PLEASE SEND HELP RIGHT AWAY BEFORE I SEND THIS FORDS TO THE JUNK PILE.........
I own a 1994 F-150 SLT, 4.9 straight 6, 5 speed manual, all the bells and whistles. It has 141,000 miles and runs great. BUT, I have put 5 alternators on since 1998 when I bought it with 89, 000 miles on it. They seem to last about one year. I usually notice the dash indicator start to jump from charge to discharge. Normally the needle will set about 3/4 on the dial. Never has run at axact nuetral. When I am on a long trip, say more than 2 hours it happens. Before I installed the most recent one I had been using after market alternators (external fan, internal regulator and recifier, 75A). These alternators had the back cover rotated so the regulator set within a couple of inches of the exhaust manifold. The one on there now(broken) is a ford factory rebuild (part number E8PZ-10346-CRM1) and the regulator sets somewhat further from the manifold. I could always smell something hot on long trips before the ford alternator was installed. Evidence proved the the regulator was being melted from the heat on the after market alternators. Since I hadn't smelled anything hot with the ford alternator, I assumed I had it licked. WRONG... Fourteen months (13,000 miles) after the ford alternator was installed, it broke too.
SO, my question is WHAT THE BLEEP is causing my regulator inside the alternator to burn out. There is no evidence of melting on the current one.
Yesterday, I checked the voltage at the battery: engine off: 12.8 VDC, engine on initially: 14.6 VDC abd the dash indicator set normal, after 10 minutes engine on: 11.6 VDC and the dash indicator set 1/4 scale and stayed there. I guess the regulator is bad again. I have replaced battey, positive battery cable, starter, and have checked ground connections. There is no draw on the battery when the trucks sets. I have left it for up to 3 weeks and the truck starts right up.
Someone please help...........

 

Ill check with a friend who has a alternator rebuild plant. I remember him mentioning alot of ford alternators being warrantied and he looked into it and it was caused by something but I cant remember what. I kinda recall something to do with the hot lead running from the alternator.

 

I've got a 94 F150 with a 4.9L. It now has 140k on it, but I have never had any trouble at all with the truck until recently when the alternator went out. I am now on the 7th alternator but only in 6 months - sounds like it is doing the same thing as yours. I installed 3 aftermarket alternators which all burnt up in a matter of days. I finally gave up and took it to a Ford dealership and paid to have it checked out and they have since installed 4 Ford alternators. These have lasted a little longer but after extended trips they are also burning up.

 

Here's what I know now. I took some advise from you on-line folks and went to NAPA. They were knowledgeable and helpful. I asked for a heavy duty alternator for my truck and they carried a 80A and my 75A. The 80A would not fit my mounting bracket, so
I stayed with the 75A. The only difference between my old motorcraft and the one (Beck/Arnley rebuilt motorcraft) NAPA carried, was the alternator plug (not the regulator plug) was hard wired to the alternator. I had to cut my old plug from the harness and splice the new one in. Idiot proof really. What I found out was that Ford recommends replacing that plug every time you change alternators because the old worn plug can cause heat buildup and alternator failure. Beck/Arnley will not honor their lifetime warranty on the rebuild if the plug has not been spliced in.
So I put it on and works good now...... We'll see how long this one lasts. $152.70 at NAPA for part number 186-6221 with a lifetime warranty. I will say that this is the first alternator that I have installed that when I turn on the A/C, the radio, and headlights, the dash indicator drops and then recovers to normal.
I'll cross my fingers and wait.