I just got one from a Cougar restoration site. He also has Mustang amp meters he converts to voltmeters. I am pleased with mine.

Rocketman's Classic Cougar Innovations

 

Yep, I ran into the same problem. So I went with a set of custom gauges in the original cluster.

 

Rocketman's Classic Cougar Innovations

I bought one from this guy. 110% satisfied with the product. Very easy to install.

You can thank me latter!!

 

Same as ScottsGT, used Autometer in my stock gauge bezel. Very clean and much better gauges.

 

I'm not sure, but will the Cougar gauges work in a '66 cluster? I know the face is shaped different and the needle is white and not orange. But that's an easy fix.

 

I think I remember seeing a post somewhere recently about converting to stock gauge. Try looking for that. If this is an option, it would be my first choice. I can't seem to find what I remember seeing.

If that Cougar gauge would work, it looks like a nice option.

 

The main issue with the 65-66 cluster is depth. In 67 Ford completely changed the ammeter design from an open framed fairly flat gauge to a deeper metal case.
The problem is that the 67+ ammeters are too thick to fit into the pre-67 clusters.

 

Here Mustang Monthly talks about having a company called Auto Instruments rework it.

Ford Mustang Instrument Panel Troubleshooting - Mustang Monthly

http://www.autoinstruments.com/

 

I just came across this info.

The attached JPG shows how the ammeter wiring in a factory 1966 harness works. I have only drawn the wires involved in the ammeter circuit and given their colors and size/length where appropriate. The red and yellow wires go through a connector in the firewall which I have not shown to keep the drawing somewhat simple. The lengths given for those wires includes the wire on both sides of the firewall.

The ammeter is actually reading the voltage across what I drew as the big purple wire in the drawing. (Its actually a black/yellow wire but that's hard to draw.

) The little rectangle shown in the middle of the yellow wire by the solenoid is a connector built into the wiring harness. These wires are all wrapped together inside the underhood harness so you have to scratch your head a little while to figure out where these all are and how they connect. The 4-way wire connection down by the alternator is a thick lump you can feel inside the taped harness, its not anything you can actually see without removing some tape.

The ammeter coil itself is about 1/6 Ohm but when you include the red and yellow wires to and from the purple wire the total impedance for current flow through the ammeter wiring is right at 1/4 Ohm. I give example numbers for an alternator charging 100 Amps into the battery. About 1 1/4 A, or 1/80 of that charge current will go through the wires to the ammeter if all the connections are good. Unfortunately, full scale deflection of the ammeter takes about 2.8 A so that means the charge rate at the upper end of the ammeter scale is almost 230 A. Neither 230 or even 100 A will ever happen with the stock alternators which explains why this meter needle never moves a whole lot even if it does move.

On many cars, the connection at the solenoid end of the red and yellow wires are dirty or broken and there will be NOTHING going through the ammeter. That doesn't hurt anything else in the car so few ever take the time to figure out there is even a problem with the wiring.

Electrically this is called an 80:1 shunt circuit. Enjoy.

 

I made this post just a week or so ago: http://forums.vintage-mustang.com/vintage-mustang-forum/659627-ammeter-voltmeter-conversion.html.

Since I took the photo, I have blacked out the brand name at the top of the gauge.

 

I'm running the stock bezel- but with aftermarket gauges (one of the reasons I went that route was to get a voltmeter vs the ammeter)...

Right now I have AutoMeter gauges, but I wish I could find an aftermarket set of gauges that pivots from the TOP like the factory gauges. With the way the bezel sits it is difficult to read gauges that pivot from the bottom (because the brow of the gauge cluster bezel obscures the top of the gauge from the driver's position).

Anyone know of a top pivoting aftermarket gauge?

 

Thanks everyone... Candoo - I emailed Rocketman Classic Cougar... it looks like he has a solution. Good one!

 

One thing often overlooked, but was briefly mentioned earlier, is the slightest corrosion on connectors can render the AMP indicator inoperative.

Using Brasso™, Q-Tips™, and a toothbrush, clean all of the connector pins and sockets at the firewall, alternator, and solenoid, apply a light coating of dialectric grease, and reassemble. Often a "dead" AMP indicator will suddenly come back to full function.