you.

Bruce

Offline Johnret

  • Newbie
  • Posts: 25
  • Newbie
Re: Volt Meter/Altnator Guage upgrade
« Reply #8 on: June 09, 2019, 05:30:08 AM »
Thanks for the response, it looks like I am going to be using a 10 gauge fusible link. Can't find 8 gauge anywhere unless I buy a spool of 8 gauge. I think I am going to back down on the 4 gauge wire option and try it with 8 gauge wire and the 10 gauge fusible link. I don't think my truck will ever have a need to get above 90 amps for any period of time. So I may be using some overkill with 4 gauge. the new Alternator is rated at 140 amps, so if it does blow the fusible link I'll know I have to go bigger.
« Last Edit: June 09, 2019, 05:32:19 AM by Johnret »