"Detail Changes

There were relatively few detail changes during the life of the warbonnet F7s. As noted, many had their original horizontal bar grilles replaced with vertical-slit grilles. In the early 1960s, much of the skirt above the fuel tanks was removed. Also about 1960, all A units were equipped with nose MU, which meant small doors on each side of the upper headlight and MU air hoses on the pilot. When units were equipped with radio, they received antennas on the rear of the roof, often on the centerline. The antennas were most commonly the firecracker or the can style. Five-chime horns replaced the single-tone horns. Switchmen's steps were added to the pilots of many units. About 1960 a grab iron ladder was added to the right side of the noses of A units. About 1969 spark arrestors were added above the exhaust stacks.

In general, a modeler starting with a factory-painted unit will be forced to detail it for its first few years in service, before the horizontal grilles were replaced by vertical Farr Air grilles, which means leaving off nose ladder and MU, leaving the skirts over the fuel tank intact, and using the single-chime air horns.

Service History

The Santa Fe was noted for long stretches of running where speeds over 100 mph were authorized, and it retained an extensive fleet of passenger trains until the late 1960s. As a result, the passenger F7s remained in their intended service longer than equivalent locomotives on many other railroads. Through the 1950s matched A-B-B-A sets were typically seen on the Super Chief, El Capitan, Chief, Grand Canyon, Fast Mail, and San Francisco Chief. A-B-B sets were more common on the Texas Chief, Golden Gates, San Diegans, and other trains. A-B sets could be found on Williams-Phoenix, La Junta-Denver, and Texas trains. Single A units did not normally operate, since the steam generators were needed for both heating and air conditioning, and they were in the B units. However, single A units did rarely operate in combination with steam generator cars. In all cases but the Super Chief (which seemed to keep F3s in any case), the F7s could alternate with PA-1s.

As passenger trains were consolidated and cut in the 1960s, a fifth unit often appeared in many consists of F7s, either as an additional B unit or as an extra A unit in the lead, running elephant style with a second A unit. The additional units were for reliability as well as power, and the extra A unit ran in the front position specifically to allow it to be removed from the point and switched out quickly, with the second A unit available pointing forward right behind it, in case of failure. By the late 1950s all the passenger F7s had been upgraded with nose MU to allow either nose-to-back operation or nose-to-nose, so that it was sometimes possible to see large A-B-B-A-A-B-B-A consists of F7s (and occasionally mixed F7s and PA/B-1s) on power-balancing moves at the head of some passenger trains.
The appearance of the F7s was a point of pride for the Santa Fe through the end of passenger service, and the silver paint on the pilots and running gear of the locomotives was touched up at intermediate stations as part of the servicing process. As a result, some photos show overspray in these areas. However, other than exhaust marks on the roofs, the units were kept very clean.

Units from the 325 class were not needed for passenger service after the 1971 Amtrak takeover. Seven A units were repainted with blue in the areas that had previously been red on the "warbonnet" scheme. These were 325L, 327L, 328L, 332L, 335L, 338L, and 343L. Others were immediately converted to CF7s. As 300 class units came off Amtrak lease, they were renumbered into the 325 class and sometimes received yellow warbonnets at that time. Retirements and CF7 conversions continued through 1974."

Above from ndrr.com