1965 Coupe DeVille Air Conditioning trouble shooting help

[Joedaddy]

Hi from Joe Dady

I just purchased a 1965 Coupe DeVille from the original owner. Garage kept Florida car.  The body is near perfect, looks like new.  Very well care for over the years no doubt.  There are some minor defects I can deal with however the AC is not working.  Questions, is there a repair manual out there?  Or Does anyone know of someone who can repair this type of system in the Orlando or Tampa Bay area of Florida?  Any help would be greatly appreciated.
TKX
J. Dady

[The Tassie Devil(le)]

G'day Joe,

Welcome to Cadillac ownership.

The first thing you must do is buy yourself a Christmas Present, in the form of a Factory Shop Manual.   These Manuals will show you everything you need to know about everything within your precious vehicle.   Not sure if GM made a Body Service Manual for these years, as I know the previous manuals held everything within the two covers.   
There are many around, like:
https://www.ebay.com/itm/1965-CADILLAC-SHOP-MANUAL/153763032459?hash=item23ccfdad8b:g:hVIAAOSwhiJd9m5n
and
https://www.ebay.com/itm/1965-Cadillac-Service-Manual-Service-Managers-copy-GREAT-Collectors-Item/123870897043?hash=item1cd747e393:g:cmkAAOSwl0pdT39t

Don't bother with the Digital form, as they are so hard to look at when doing work on your car, as a lot of times, there is backward and forward page flipping involved.   Plus, reading a proper printed book is so calming.

Bruce.

[cadillacmike68]

The second thing to get is Cadillac Tim's Climate Control book for your year. It distills the shop manual into English, particularly with regard to the control head, power serve, master switch and vacuum lines.

[35-709]

By all means.  Get that 1965 Cadillac shop manual, invaluable!  And get Cadillac Tim's book for your year.  Ask around and look for an AC shop that has been around for a while --- I have a great one here in Vero Beach.

Cadillac Tim --- Tim Groves.  Call him at 864-348-7732, leave a message if you get his machine, he will return your call.

[Joedaddy]

Grrrreat Thanks

["Cadillac Kid" Greg Surfas 15364]

Joe,
Do you intend to do the diagnosis and repairs yourself? If so does anything on the AC/heating system work?
Greg Surfas

[Joedaddy]

Greg.  I,m sure some of the parts are working.  I have not checked them out yet.  Ill be needing the manuals that were recommended first.  f I can find someone who knows how to restore the system Id rather do that.  The compressor clutch does not work so right out of the gate Ill be going for a new compressor.

["Cadillac Kid" Greg Surfas 15364]

Joe,
The factory service Manual contains a quite comprehensive section on the Automatic Temperature Control (ATC) system for your car.  It includes a description of all the components and their functions as well as diagnostic Matrices to help isolate the issues.
The ATC system actually consists of 6 distinct and separate systems.  The heating system, the cooling  (refrigeration) system, the air movement system and the air diversion  (dampers and ducts) system.
All these systems are used in harmony by the control system to provide the comfort conditions you, the driver select by your input at the control head (mode selection and temperature dial).
When you break the ATC down to its systems and diagnose each one separately it becomes clear where your "problems" are and how to correct them.  These are relatively simple systems and it you take it one step at a time, learn the components, learn the systems and learn how they operate together you will avoid a costly and inefficient game of throwing parts at the ATC.
Greg Surfas

[35-709]

The AC compressor clutch not working does not necessarily mean you need a "new" compressor.  The clutch engages or disengages by electric current, if it is not getting that current, it won't engage --- just turning the system on doesn't make the compressor engage unless and until some other system requirements are met.  You can test the clutch engagement by hooking 12v to one terminal at the compressor and grounding the other, not necessary for the car to be running.  Even if the clutch assembly is bad, you still don't have to replace the whole compressor, the clutch assembly can be replaced by itself without losing the "freon" charge, if any.
Point is (as Greg has said), don't go throwing parts at it (and making assumptions) until you know and understand what is wrong first! 

[Joedaddy]

Thanks everyone for your help.  Once I get the manuals I keep you posted.

[chrisntam]

What I'll add is this, which may have been explained, but not really sure.

I think the '65 system is relatively close to how the system operates in my '70.

The compressor (and a/c cooling) operates all the time.  It does not cycle on and off.  You want to make sure the a/c system (compressor/clutch, valves, condenser, a/c charge (Freon) and evap core) is working.

You also want to make sure the heating system (radiator, heater core, heater control valve) is working properly.

When you adjust the temperature, a blend door introduces heated air to the a/c cooled air which is then carried inside the car at the requested temperature.

