Amp meter question, 1966 Mustang - Ford Mustang Forum
LinkBack Thread Tools
post #1 of 4 (permalink) Old 03-04-2009 Thread Starter
Biggghiggg's Avatar
Joined: Feb 2009
Location: Fresno
Posts: 8
Amp meter question, 1966 Mustang

The amp meter on my 66 ticks over to the right every second or so. It will be right in the middle and then it ticks to the right. Battery has never went dead but the dash lights flicker when the gauge does. Is this normal for these cars or maybe the alternator is going bad or maybe a wiring problem? Electrical is not my strong replies would be appreciated
Biggghiggg is offline  
Sponsored Links
post #2 of 4 (permalink) Old 03-04-2009
GT Member
Classic Member
5.0L Member
S197 Member
jerry9665's Avatar
Joined: Aug 2008
Location: Norco
Posts: 1,257
Doesn't sound like a big deal. Does the flicker change the idle or vise versa. The alternators in the older stangs were never great you could upgrade to a higher amp unit.

13 Mustang GT 5.0
92 Mustang LX 5.0
65 Mustang Hardtop 289 C.I.D.
jerry9665 is offline  
post #3 of 4 (permalink) Old 03-05-2009
SHELBY GT 350 Member
Classic Member
Ivy66GT's Avatar
Joined: Dec 2008
Location: Albuquerque
Posts: 6,400
Originally Posted by Biggghiggg View Post
Is this normal for these cars or maybe the alternator is going bad or maybe a wiring problem?
Do you mean the standard Mustang ammeter or an add on one? The following assumes you are talking about the the standard ammeter gauge.

No, it is not normal. I would guess an electrical problem since the stock 'ammeters' are pretty useless. They don't tell you much about what the alternator is doing.

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 this 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 a shunt. That allows the meter to use very small wires and saved Henry a few $$. It is an ammeter, but the scale is so huge that the needle will barely ever move. It takes like 230 Amps 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.

If you are seeing the needle and the lights both flicker I would say there is a loose connection or short in your wiring. It likely has nothing to do with the alternator. The reason you don't see the flicker in the other gauges is that they are extremely slow acting and you never see the effect. The ammeter responds quicker and lets you see the problem.

Do the lights flicker by getting brighter or by going dim? If it were a true indication of charging, a needle flick to the right would say more alternator output and the lights should get brighter. If the lights instead get more dim then its almost surely a wiring problem.

If there is actually a charging problem I would suspect the regulator before the alternator. The alternator is pretty simple and dependable although not a very high output. The regulator has a bunch of mechanical switches that can easily burn and not work well.
Ivy66GT is offline  
post #4 of 4 (permalink) Old 03-05-2009
GT Member
66 restomod's Avatar
Joined: Jun 2008
Location: Benicia
Posts: 1,491
Nice write up Ivy66Gt.
The amp meters are really worthless and really just fills a hole in the cluster. A volt meter would have been a better choice of instruments to install, IMHO...
+1 on checking all of the wiring connections

A code 66 coupe, Father~Son Restoration
289 4v, Roller Rockers, Electric fan
Performer & 650 Edelbrock
MSD ignition, Crane Cam
Tri Y into 2.25 Shelby side exhaust
T5 conversion, Hydraulic Clutch and 3.55 Trac Lok
CSRP SN95 Discs
<=== CLICK on the "house" to visit my 66 website!
66 restomod is offline  
Sponsored Links

1966 , alternator , electrical , mustang

Quick Reply

Register Now

In order to be able to post messages on the Ford Mustang Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a VALID email address for yourself, otherwise you will not receive the necessary confirmation email needed to confirm, validate and activate your new AFM member account.

Failure to provide a VALID email address, will result in the cancellation of your new AFM member account registration.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

For the best viewing experience please update your browser to Google Chrome