The Stovebolt Site Forums The Shop Area The Electrical Bay Ammeter & One Wire Alternator?

I'm going to be installing a one wire GM Alternator in my 56. Will my stock Ammeter still work ok? On my 42, I retained the generator (switched to 12V) and ran the fusebox main lead from the foot switch to the ammeter and from the ammeter to fusebox. On the 56, I planned to run the battery + lead to the solenoid, then a lead to the ammeter, then from the ammeter to the fusebox. The one wire alternator would hook in at the solenoid also. I think this will work ok, but thought I'd check it with the experts before I actually wire everything. BTW, I am going with American Autowire's Highway 15 harness. Looks really good!

It seems to me that the ammeter is bypassed by the charging circuit in this configuration and would only show a discharge, since it's only connected to the loads beyond the fuse panel. I would think the alternator should be connected somewhere on the other side of the ammeter from the battery, but maybe I'm missing something here.

Clint Lovell,

It sure seems perfect to me. The ammeter is between the load (fuse panel) and the battery, so it should show any charge, or a draw.

Stuart

Honestly, I left mine off...I used a alternator for a 79 nova (one wire)didn't hook up to the gauges...Even though they are new old gauges rated for 12 volt...I wasn't sure...thought it might catch fire....

Clint,

Check out this diagram for wiring a one-wire alternator (and ignore the spelling and quality of the drawing).

I have used this wiring for over 7 years with no problems at all (6v '54 converted to 12v). The lead from the alternator goes through the ammeter to the battery. The ammeter works fine.

Tim

Clint Lovell,

Tim is right...I was wrong! The ammeter must be between the alternator and battery with the load (fuse panel) on the same side as the alternator.

I think Waldo was on it too!

Stuart

I have GMC gauges in my 51 and the ammeter shows 50 amps discharge/charging. I am running a Delcon 10 SI alternator which puts out 72 amps maximum. I am not currently running the alternator output through the ammeter because I thought 72 amps would burn it up. I don't care if the ammeter gets 'pegged' right after startup but will it be able to handle the current my alternator puts out?

Any thoughts about this?

I've got a hi-output alternator on my 58 with the stock gauge, and have never seen it pegged - if the alternator starts putting out 72 amps with no loads to use it, the gauge would be the last thing you'll be thinkin about

Bill

Racecarl,

Your alternator might have the capacity to put out 72 amps, but that won't happen unless your old truck has the need for this amount of power.

A analogy would be a huge water tank holding millions of gallons of water. Hook a little garden hose to it with a little flow meter in line, and NO problem. The garden hose will never use the full capacity available to it.

Amperes is a measurement of current flow. If nothing in your truck demands tons of power, little current will flow, even though the alternator has the ability to create it, so your ammeter is safe.

This is very scary territory...I'll quit before I step in a big pile of amperes.

Stuart

Clint Lovell,

After a good nights sleep, and a second look at your post, I think Waldo53 diagnosed the problem right off the bat. If you wire it as you have stated, the BATT, or power wire from the alternator will be tied to a common terminal on the starter solenoid along with the main power coming from the battery which starts the rig.

This type of connection is pretty standard...if you use a volt meter in your dash. If you want a true representation of charge/discharge, your alternator output must go through the ammeter on its way to the battery. This connection would be on the same side as any load.

The way you have described it, the alternator would be able to charge the battery without going through the ammeter, which means, as Waldo pointed out, that the meter would never show a charge, only a discharge from the loads (fuse panel). I think this is how it works.

Stuart

Since American Autowire did not show any Ammeter possibilities in their wiring diagram, I called their tech support about my question. I was told that they did not include any info about ammeters because they viewed them as unsafe in a modern setup with large capacity alternators, such as I will be using. They advised to delete or leave uncionnected, the ammeter and to install a volt meter either in its place or elsewhere in the truck. That all sounds great, but does anyone know of a voltmeter I can put in the stock TF dash in place of the ammeter?

Firstly, what an excellent weblink in Tim's (Tclederman) post in this thread -it seems to have everything alternator covered off, those pictures will be worth a thousand words when I need to take my alternator to pieces!

I bought my truck with the ammeter wired, and with the needle stuck right off the end of the "charge" scale -the ammeter was correctly connected, it looks like a previous owner started the truck with a near flat battery.

The solution I am going to try in order to keep the dashboard looking standard and have a working ammeter, is to put 6 or so (low resistance) 50W resistors in parallel with each other but then with the whole parallel array wired across the terminals of the (new) ammeter, this should push 300w or near 28 amps of the charge (or discharge) through the resistor array with the rest going through the ammeter; I'll need to get a near match of resistor array resistance to the resistance of the ammeter to get a reasonable current split.

Has anyone else tried a solution like this before? I can't see any real downside except that it will make the ammeter insensitive to small charge or discharge amounts, also I'll need to put the resistors on a substantial heat sink up behind the dashboard to stop them getting cooked.

Stuart.

just so I understand this.....the correct wiring for Clint would be
battery + to solenoid to ammeter to fusebox to alternator?....or battery + to solenoid to ammeter to alternator and also to fusebox?
I'm asking cuz I have my '59 alternator wired direct to the battery (it isnt a one-wire alternator, has a regulator on the firewall, but I am guessing the concept would be the same)

Carl

Carl,

Your SECOND description is correct. Does it have ammeter in the factory gauges? It will work fine without going through this gauge, you just won't be able to monitor it.

Stuart

Stuart,
I do have an ammeter in the instrument cluster. My ammeter does read because it is wired from the hot lug on the starter to the ammeter. I am working on eliminating all unnecessary wiring and that wire is one that will be gone. I will connect the alternator wire to the ammeter and then to the battery to replace it. After making this change then I only need one wire from the starter to the battery side of ignition switch, right? Sorry for hijacking your thread Clint.

Carl