I experienced low voltage on gage on my 93 F150 4.9L & sure enough killed the battery after a day of driving. Just replaced alternator & this did not solve problem. Checked the alternator harness for continuity & replaced the connector when I changed alternator. I notice that with key on and engine off or running that alternator light does not come on. Took instrument panel apart & checked bulb which is OK. Anybody seen this before? Any help is appreciated.

Thanks

 

I have seen that on some Fords that, when I replaced the Alternator it would not charge. The original plug going into the Alternator had a Green wire with a red stripe in the center of the plug. This worked with the original Alternator. I had to move this wire to the outside (I) position on the new Alternator to get it to charge.

 

Thanks, I think you may be onto something there. I will have to take a look at it in the AM. Do you just swap the green-red(I) with the yellow-white (A)? I am not sure what the order of the 3 connectors is.

 

NO, the Yellow-white stays on the (A), Green-red on (I) and White-black on (S). Some do not have the White-black wire going anywhere and some have it going from (S) to (S). Unless you get the Alternator from Ford it may be wired a little different inside and they all will test good at the auto parts store.

Just make sure that the Yellow-White has full Battery Voltage on it at all times and the Light Green-Red wire is hot with the Ignition Switch in RUN and no voltage on it in OFF.
The White-Black wire will have from 3 to 6 Volts on it while charging, this is called exciter voltage if the wire is used. Some Alternators will have an internal connection and do not need this external wire.

Here are some diagrams of your sysems.

http://www.autozone.com/images/cds/g...3d800a3a60.gif

 

The majority of aftermarket alternators are pure garbage, I wouldn't sell one to Saddam. Please research your alternator at fordfuelinjection.com
If your alternator has an external fan and hooks up via two plastic connectors then it is time to upgrade. research 2nd and third generation alternators. You want the higher output third gen alt, it features and internal fan, smaller pulley and needs to be hard -wired.
I suggest go to a professional starter/alternator shop

DO NOT BUY A LIFETIME ALTERNATOR FROM ANY DISCOUNT NATIONAL AUTO PARTS STORE, I guess NAPA is OK but otherwise see a pro rebuilder.

 

I checked & it was wired just as you stated. Checked the green-red wire for voltage & got nothing (explains the light being out!). Chased the wire down & it turned out to be a break just before the big multi-pin connector on the firewall.

Thanks for all your help subford

Joe