Running a F3 Santa Fe unit only...?

 Santa Fe F A-Units didn't have steam generators, they were in located in the B-Units only.  The only way Santa Fe could run a single F-Unit would've been if there was a steam generator car in the consist.

The  Santa Fe "Super C" (hotshot piggy-back train) occasionally ran with a single F-Unit:

Rusty

Sure they did, that was the whole purpose behind the F unit system, you could run just the A unit, or AA, AB, ABA, ABBA ect.  Google search the Chicago Great Western RR, they would hook up a gaggle of F units to pull grain trains.  They were known for thier "wall" of F units on trains.  So running a single A unit is just fine.     Mike

Santa Fe is a special case.  Without a steam generator in the A-Unit, they needed either a steam generator equipped B-Unit or a steam generator car with a passenger train.  Most of the time it was a B-Unit.

Freight is another matter.  Santa Fe also equipped several 200-class freight A-Units with footboards to use them singally in local service.  Not very popular with the crews because of poor rearward visibility and awkward operating when in reverse.

Santa Fe was also know to run a gaggle of F-Units in a freight train, plus it wasn't unusual for the Super Chief/El Capitan to had 5-6 F-Units on the point.  Also as I recall, the Aberdeen and Rockfish only had a single F3, but that has nothing to do with the OP's question.

Rusty

Rusty is spot on about the steam generators.

Some of the Santa Fe's E units (A) had steam generators so that is why you might see a short Santa Fe passenger train with a single E unit.  Thinking of an E8m leading a train in Colorado on the "Joint Line".

But when it came to F3s, if in passenger service, there would have been a B unit or a steam generator car. 

The steam generator cars (converted from baggage cars) came toward the end of Santa Fe passenger service...late 1960s.  Mainly so the Santa Fe could use F45s and other locos without steam generator run through piping to pull passenger trains, as well as to place the generator cars on the rear for very long train consists. 

There also were the few surplus tender steam generator conversions done during the war years to mate with freight FTs in troop train service.  But these were painted in the freight scheme.

Couple of questions about this topic:

Going through old photographs you can find all kinds of combinations and configurations of motive power. I saw a photo recently, maybe on this forum, of two A units back to back, two A units elephant style and two B's with another A all hooked up and ready to roll. Did a railroad, Santa Fe for example, run two A's back to back with the B unit trailing? I know as model railroaders, lots of folks like to have the "prettiest" combination and not necessarily what often was the real thing. Not complaining, don't see anything wrong in that at all.

Second question is along the same lines. Plenty of photos exist of some diesel powered passenger train with quite a few head end cars - mail and fast freight, I assume. How did they transfer all the necessary power through the head end stuff to the passenger portion of the train, or was the power car located between the head end cars and the passenger cars?

Thanks.

and besides.... it's your railroad, you can run whatever you want

Highly unlikely, at least not in any photo in any of my Santa Fe books.

Typically, Santa Fe ran A-B-B, A-B-B-A, A-A(elephant-style)-B-B-A, even A-B-A-B-B-A mu combinations on their passenger trains.

Rusty

Not a very common or glamorous assignment, but I have seen single ATSF F's on weed spraying trains.