So to recap, make sure the a/c and heat systems are working first.  Then move on to the automatic temperature control (ATC) system (if needed) that sends the cooled / heated air to where it needs to go.  There are sensors in the car that help with directing the conditioned air, dependent on temps inside and outside.  The entire system is controlled by a combination of vacuum and electrical.

The Factory Service Manual will explain all of this.  Tim's book just addressed the ATC system.  I highly recommend his book as well as the FSM.

I suggest you join the local Cadillac club, the members may be able to steer you to capable mechanics to work on you car.  Unfortunately, quality garages that service your car are somewhat rare.

Oh, and welcome.  Please post pics of the car when you can, we'd love to see it!

chris.

[bctexas]

Hi Joe and welcome!  I also recently purchased '65 CDV with non-working AC.  I have a shop manual and Tim's book.  I have worked through the diagnosis that Tim outlines in his most excellent book.  I now have a very good idea which components work and which need replacing.  There is a company an hour or so from me called "Old Air".  A friend has a '64 Dodge with factory AC, and Old Air was able to replace the refrigeration components under the hood of his car with modern parts, and leave the control systems and the interior components untouched.  The system works great.  I am hoping to do the same with my Caddy.  Old Air lists a modern compressor that is a direct bolt-in replacement for the original, so I believe no brackets need be replaced or fabricated.  Anyway, please keep us in the loop on your progress - I plan to restart this part of my car's refurb project in the spring, and would be most interested in seeing what direction you go!

Happy Motoring!

[35-709]

I can also recommend Old Air.

[Joedaddy]

And I'm Back!   First, thank you all for your comments to my post.  They put me on the right path.  I did receive the shop manual and have been using it to troubleshoot the comfort control system.  I have not gotten Tim's book yet.  Looks like that was a mistake putting it off.  Not having it has put me back several weeks.  I am working on getting it now. 

So far:

The master switch was not closing.  My De-Ville came with a spare Servo.  I swapped it out and got the switch to activate but I have no air flow from the AC outlets.  I suspect the vacuum valve on the swapped out Servo.  When I activated the master switch the circuit to the master switch would overheat.  I noticed that the plug to the master switch had been damaged by excessive heat in the past.  I disconnected the blower motor and circuit did not overheat.

The Compressor is not coming on.  I know the clutch is good because when I touched a test light to the master switch power feed to check for power the resistance from the light activated the compressor.  This happens only when the master switch is not active.  Also when the master switch is engaged the test light does not come on, same with the Servo circuit.  I know there is power to it because the blower motor comes on.

I did a ohms test on the three resistors with a multimeter and they seem to be working okay.

I did a vacuum check and have 13 Hg in all positions except off that properly goes to zero.

I checked and have power to and from the compressor switch.

The Hot Water Control Valve had been removed and bypassed so hot water is flowing to the Heater Core.

Again Thanks.
Joe Dady

["Cadillac Kid" Greg Surfas 15364]

Joe,

Without going into a long speil, it does seem that someone has "modified" your system.  Integral with the hot water heater valve is a thermal switch that opens to allow vacuum through the vacuum circuit of the valve when the water temperature is warm.  There should be two vacuum lines that go to the valve, and without the valve in the circuit, the two lines should be connected together
That said your issue with the maser switch is quite common as they really can't handle all the current (for the fan and the compressor) for too ling without failing. They were originally cheap but now are rare as the proverbial hen's teeth.  I have a couple of NOS Master switches that will probably be part of my estate .LOL.
Since you have the FSM I would suggest you take and follow both the electrical and the vacuum diagrams to be sure all your components are installed and connect4d correctly.  Bad electrical connections or leaking vacuum lines will essentially render these systems inoperable.
Greg Surfas

[Joedaddy]

Those to vacuum lines are plugged.  I'll connect them tomorrow and see if it makes a difference.  I got the compressor working today.  It was a simple fix I had over looked.  Bad Ground.  Can't get the AC to come out of the AC vents. I checked for vacuum and have 14 Hg to the mode diaphragm?  I thinking something is not right with either the amplifier or the transducer?  When I get Tim's book that I ordered today it should tell me how to test them.

Joe Dady

[cadillacmike68]

I had a bad ground for the compressor once. Vexed me and a shop.

The master switch controls ONLY the blower fan, Not the compressor. The compressor is turned on by the VENT switch in the control unit( the one in my 68 is bad ) How much fan is via the power servo and/or the LO-AUTO switch and/or the HI-FOG-ICE switch. These switches (all on the dash control unit) route the fan voltage through all, some, or none of the resistors that regulate fan speed. However if it does not get the required level of vacuum you get NO blower fan at all.

The transducer and amplifier control the power servo and tell the power servo how much to pull or let out that long lever. That lever is also connected to the rotary dial inside the power servo to further regulators and control blend doors, etc.

But it is all connected via vacuum!

[TheHomeTownAir]

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