97 f150 wont charge

[paulmagee]

hi i have a 97 ford f150 i put a new battery and a new alternator still no charge does anyone have any ideas what might cause the alternator not to put out oh also i have put a second alternator in that was tested to be good for shure i got it to start charging playing with fuses pulling them all then reinserting them however drive the vehicle down the road and it all of a sudden stops charging anyone wanna put there in ?

[94XLT]

i dont no much about these things but maybe a short in a wire or maybe the ground cable on the battery is not grounded to the block.

[way2old]

If you got it to charge by removing and installing the fuses, look at the connections on the fuses. Might be something easy to fix. If the fuse connection is spread, that might be the problem.

[paulmagee]

checked all that cleaned with crc connection cleaner still not resolved

[Selectron]

This is the wiring diagram in the Repair Info section at the Autozone website. If that link doesn't work then try this one. I've found that sometimes when an F150 wiring diagram covers several years and models then they aren't always entirely accurate, so there may be detail differences on the actual vehicle.

Notice that inline 20 amp mini-fuse which feeds into the regulator; if you do have that fuse in your model then you're probably not aware of it since it's fitted inline, so I would look for it and check that it's clean, dry and making good contact.

There are a couple of voltage checks that you can do with the engine and ignition switched off, using either a multimeter or just a 12 volt test lamp. That feed into the regulator via the inline mini-fuse is hot at all times, so you should have battery voltage at that terminal at the alternator, and the diagram is showing the wire as being orange/light blue. Similarly, you should have battery voltage at the alternator output terminal - that's the heavy gauge wire shown as yellow/white which is likely connected to a large threaded stud. If 12 volts isn't available on either of those terminals then start looking for an open circuit in the wiring - it would be a good idea to rattle the wiring harness while you're checking those voltages in case there's an intermittent open-circuit.

The looped wire shown as white/black which feeds out of the regulator and then straight back into the alternator output stage is probably ok, because you've tried two alternators and it's unlikely that both would have a faulty wire or connector.

The voltage regulator (and, in turn, the alternator) is switched on by the voltage which it receives on the light green/red wire from the ignition switch via the charge indicator warning lamp. Provided that the lamp illuminates when you switch the ignition to the Run position, you can assume that voltage is reaching the regulator - if it wasn't then the lamp would have no path to ground so it wouldn't illuminate, and the regulator/alternator wouldn't be switched on either so there would be no output. If the lamp lights though then that section is probably all good.

If your wire colours don't match the diagram, you'll still be able to identify the output terminal because it has the heavy gauge wire attached. Not counting the looped feedback wire, that only leaves two other wires - one of which should have 12 volts at all times, so you should be able to identify the wires that way.

[cam 540]

I had the same problem with my f150 it turned out to be the big plug in the back of the alternator went bad. You can check it by putting an volt meter on the battery and push down on that plug it the volts go up when pushing on that plug that will be the problem and yes any auto part store sells that plug. Hope this helps you!