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Old 09-08-2019, 03:57 PM
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Wiring up Amp Gauge on a 100 Amp Alternator

OK - 63 Belair and installed a one wire 100 Amp Alternator, I am using 4 Gauge wiring Alt to Battery and adding a 4 Gauge Ground wire from Alternator Mounting stud to Engine Ground.
NOW MY ISSUE BEGINS!
I purchase years ago a standard 3 Gauge set that I am adding, Water Temp, Oil Pressure and Amp Gauge. The Amp Gauge.
Gauge shows Neg 60 to Zero to Pos 60. See Photo.
Two Questions - Since I have a 100 Amp Alternator, will this gauge Not Work?
So, if this gauge will still work or not and or if I need to purchase another gauge my Second Question is:
Since the 100 Amp Alternator calls for 4 Gauge wire - Would I need to Run the same 4 Gauge wires to the back of the Gauge?????
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Old 09-08-2019, 04:06 PM
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Or since the purpose is just to make sure its charging, would I be better off just adding a Voltage Gauge?? with 12 or 14 gauge wire.
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Old 09-08-2019, 05:20 PM
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Quote:
Originally Posted by Sleppy View Post
Or since the purpose is just to make sure its charging, would I be better off just adding a Voltage Gauge?? with 12 or 14 gauge wire.
This^^^

I'm not even sure you could find a 100 amp ammeter.
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Old 09-08-2019, 05:23 PM
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I just figured that out - I am going with just a Voltage gauge.
I couldn't figure out how to delete my questionable question!
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Old 09-09-2019, 02:59 AM
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Run your 4 gauge battery along the frame to the starter, then go up the backside of the block to a firewall mounted isolated stud.

This stud you then use to power your fuse panel.

You run your 4 gauge alternatior BAT wire over the intake and back to this stud.
You run your S (sensing) wire which tells the alt to charge or not back to this stud.

You run your 14-16 wire to the gauge off the stud. This lets you see any drops in voltage.

For electric fans and headlight use fused relays powered directly off one of the battery terminals and switched on by factory wiring.


Using a firewall mounted stud and wiring like I mentioned keeps things clean and keeps the wiring away from heat / moving items.

Starting wise your battery is only powering the starter. If you have a high compression engine you only need to increase that 7 or so feet of 4 gauge to 2 gauge.

Charging wise the alternatior is powering your car first which means less drop in voltage. Then it is powering the starter then battery.
On your fans and headlights those will see a momentary drop in voltage when first turned on. But by keeping the wiring 10 gauge and short at less then 3 feet powering relays then having full voltage on the switch side. Your far better then many setups that have the relays located away from the heavy draw items with that 4 gauge wire quickly restoring full battery voltage.



I make my own isolated stud using 1/2" threaded rod, some nylon washers, and a section of 1/2" id heater hose. I use a step bit and drill a 3/4" hole in the firewall. I put this hole where it is accessible from the inside usually by removing the radio. I cut the threaded rod to 5". Then using grease slide 1" of the hose over the threaded rod so it is centered. Then I wiggle the 3/4" hose into the 3/4" hole so it is centered. Slide the nylon washers over the rubber hose and against the firewall. Stack the nylon washers so they are 5/8" on both sides of the firewall. Now you take 2 nuts and spin them down so the nylon is crushed against the firewall. Your not crushing the hose. By crushing the nylon against the firewall your "suspending" the rod within the hose and the hose will not dig into the firewall over time. So torque down those nuts tight. I put around 80ft/lbs into them while holding the other nut while keeping the rod centered then switch it around. Once that is done you get a metal washer with a lock washer then you can stack 3 to 5 copper ring terminals onto that lug(keeping them from rubbing the firewall)then you tighten down a nut on top while holding the nut behind it. This also makes a great through terminal meaning you can eliminate that junk factory style(not waterproof) multiblade blade setup for a single 4 gauge wire powering a easy to reach fuse panel located in a easy to reach location such as the back of the glove box, ash tray, or center console.
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Old 09-09-2019, 04:12 AM
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Older cars used to have a full current flow amp gauge in the dash, but they later figured out how dangerous this could be to have all that current going to and from a dash guage. Then manufacturers switched to ammeter gauges that used a shunt to measure voltage drop between two points in the harness and display it as amps. This design was also troublesome because it often got very inaccurate as the wiring aged and shunt resistance changed. At that point manufacturers switched to using voltage gauges as a simple alternative. Stick with a voltage gauge and it will be much easier to wire and maintain.

Bruce
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Old 09-09-2019, 08:16 AM
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IMHO a waste of $$$. Your alt will seldom provide 100 amps, and only briefly.

A Volt meter will tell you more.

But if you must, go to West Marine's web site, search Amp meter and amp meter shunt. The Shunt is the KEY. No high current wires will be routed to the gauge, like the old cars. Be sure to fuse the wiring , both, from the shunt to the meter. Minimal wiring is required.

The shunt is to placed in the battery ground wire, the closer to the battery the better. . A body ground & ETC. must be connected on the down side of the shunt so it measures the all loads, head lights as example.

The Shunt has no effect on sensitive electronics and the shunt is a very low resistance. Typically $70 for marine quality. Blue Seas is the best maker.

Michael.
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Old 09-09-2019, 08:17 AM
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Here ya go, West Marine Shunt link,, mfg by Blue Seas..

https://www.westmarine.com/buy/blue-...1?recordNum=22
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Old 09-09-2019, 10:53 AM
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I see a post that calls for a lot of work for a volt gauge......there are easier ways..........


Any hot wire on the car will work. Cigarette lighter wire in this case, changed to key on hot.



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Old 09-10-2019, 12:59 AM
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I have ran those lighter ones in the past in my around town hooptie's(No parking lot incidents or theft driving my hooptie's) that only had an idiot light.

They work good for checking things. But are annoying at night. A bit of window tint dims them to a non distracting level.
You need to be a bit careful also as they can become hot. Some lighters also don't turn off with the key so plugging /unplugging will become an inconvenience fast.
For checking things they are good. But they dont replace an actual gauge.
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Old 09-11-2019, 07:10 PM
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Quote:
Originally Posted by Sleppy View Post
I just figured that out - I am going with just a Voltage gauge.
That's the right way to do it. You don't want all that amperage running through an instrument panel gauge.
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Old 09-11-2019, 08:47 PM
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Volt Meter Ditto.....
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Old 09-12-2019, 03:43 AM
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Quote:
Originally Posted by cerial View Post
I have ran those lighter ones in the past in my around town hooptie's(No parking lot incidents or theft driving my hooptie's) that only had an idiot light.

They work good for checking things. But are annoying at night. A bit of window tint dims them to a non distracting level.
You need to be a bit careful also as they can become hot. Some lighters also don't turn off with the key so plugging /unplugging will become an inconvenience fast.
For checking things they are good. But they dont replace an actual gauge.

Works fine. I changed power to key on hot. Worked fabulously diagnosing the regulator malfunction in my alternator. The numbers were going up and down rapidly. Now, the numbers stay at a constant. 13 bucks for an alt gauge and you even get a free thermometer.
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Old 09-12-2019, 11:20 AM
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Quote:
Originally Posted by Sleppy View Post
I am using 4 Gauge wiring Alt to Battery
you have already bypassed any means of installing an ammeter, just go with a volt gauge
ammeter needs all power in and out going thru the gauge, not very safe under the dash
volt gauge only needs a reference wire that can be small and from almost any keyed source
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