I have a 2002 F250 Super Duty (Lariat) with the 7.3 power stroke engine. The truck was recently purchased and it looks like the PO installed new batteries not long ago. The alternator looks like its been on the truck for a while and seems to be doing what it should.

That said I wanted to buy a second alternator to swap out and keep the one that's on it as a spare. Picked up a new AC Delco alternator and when I got it home I realized it is only 110amps.

I have the single radiator with two battery setup. I don't push a sound system, however I might want to use a winch at some point down the road.

Will the 110amp be plenty? Is 200amp overkill and could too many amps cause more problems?

 

"Too many amps" isn't really a problem. Current is drawn, not applied. You can monitor and measure the health/voltage of the batteries and, charging system yourself and make a determination on how things are working. So long as everything is working as it should and within spec I would take the new alternator back for a refund, or exchange it for what you want.

 

Not sure what our specs are but definitely replace factory specs

 

Is there a specific way of testing an alternator with a 2-battery setup? The Autozone tester showed a bad alternator, but the batteries are fully charged and have been for weeks (tested last week, still a quick start). The Autozone guy said his tester was only designed to work with single battery vehicles.

 

You have one battery, though in two separate locations.

 

Have him disconnect one battery at a time and test it that way then.

 

Take it back and get the 140 amp alternator for a 2005 Super Duty. You simply need to undo 3 screws to clock the alternator so the connectors are in the right position for your 7.3. I have one on my 7.3 Excursion and it does a MUCH better job than the dinky, stock, 110 amp, small case alternator. The 140 amps is a large case alternator that is better able to handle the demand on these trucks. It's no DC Power 200 amp, but it's a better option.

 

Does that alternator work with the stock belt?

 

Yes it does

 

Did you shim the alternator with washers or grind the mounting bracket to get it to fit? Don't forget that part.

I hit the mounting bracket with a grinder on mine. I'd also recommend using a new, not rebuilt alternator.

 

Couldn't he start the truck and turn everything on (A/C, high beams and high fan) and check the battery voltage to see if his alternator was keeping up?

 

Yes, and it probably will. Especially when new. It's when you start adding aftermarket stuff that puts a bigger strain on the battery, or when you start making a lot of short trips that the lower amps come into play.

 

I need to shim the 140 on my 7.3 with some washers. Its on my list of "Things the 7.3 Needs".

 

You should be fine. I still run the original stock alt and I have winch, off-road lights, HAM radio, scanner ect. and I don't ever have an issue running what I need. It's not like everything is going full tilt all at the same time.