My 94 F150 XLT SuperCab 4.9L, 5 speed manual has 138,390 miles on it. I bought it 4 yrs ago with 89K miles already on it. Since that time I have put 4 alternators on it. At over $200 a piece, I have had enough. I constantly have a hot elecritcal smell in the cab. The ammeter shows normal but far to the right until about 15 minutes after driving. I have an after market Sony CD palyer that was already installed before I bought it.
Seems to go through an alternator per year. Dealer service department says they have no idea what the problem is. They suggested disconnecting all the chassis ground wires and checking for corrosion. I have done some troubleshooting. Good grounds and continuity from battey to chassis to starter. Oh, I have replaced the starter & solenoid, battery, and positive cable from battery to starter. When engine is just started, I have 14.7 volts from battery to chassis and Ammeter needle sits on the L of normal. It takes about 45 minutes to get the hot electrical smell. Ammeter needle is then at M. The needle never goes to the left of center on the gauge.
I don't have any stereo amps that would draw excessive current.

Does anybody else have similar problems or maybe a solution to mine?

 

14.7 seems a bit high?

If you smell it in the cab, have you carefully looked under the dash? How bout the wiring for the blower motor? All fusible links?

 

I have the same specs. on my truck, but have not had any alternator problems in 125,000 miles (knock on wood). A few years ago, the corner of the fuse block that holds the blower motor fan melted though. Check that. I just pulled the wires out the back of the block, soldered them together with an inline fuse holder and haven't had any more problems.

Rob

 

My '92 has needed two alternators in 105K miles. I got them for $89 at a NAPA, so I don't understand your $200 cost. But that is besides the point...

You may have some sort of short in your system that is taxing the alternator.

Anyway, to diagnose, disconnect the (-) battery cable; connect the red lead to the removed cable, and the black lead to the (-) battery post. Set the meter to the highest AMPs scale first, or let it autorange. Don't turn on any big elecrical loads, so you don't burn up your meter. Close the doors & trunk so the lights aren't on.

BTW when you first connect it, it might show some current for maybe a minute, for the interior light delay relay or the alarm or something... Otherwise, the only loads will be the dashboard clock & the stereo's memory; & they're really tiny.

If you see a draw registered on the meter, you have a short somewhere.

It could be the alternator itself. To check this, remove the wiring plug from the back of the alternator. If the meter no longer registers any amps, then the alternator is internally failing and needs to be replaced.

If the meter still shows AMPS being drawn, then reconnect the alternator wiring plug, and remove each fuse in turn until you find the circuit with the short, then trace it down from there.

 

The reason for the $200 for each alt is because like he said it's a XLT! That's all the acessories, power everything so he would need to have a high amp alt..I think it's 140 or something and the regualy $80 one is like 90amps.

 

After closer examination, my 4.9L has a 75W alternator. This this inadequate due to all the bells and whistles that come on the XLT. I called the dealer and they comfirmed that the 75W is the only listed alternator for my truck. Could this be why I keep burning out alternators?

 

I doubt if the 75amp alternator rating is the problem. If you smell something burning, there is a short somewhere. It is very, very abnormal to have a burning smell, or to burn out four alternators. If the 75 amp alternator was the original equipment on the truck, then it is the correct one to use. Getting a more powerful alternator wouldn't matter.

Since the only non-original part on the truck is the aftermarket CD player, I'd start by removing it entirely and see if the burning smell still exists. The person who installed it might have used the wrong power source for it or screwed up the wiring so something is shorting and frying.

 

75..what???? I have an eddie bauer(same as XLT)...power everything and it requires I think 140amps...I called Auto zone and they said my 96 requires a 90amp or a 140amp. The 90 wouldn't be enough for all the accessories...Dude you should call a auto parts store or something because most dealers are brain dead anyways.