The blower motor on my 67 did not come one when I switched on any heating or cooling position. It sometimes comes on in the "ICE" position but not always. After lots of searching I found out that the vacuum master switch does not get enough vacuum to be switched on. When I push the backside of it - everything works as it should. Of course that´s no real solution. Looks like my system will need a good overhaul. Three parts could cause this problem:
The dash switch with its rotary valve from where I can hear a slight hissing noise,
the power servo on the firewall
or the master switch itself - what I doubt.
As I hate when something does not work on my cars I ordered all the parts. I found a good source which sells all these parts rebuilt. Hopefully they will arrive soon as I would like to have this issue resolved before the Cadillac Big Meet. It should not be too much of a hassle to install them when they are here.
The power servo The power servo and master switch
The electrical circuit of the Air Conditioning system of the 1967 Cadillac DeVille in a digram
Here is a video about the Master Switch that a gentleman posted on youtube