[mmcginty67]

I was just wondering if anyone else has experience with this issue. I have a 1967 and my alternator gauge really doesn't move much. I checked the voltage with a meter and it is charging, but the gauge does not move.

[jim293]

Welcome to the site. Lets try your question in here.

[Jonk67]

Same here, the needle just sits right of middle towards the 'C'. I switched from a 65A to a 100A and the needle reads the same, just right of middle. I wish I could find an amp gauge that reads to 100, that would tell me something more useful.
Jon

[hypostang]

They really are not supposed to move much , as long as the system is working they should remain somewhat still .
If you want more information or movement try installing a voltage gauge .

[66restomod]

C is for "charge", D is for "discharge" some what in the middle is correct, when high beams are flicked on it should move a little. If it dosnt work at all, an aftermarket gauge it the best, autometer has great choices.

[mmcginty67]

Thanks to all for the response. I was sort of thinking the same thing about the needle being in the middle. I mean that's why the middle is there on all gauges, so you know if it is too high or too low.

[nigel]

Welcome to the site.

[Ivy66GT]

I thought I had a thread on this subject but I can't find it.

The first Mustang ammeters in 65 were wired like you might expect with a big wire carrying current to the ammeter. Starting in 1966 they are wired pretty lame and will rarely give you any useful information.

A real ammeter is wired so that all the charge/discharge current is measured directly. That takes bigger wires than Ford wanted to pay for. If the car is wired as original the ammeter is essentially measuring the voltage across a 2 foot section of 12 ga wire between the alternator and the battery. In EE terms its called an 80:1 shunt. (For every 80A out of the alternator only 1 amp goes through the ammeter.) Full scale meter deflection is with 2.8 A @ 0.64V at the solenoid end of the ammeter wires.

That allows the stock ammeter to use very small wires and saved Henry a few pennies. It is an ammeter, but the scale is so huge that the needle will barely ever move. It takes like 230 Amps (2.8 x 80) to peg the needle in either direction and that is nearly impossible to do unless you have a massive short that you could find more easily with a smoke detector. With the typical 10 or 20 amp charging rate the meter might move about a needle's width. A useful auto ammeter should have a scale of something like +-60 Amp ... NOT 230!

Since so little current goes through the ammeter you don't notice over the years that the connections may corrode and the ammeter gradually won't be reading ANYTHING. That is how it is on my '66 coupe and likely many others out there as well. My recently re-wired convertible does show a small needle movement but you have to be watching closely or you will miss it.

Unfortunately, because of the way the harness is laid out you have to hack and re-wire quite a bit to put a truly useful ammeter on one of these cars. The original ammeter wiring is useless for wiring a REAL ammeter since it would require an ammeter with full scale deflection at less than 1 Amp (60/80 Amp). Even if you had such a meter it could not be accurate since the reading depends upon resistance of the wires in the harness which depends upon temperature.

fuggedaboutit