Ammeter to Voltmeter change

I cut the ends off and wire nutted them together with whatever other leads were on it. convertible, power windows etc..

He's kidding (I HOPE)!

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


The best way is to disconnect the 2 wires from the bulkhead on the engine side and splice properly. This avoids having high flow thru the bulkhead and under the dash.

That's the way I was leaning to. I've heard that if it's done this way you're keeping that current out in the engine compartment and not taking it inside where it's not necessary.

Reply to RodStRace: Thanks for that link. It should be required reading for anyone doing this conversion

you need the power wires inside- if you disconnect them at the bulkhead- you will have no lights, ignition or anything. the power wires that feed the inside are spliced in the harness wires that feed the amp meter!!!

Check out the previous post that has a link in it to a web site. You are 100% correct in what you are saying and I intend to make the changes in my wiring like the link shows.

How it works in the OEM way :
Ammeter needle swings to 'Charge' (C) when the battery is receiving current (from the alternator wire).
Ammeter needle swings to 'Discharge' (D) when the battery is supplying current to the electrical peripherals (the peripherals are all connected to the alt side of the ammeter).
This means all current to the electrical devices (ignition, lamps, windows, radio, which are all powered from the inside) can come from both ammeter wires (the red from the battery, the black from the alt - colors from the Mad Electrical diagram).

Once you have converted the ammeter to a voltmeter, you don't care anymore about the direction of the current flow.
The only thing you care about is voltage : 12.5 or lower : no charging, 13.5 or greater : charging (and 14.5 and greater : Voltage Regulator problems)

But electrical peripherals must still be able to draw current from either the battery or the alternator, as they did in the OEM design.
Think of the battery as a buffer, which supplies power when the alternator can't (when idling, or with the engine off, or when your power consumption exceeds the alternator rating).

What you can do is this :

(1) disconnect the OEM (black) alternator wire at the bulkhead connector, and fabricate a new wire from that cable (with a female spade terminal) to the battery stud on the starter relay.
- Or - disconnect the OEM (black) alternator wire at the alternator output stud, and replace it with a new wire going from the alternator stud to the battery positive terminal [or rather, the battery stud on the starter relay]. Use a proper gauge, at least 6AWG for a 60 amp alt with battery under the hood, bigger for a bigger alt or if battery is in the trunk.
I'd add a 60A fuse in series with that wire (for a 60A alt).
First option may give a more OEM look, especially if you tape the new wire into the headlight harness to hide it.

What this does is reroute the main power consumption of the car (recharging the battery) away from the bulkhead connector and its two tiny, usually corroded, 1/4" terminals.

If you installed a new wire from the alternator stud, you can remove the OEM wire from the harness and remove the corresponding terminal from the engine harness connector, or you can fold it back along the harness and tape it secure, which will leave the alt terminal somewhere safe where it can't cause a short (along the passenger side valve cover).

You then need to connect both red and black cables together on the same ammeter stud (no matter which).

(2) Install relays for the headlights, straight from the battery (starter relay stud again).
Apart from the alt recharging the battery, headlights are the biggest current draw in the car (roughly 8 to 10 amps).
What this does is substract the headlight current draw from the current which has to flow inside the bulkhead through the red wire.
It also virtually eliminates contact wear in the headlight switch, gives more light, etc. That subject alone has been done over and over here.

Your peripherals have power, and the current flowing through the bulkhead connector is just for the ignition, rear lights, turn signals, interior lights and radio.
You don't have to do the headlight relay mod, but it's a nice addition.

Before you do any of this, check your fusible wire (which is in series with the red wire, at the starter relay), it may be worn (corroded under the insulation), and you may break it when you start working around the electrical system. If you can snap it apart with your hand, it's time for a replacement. It's better to have it fail in your garage than on the road at night...

Do you have a good pic of the voltmeter gauge face?
I'm considering this mod myself.

I kept the original ammeter face and in the center it will read 12 volts. I need to check with my cluster restorer as to what higher or lower readings will indicate. They told me but I need to refresh my memory.