We have a 2002 F250 with 7.3L, 4wd, 66k miles. Our alternator would only work if you reved the engine a few times and then it would kick on (per the gauge on the dash). We bought a reman Motorcraft alternator at our local Ford dealership. It didn't work at all. We went back to the dealership and they exchanged it for another. We installed it and it is doing the same thing our original alternator was doing.

Any ideas or suggestions on what to do next?

 

Take the alt and get it tested or put a real voltmeter on the output. The dash gauge isn't super accurate if you can even call it that. Then start looking at the wiring - alt should be putting out voltage all the time even @ idle. Also make sure the belt's not slipping - the fact that rev'g it up fixes it points to this as well.

 

The gauge only shows voltage in the system not charging, Ask me how I know. You have a bad ground or short somewhere if I was to guess. Let us know what you find please. Chet

 

Chet, yes, the gauge only indicates voltage, but a lower-than-normal indication on the gauge indicates something's not right. A "normal" reading should indicate somewhere around 14.4 to 14.7 volts. Of course, the gauge doesn't read-out directly in volts, but it's a good relative measurement.

A good idea is to put a small (1/4") "triangle" of some-color tape on the instrument panel plastic that points to "normal" when you're sitting normally in the seat and driving down the road. A quick glance will tell if things are "normal" with the charging system or not.

If it's reading 14.4+ volts, you're charging.

The small plug on the Ford 6G alternators is semi-famous for failing. As a result, the plugs are available separately for splicing into place.
http://store.alternatorparts.com/wir...sories-30.aspx

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Thanks for all the input!! We really appreciate it.

Here is what we did:

I went to Advance Auto and bought a Remy alternator that was new, not refurbished. Installed it and it worked for a few minutes then stopped. I took it to Advance and it tested good.

We checked all the wires and plugs, every thing was good.

We put the reman Motorcraft back on it. Still have to rev the engine for it to work.

One of our Motorcraft batteries tested bad. We took both of those batteries out and put the Autozone batteries that were in the Excursion when we bought it.

After installing those batteries, the alternator worked fine. I guess it was just the bad battery.

We bought 2 new Motorcraft batteries and installed them. The alternator has been working fine. I never would have guess it was the batteries with all the different results from the alternators.

Thanks again for all the info! I will let you know if we have any more problems with the charging system.

 

Thanks for closing the "loop" on this, and adding to the experience bank.

Your input may directly point someone else to a resolution of their problem.

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