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1968 DeVille Climate Control Issue

Started by Bentley, July 07, 2014, 07:03:30 PM

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Bentley

Hello Everyone,

I'm having some issues with the climate control system on my '68 DeVille, and was wondering if anyone could help. I had the entire system rebuilt 5 years ago, and everything worked fine. The mechanic who rebuilt it specializes in vintage automotive AC, so I trust his expertise. Recently the cold air wasn't blowing out as hard, so I took it back to John the mechanic. He diagnosed it and installed the following parts:

• Rebuilt power servo
• New air inlet kick panel, dual port actuator
• New mode door, single port actuator
• New defrost actuator
• New blower motor

Now he cannot get vacuum to the master switch - so the blower won't turn on. There is good vacuum coming off the engine. And there is good vacuum at the transducer. He jumped the wires and the blower started working normally. Both of us are pointing to the rebuilt power servo as the culprit, but I just wanted to get your feedback or opinions. Thanks in advance for your help.


Wes
Wes Bentley
CLC # 30183

"Cadillac Kid" Greg Surfas 15364

Wes,
The first thing I would suspect would be either a vacuum leak in the control circuit or a non functioning temperature delay valve.  The second is part of the heater water control valve, and that can be checked by removing the two vacuum lines that go into the side of the valve next to each other and connecting them together. If that doesn't get vacuum to the master switch I would suggest checking all the (small) vacuum lines very carefully to be sure they are connected and there are no leaks, especially "frayed" tubing at the connections.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

chrisntam

I can't directly answer your question, but I know someone who can.  Cadillac Tim.  Here's a link to his website:  http://cadillactim.com/page4.html

He has a book specifically on repairing/troubleshooting/diagnosing a/c issues and it is model year specific.  I highly recommend you get a copy of the manual ($45 iirc).  If you need an immediate answer, give him a call!  He is very helpful!

I'm working on my '70 and have his book.  I'm not getting air into the passenger compartment and his book tells me exactly where to look and what to do.  It tells about how to test each component and how to repair some of them.

On the surface (of your mechanic's diagnosis), it appears he's replacing a lot of things.  That (to me) is a little suspect, but I'm not a mechanic.  One thought is of course he'll fix it, he's replacing everything.......

Best of luck on your repair, I'm in the middle of mine too.

chris.
1970 Deville Convertible 
Dallas, Texas

"Cadillac Kid" Greg Surfas 15364

Wes,
Just another thought.  If, when the wires on the master switch are jumped, the system operates correctly, namely the system goes from heating to cooling as you slowly rotate the temperature control valve (with the system and engine on of course) and the correct temperature air comes out of the lower vents on heat and the dash vents on cooling I would not tend to fault the power servo, but again look for a vacuum leak or stoppage in the circuits leading to and from the master switch.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Bentley

Hi Chris and Greg,

Thanks for your help. We are going to check the temperature delay valve and all of the other vacuum lines carefully. And I ordered the repair manual from Cadillac Tim. Thanks again.


Wes
Wes Bentley
CLC # 30183

chrisntam

Do let us know what the issue was.  It's always nice to know the "rest of the story"!
1970 Deville Convertible 
Dallas, Texas

Bentley

Hi Everyone,

I asked this question in an old post and Chris asked me to post again when the issue was finally resolved. Well Chris, you were right. The manual from Cadillac Tim is really what helped us. Turns out the rotary vacuum valve on the rebuilt power servo was incorrect. They rebuilt it with the wrong valve. But they sent us a replacement valve promptly. The next problem was the vacuum switch on the controller. So we replaced that. Also, while the mechanic had the heater cases open to replace the actuator, he also replaced the heater core. Then he charged the system. Now the system works perfectly. Thanks again for all of your help and feel free to email me if you need vendor contact info.

Wes Bentley
wesleybentley@sbcglobal.net
Wes Bentley
CLC # 30183