Wiring upgrades and ammeter operation

[71duster06]

Good morning,
This spring I added 10ga wire from my 60 amp alt. directly to the ammeter through the fire wall, then from the ammeter to the starter relay and a fusable link (common upgrade bypassing the bulkhead connector). So far that seems to be working well as the electric fan and fuel pump have been working fine... shows some charge on the ammeter when everything is running...

I have a 100amp alt. from a police car 360 that i would like to use as i am adding a stereo and larger fuel pump furthur increasing my electrical load.

My thought is to run the recommended 6ga wire directly from the alt. to the starter relay and fusable link while leaving my previous 10ga wire also hooked to the ammeter. My question now is if i add an additional wire that bypasses the ammeter will the meter still show charge/discharge? Sorry for the wordy question but i would like to maintain the original guage operations if possible. I just dont like the idea of a 100amp alt. going through the ammeter only.....

Any thoughts or experience with this would be great.

 

[Mad Dart]

Amp Meter Bypass means means you actually Bypass and do not use the Amp Meter at all. In your case you are still running power through it. Easy way to bypass it is to put both wires on 1 Lug. You can then run your Alt wire to the Starter Relay, Starter or straight to the battery, your choice.

If you are upgrading to 100 amp alternator. You need a minimum of 8ga wire running from the Alt to your choice of landing spot.

I am installing a 100amp Alt today on my Scamp. I have a battery cut off switch on mine so it is a little different. I have my Alt wire going all the way to my trunk "Trunk mounted Batt" to a Ford Relay that triggers power from the Main Batt Cut off to the ignition which triggers the Relay to Close allowing power to feed the battery. Cut the Battery Disconnect and all power from the system and the engine kills. All power is stuck in the trunk with none going forward toward the engine or the dash. So mine may be a little different than yours.

 

[71duster06]

Amp Meter Bypass means means you actually Bypass and do not use the Amp Meter at all. In your case you are still running power through it. Easy way to bypass it is to put both wires on 1 Lug. You can then run your Alt wire to the Starter Relay, Starter or straight to the battery, your choice.

I was hoping that the 10ga wiring that is hooked to the ammeter would still allow the guage to operate even though i add an additional 6ga wire directly from the alt. to starter relay..... i was just curious if someone did something similar...

 

[TrailBeast]

I was hoping that the 10ga wiring that is hooked to the ammeter would still allow the guage to operate even though i add an additional 6ga wire directly from the alt. to starter relay..... i was just curious if someone did something similar...

Partial load on the amp guage wire will only show partial charge or discharge.
So even thought it won't hurt anything, it won't be anywhere near accurate.

 

[67Dart273]

You could do this, you will have to play with wire size. The PROBLEM you will run into, is that if you do not bypass the original bulkhead connector terminals FOR THE AMMETER you will in effect still have part of the original problem

In effect, what you are doing ---on a different scale---is exactly what GM /F/ Mopar did when they all finally went to "remote shunt" ammeters...........that is,..........they all used THE HARNESS ITSELF for the ammeter shunt

The DIFFERENCE is that instead of using an ammeter for the dash instrument, they went to a sensitive meter, a milliameter if you will.


Now the Ferds were far from perfect. One of my (87) Ford Rangers was "so numb" that you had to stare intently at the ammeter when you turned the headlights on and off to see if the damn meter moved!!!

I once "more sensitized" an ammeter on a "Friend's Ford." I dug into the harness, figured out where the "ammeter" wires spliced in (small wires for the remote meter) and ADDED a length of no10 or 12 wire to make the shunt less effective, and force more through the instrument

 

[BillGrissom]

The starter relay stud is BATT+, so running from ALT out to BATT+ bypasses the ammeter. There is a way to have your ammeter still work. You add a series diode pair to the new 6 awg wire. That will let all current flow thru the ammeter until the diode breaks down in forward-mode (~0.75 V drop), which is ~3/4 scale on your ammeter. The excess current will then shunt directly to the battery (thru 6 awg wire). Don't buy 1/4 W diodes at Radio Shack or they will vaporize in 0.1 sec. Read my thread for the PN of a 200A diode, and heat sink it. Don't attempt if you don't know exactly what V = i*R and P = i*V means and how to use, and ignore the posts by a guy trying to argue basic electricity with an engineer.

 

[Map63Vette]

I did essentially what you're talking about I believe. I basically ran parallel charge wires from the alternator to the batter. One was a direct line from the alt to the battery, the other was the stock wiring that went from the alt to the ammeter and through to the battery. I drilled a hole in my firewall and ran the ammeter wires directly since my bulkhead was a little melted though. What others have said is correct. You will still get a reading from your ammeter, but it won't necessarily be correct. It will only read the current that is passing through it, which depending on wires sizes and accesory loadings, will vary.

The tough part with fully bypassing the alternator is that one side of it is the main power point for several interior systems. If you look at a wiring diagram (at least for my 67), there are three or four systems that draw their power from the black side of the ammeter. Disconnecting it disconnects all those other systems, so you have to supply them power somehow.

 

[67Dart273]

Well you don't disconnect it. Read the MAD article. This is an excellent way to go with minimal changes to the car. There's a thread "on here" about converting various clusters to a voltmenter

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

http://www.forabodiesonly.com/mopar/showthread.php?t=119480&highlight=ammeter+conversion

The main problems with original systems is.........

1....The bulkhead connector terminals were never designed to withstand the amperage, even 30A. These same basice 1/4" spade connectors are used in electric furnaces, and even at the nominal 20A of a typical furnace element, they do fail

2....The factory wiring, really was undersized, especially in earlier cars

3....The ammeter, depending on car model, is a poor design and poorly made. The ammeter itself can and does fail in a few different ways

4...."Ma" "herself" knew this........this is why so called "fleet wiring" exists. This is documented in some service manuals as the optional 60A alternator wiring. The ammeter wires were larger gauge, and were run through the bulkhead using separate grommets. The original RED ammeter wire was abandoned. Leads me to believe many (all?) of these were dealer installed.

 

[BillGrissom]

there are three or four systems that draw their power from the black side of the ammeter. Disconnecting it disconnects all those other systems, so you have to supply them power somehow.

All in-cabin loads come off the black "ALT" terminal of the ammeter. The red "BATT" wire goes direct to the battery, untouched by any loads except: transient under-hood (horn) and special high-amp accessories (spotlight, convertible top). That is so the ammeter reads all current flow in & out of the battery (what you want). Thus, the ammeter shows battery charging or discharging, not the current output of the alternator.

Don't disconnect the ammeter leads. If one touches ground - welding torch in cabin. You can leave them in-place, so black is powered thru the ammeter, or connect both on one terminal (better, more solid connection).