Tackling the climate control system...power servo rebuild?

[CadillacMac]

I'm learning more and more about the amazingly simple, incredibly complicated climate control system!

Because my power servo is having trouble moving the door open and closed when I move the switch, I ran the vacuum straight from the engine for a temporary fix.  Works for heat! But I think whatever holds the air in there is failing.  Do I have to buy a whole new servo unit, or does someone rebuild/sell the parts inside it?  Would a junkyard unit be in any better shape than what I have on my car?

Same question for transducer...apparently I need that too...along with a compressor rebuild...dryer probably...evaporator...maybe I should just stop now...

["Cadillac Kid" Greg Surfas 15364]

What year are you working on? If the power servo goes to and stays at full heat the actuator is good. 
Greg Surfas

[CadillacMac]

1965 Fleetwood.  I basically have the door forced open to let the heat through, but it can't control the door on its own at the normal vacuum level.  I assumed it was because the transducer or servo (or both) were gone.  Thanks for being brave enough to answer and wade into this!

[Scot Minesinger]

To work on these systems you must have a multi-meter and a hand vacuum pump (sold as a solo break bleeder at auto parts stores).

These are inexpensive tools that are useful in many other facets of owning and repairing a Cadillac of the 60's all the way thru the late 80's - early 90's for sure.  You should buy these if you do not have them already.

Then you should also get a shop manual (presume you have that already), and Cadillac Tim's climate control book (Google Cadillac Tim in Iva, SC).  Tim's book is a time saver and it offers experience.  It is very reasonably priced, the time saved in using it will pay for itself the first use.

Once you get your climate control system fixed, immediately repair anything that fails so it is always one thing.  You probably have two or three things.

Replace all vacuum hoses under the hood even if they look OK.  Especially replace the ones that pass thru the fire wall (just a few of them).  The vacuum hoses under dash generally hold up very well, but you may want to snip off a quarter inch of hose on many of them where it stretched and re-attach.

Put a vacuum (using hand held pump you bought) on the servo (or you could use engine vacuum) and see if actuator works.  If t does not it needs to be replaced.  There is also a rotary vacuum valve inside the power servo that may be bad, so get Cadillac Tim's book to test for that.  The steam boat switch (I don't know why they call it that) has four vacuum connections on it and you should check that too, it often fails - fan operates it is probably good.

Cadillac Tim rebuilds all of the parts in your climate control system, so you will not be without parts.

Best of luck!

["Cadillac Kid" Greg Surfas 15364]

Mac,
It is not a question of being brave, it seems to be a willingness as someone who is not in the business of AC repair but experienced in it to provide what seems to be the next logical step in the diagnosis process you as the questioner describe.  I have done  an ac seminar at the last few Grand Nationals, and as a part of that I generated a little "hand-out" describing the basic (albeit generic) Cadillac automatic temperature controls (ATC).  If you PM me and send me your e-mail I will be glad to forward it to you for your perusal.
The control side of your ATC consisting of the sensor string and power amplifier provide a variable 0-10 volt signal to the transducer which in turn allows more or less vacuum to pass through to the programmer. You said you ran the vacuum straight from the engine and the programmer went to full heat.  Is that correct? If so, it might appear that the programmer might be okay, although the multi port control valve on the programmer is still in question.
Your system consists of probably 57 miles of vacuum tubing, and in many cases the connection between the various nipples on devices are sources of leaks, thus rendering the entire system "confused" and basically inoperable.
Go through the "miles" of vacuum tubing verifying each connection and spotting any possible leaks.   
That done I would take a DC voltmeter and with the transducer still connected, check the voltage to it.  It should vary from 0 to `10 volts (with the key on and the system turned to "auto" as you slowly roll the temperature selector dial from 65 to 85 degrees.
Get that far and let us know what you haqve found.
We're with you.
Greg Surfas

[cadillactim]

Here's a link to my manuals. A lot of helpful info not found in a shop manual.

Tim

http://cadillactim.com/page1.html

[CadillacMac]

To work on these systems you must have a multi-meter and a hand vacuum pump (sold as a solo break bleeder at auto parts stores).

These are inexpensive tools that are useful in many other facets of owning and repairing a Cadillac of the 60's all the way thru the late 80's - early 90's for sure.  You should buy these if you do not have them already.

Then you should also get a shop manual (presume you have that already), and Cadillac Tim's climate control book (Google Cadillac Tim in Iva, SC).  Tim's book is a time saver and it offers experience.  It is very reasonably priced, the time saved in using it will pay for itself the first use.

Once you get your climate control system fixed, immediately repair anything that fails so it is always one thing.  You probably have two or three things.

Replace all vacuum hoses under the hood even if they look OK.  Especially replace the ones that pass thru the fire wall (just a few of them).  The vacuum hoses under dash generally hold up very well, but you may want to snip off a quarter inch of hose on many of them where it stretched and re-attach.

Put a vacuum (using hand held pump you bought) on the servo (or you could use engine vacuum) and see if actuator works.  If t does not it needs to be replaced.  There is also a rotary vacuum valve inside the power servo that may be bad, so get Cadillac Tim's book to test for that.  The steam boat switch (I don't know why they call it that) has four vacuum connections on it and you should check that too, it often fails - fan operates it is probably good.

Cadillac Tim rebuilds all of the parts in your climate control system, so you will not be without parts.

Best of luck!

Thanks Scot!  I have the hand pump, that's what showed me there was ZERO vacuum being held in the servo.  All the vacuum hoses under the hood are done.  (even when into the doors to get my locks working again!)  And my shop manual pages with all the hose diagrams are of course sitting in front of me while I work.  So sounds like I'm on the right track!  No offense to Tim, it seems I was just not properly educated, but I thought his books would be for those who don't read the manual or go by the diagrams.  You're saying it's helpful even when you have the original stuff? 

Thanks so much for the detail Greg, you're very kind, and I get more and more inspiration for all my different projects every day I visit! 

PS...I get to mess with the Climate Control whenever something vital hasn't broken in awhile.  But my radiator looks to be leaking and my rear axle too...now I have to get new seals and bearings!  Servo may have to wait, but I'll keep troubleshooting for fun...

[Scot Minesinger]

Tim's books have condensed all of the climate control information into a more user friendly way.  Then there is additional practical experience information also included that is not in the shop manual.  The best part of the book to me is the trouble shooting guide, which lists each possible problem and the steps to take to cure it.  This is the big time saver for me.  I do own three 1970 Cadillacs and have restored each climate control system, however if they suffer a problem, it is way easier to just read the particular problem in Tim's book and begin troubleshooting, rather than relearning the whole thing.  His books are not expensive and a major time saver.  I am still working a demanding day job and have three teenagers, plus keeping up the house, so time is my very most precious commodity.

You don't have to buy the book, but it is recommended.

Plus you can save some shipping as you do need a rebuilt servo anyway.  Check your steam boat switch too, probably OK if fan operates.  Then make sure your dash switch puts out a varying voltage to transducer when temperature dial is changed.  Check transducer to make sure it puts out a varying vacuum signal upon receipt of varying voltage signal (make sure it is well grounded as a good transducer is often diagnosed bad that is not grounded well by mounting - which relies on compression of sound insulation to make it work).  Then you can send all parts in at once for re-building.

A word on your Fleetwood.  That has a wood piece that goes over top of dash temperature controller.  Remove that wood before sending it out to be rebuilt.  It comes off with two screws from back as I remember.

[chrisntam]

+1 for me on Tim's book.



Highly recommended!!