1970s A/C Power Servo -72 CDV

[Ragnar]

Hi All
Can some plz point out for me on a picture where to locate the A/C Power Servo -72 for the CDV. Iam trying to follow the AC troubleshooting guide to the service manuel.
Thx Ragnar

[TJ Hopland]

There are a few servos so I'm not sure which one you are looking for.  I forget what all the terminology is but there is a servo in the box that would be above the passengers feet.  Its got a cover over it so its not normally visible.  This is the main one the electrical control system operates and is basically the main control engine for the whole system.  I believe it directly operates one are door, a vacuum router thing that then operates other stuff, and the blower speed control so its an important one.  One movement if this one basically does everything. 

[Ragnar]

Hi Tj
Thx for reaching out. Maby 1970 was the last year th ac power servo was fitted in the engine bay and that it the following years became a port off the ac controller.
YouTube ac power servo

Iam working on engaging the clutch on the compressor, and are following the shop manual to narrow down why the ac is not operating. Page 100-1

Qutoe:" 1. Preliminary Test
a. .
Place transmission in PARK and start engine.
b. Disconnect vacuum hose from power servo vacuum power unit, and seal hose with thumb. System and power servo should go to full air conditioning.
c. Connect a vacuum hose from vacuum supply line to power servo vacuum power unit. System and power servo should go to full heat. Reinstall vacuum hoses.
d. If system and power servo performed properly in stops b and c, proceed to step 2.
e. If power servo performed properly, but system did not, in steps b and c, proceed to step 5.
f. If power servo and system failed to perform properly, proceed to step g.
g. Check power servo and temperature door for binding or other mechanical interference. If no mechanical interference is found, replace power servo unit."

Is there an other way to give the compressor a signal to make sure it works?

[Big Fins]

Direct power feed.

[Ragnar]

Direct power feed.

Iam not sure what that implies. Can you elaborate plz 

["Cadillac Kid" Greg Surfas 15364]

If you are working on a 64-70, try pressing "UP" on the bottom of the master switch. That is the vacuum switch that has four hose nipples on it and is mounted on the passanger side of the firewall. If all the wiring is correct and connected, the compressor  should start.
Greg Surfas

[Ragnar]

If you are working on a 64-70, try pressing "UP" on the bottom of the master switch. That is the vacuum switch that has four hose nipples on it and is mounted on the passanger side of the firewall. If all the wiring is correct and connected, the compressor  should start.
Greg Surfas

Hi
Its A 1972
Br
Ragnar

["Cadillac Kid" Greg Surfas 15364]

Compressor should run with ac controller set To anything but off and economy or vent

[TJ Hopland]

I'm confused why 70 keeps coming up?   

The issue is you have a (recently?) charged system and the compressor clutch isn't engaging?   

Question for the group, Does a 72 have the 'thermal fuse' or did that come slightly later with the VIR system?  Those generally blow any time a system has been low on charge.

[Big Fins]

Iam not sure what that implies. Can you elaborate plz 

Run a section of wire from the lead going into the front of the compressor (double plug) to the battery positive. Not a permanent connection, just to be able to tell if the clutch energizes and engages the compressor, noted by the compressor main shaft running.

When you remove the plug from the compressor, one side is the hot and the other goes to ground indicated by a black wire terminating right close by. (Been a while since I was into a 72) You want the hot side. There should be an A/C section in your shop manual. If you don't have one, get one. They are invaluable.