1970 DeVille Conv A/C question

[Raymond Humphrey]

Im new to the club (no number yet) and new to working on cars.  I am hoping to get some help.  My air conditioner is channeling all the A/C to the floor vents, it starts coming out the dash vents but within a minute or two it dumps to the floor vents.  I donnt know where to begin twouble shooting... any thoughts?
Thanks,
Ray

[Brett]

I am no expert, but in my 71 two separate problems were fixed by replacing the climate control head and the programmer..both on separate occasions. The whole system in my 71 is vacuum operated and you need a vacuum guage to check the operation...I didnt do this since I had spare parts to swap in and check the operation.

[TJ H 20664]

Where the air comes out is controled by doors in the ducts that are actuated with vacuum motors.  The vacuum motors are controled my either the control head (the part with the lever and dial on it) or the programer (seperate control box somewhere under the dash).   In  my 73 manual it looks like they both have vacuum controls on them and they interconnect. These systems are far to complex to just go probing around blind but with the book are not that bad. The factory shop manuals have very good details on these systems, if you plan to do any work at all on this car yourself it will be well worth the money to get one.  They are on ebay all the time, typical cost around $30.  Dont waste your money on anything other than a GM shop manual either orignal or a reprint.  The haynes and motor books cover too many models and years to be of much help.

Here is one on ebay right now:

http://cgi.ebay.com/ebaymotors/1970-Cadillac-Eldorado-Deville-Service-Shop-Manual_W0QQcmdZViewItemQQcategoryZ34212QQihZ010QQitemZ200071446643QQrdZ1QQsspagenameZWDVW TARGET=_blank>http://cgi.ebay.com/ebaymotors/1970-Cadillac-Eldorado-Deville-Service-Shop-Manual_W0QQcmdZViewItemQQcateg

TJ H 20664

[Raymond Humphrey]

Brett,
Thanks for the info.  I now have a place to start.  My system is also vacume controlled and I have replave the vacume lines and checked the vacuum in the system.
Thanks again.

[Raymond Humphrey]

TJH,
Thanks for your explanation of the head, I didnt know what that was called.  I have a shop manual and now that I know what to research, I can begin.
Thanks,
Ray

[Barry M. Wheeler #2189]

Hi, I just had the same problem with my 79 Brougham. Blew cold all the time. I changed the head, and finally got a used programmer out of a recently running wreck from a Cleveland junk yard. Took a round trip to Indy yesterday and was warm as toast. Finding a programmer for the earlier cars might be difficult, but I would think that GM(Cadillac) would use the same item as long as they used the body, which is usual practice. So, check a Master Parts Book. The only one I have to hand is a 71, so naturally, that is all that fits. I have a later one upstairs that will list all the 71-76, that Ill check tomorrow. If you could get one out of a 75 or 76, there would be more chance it was still good. What is maddening about this is that I have access to a large box of early take-out Olds C body MANUAL controls that would do away with the vacuum if one could figure out how to hook them up. Over the coming years, that might have to be an option, authentic or not, as working programmers give out. I wrote a note to remind myself to look it up in the AM.

[bill henry]

check the operation of the power servo under the hood on the top of the firewall

[Barry M. Wheeler #2189]

I checked, and my newest MPB was from 76-79, with a programmer number of Group 9.275 Part # 1223605 fitting C D E X bodies. The 71 # I had was the same Group/ #7930135. Along about this time, they changed the numbering completely. If you go this route, make sure that the air horn has a piece of masking tape/cardboard over the bottom opening. This should be referred to in the Shop Manual. This is the ambient temperature sensor assy, I believe. One of my new programmers did not have this tape/cardboard and the installers didnt notice it when they installed it, and found it didnt work, either. Good luck. This whole assembly can be a pain to fix.

[Barry M. Wheeler #2189]

I guess it would help if I checked the year of your car... I looked at my 71 manual, and cant make heads or tails out of the assembly before the ones Im more familiar with. Sorry. Try Lars Kneller, in LaPorte, IN. He is familiar with the 66 and possibly could help.

[bill henry]

the power servo controls which vents the air comes out it is vacuum controlled so make sure it has vacuum  no leaks and is moving to the proper position.  a factoery shop manual would be a great help

[Raymond Humphrey]

Thanks, perhaps I will be able to work on it this weekend.

[Raymond Humphrey]

Thanks for all you ideas and help.  Ill try Lars if the servo is not the issue or if the manual doesnt help.

[tim groves]

Sounds like you have a vacuum leak, which is not letting your vacuum actuator operate properly.  The vacuum is enough at first to operate the actuator (sending air flow out of vents), but then bleeds off, sending air flow back to the floor.  I have a troubleshooting guide on my website http://www.cadillactim.com TARGET=_blank>www.cadillactim.com
Check it out and look under Tech Help where you can download the 1969-70 Climate Control Troubleshooting file.  Tim