Why different a/c controls on a '70 Deville & '70 Eldorado?

[chrisntam]

I've been reading up on the a/c controls for my '70 DeVille, some of which are different than on a '70 Eldo.

The control head (in dash) appears the same, but there are different under hood switches/controls and possibly different sensors/controls under the dash.

For those that are familiar with both systems:

1) Any ideas why the eldo was engineered differently than the DeVille?
2) Are there any benefits (driver/passenger) of the eldo system over the DeVille?

Seems to me the end result of conditioned air in the passenger compartment would be the same.

Thanks in advance for sharing your expertise on these systems.

["Cadillac Kid" Greg Surfas 15364]

Chris
During the “early” years of ATC (1964-1970) there were constant changes in the systems as the technology developed in parallel with the commercial AC industry. 1969 and 1970 saw some of these changes incorporated in the RWD cars that were not in the Eldo.  My best guess would be that they were going to the 2nd generation Eldo in 1971 and since some of the 1970 RWD AC changes were “experimental and yet unproven they did not want tore took too drastically for the 70 Eldo.
It turns out that both RWD nod Eldo systems changed for 71 and were virtually identical for the remainder of the “full size” run
Greg Surfas 

[67_Eldo]

Yes to what Greg said plus:

The DeVille was a Fisher C-body car while the Eldorado/Toronado/Riviera was an E-body car. These platforms were developed at two very different times and served different needs.

So I'm sure the new wing-window-less ventilation systems used on the E-body cars, in addition to the differences between C- and E-body cowl shapes, required a number of design changes.

[cadillacmike68]

The differences are because 1969 and 1970 ElDorados Still used the vacuum actuated fan relay via the Master Switch, AKA "Steamboat" switch" with all of its sensitivity to vacuum leaks, etc.

In a similar fashion, the 1969 ElDorado used the newer vacuum actuated cruise control, while the 1969 RWDs still used the large electric and mechanical linked system used in 1968.

It was most likely a way to use up excess parts of the old master switch arrangement, because the newer system was much simplified over the 1964-68 steamboat switch dependent system.