Automotive Air Conditioning Information Forum (Archives)

69Eric on Mon January 03, 2011 10:11 AM

Year: 1969
Make: Cadillac
Model: DeVille
Engine Size: 500
Refrigerant Type: N/A
Ambient Temp: N/A
Pressure Low: N/A
Pressure High: N/A
Country of Origin: United States

I recently picked up a 1969 Cadillac Coupe DeVille, I knew this car would need some TLC but being a mechanic I traded my 99 Civic for it. I however have never had this particular problem with any car before so I am asking for your help. The blower does work in the car but the air is blowing out of the air inlet vents which are the vents on the outside of the car on top of the firewall and no air at all is blowing out of the cabin vents. At the moment all I am trying to do is get heat in the car because obviously right now that is all I need and I will worry about purchasing a compressor later for AC. Any and all help will be greatly appreciated. Thank you

Dougflas on Mon January 03, 2011 12:29 PM

Vacuum lines are usually causing this type of problem. With no vacuum, the blend doors revert to defrost.

69Eric on Mon January 03, 2011 12:35 PM

I have a lot of vacuum lines that are not attached or not where they need to be because of the previous owner doing a engine swap. Do you know of any websites I could find free vacuum diagrams? Chilton does not offer a manual for this car

Dougflas on Mon January 03, 2011 3:56 PM

will check and see if I have anything for a 69

Dougflas on Mon January 03, 2011 5:29 PM

have info. send me email address to: dktv at aol dot com in subject put caddy and I'll send you vacuum info


You should look on ebay for a programmer to test the system. Robinair made them. Last I saw, they were going cheap.

Edited: Mon January 03, 2011 at 6:21 PM by Dougflas

Dougflas on Mon January 03, 2011 6:23 PM

In order to get heat, vacuum must be applied to the heater control valve. Diagram says it all

69Eric on Mon January 03, 2011 10:28 PM

Thank you very much. I just emailed you

newton5 on Wed January 05, 2011 3:53 PM

You said the air is blowing from the inlets?
Look to see if the blower motor has been replaced at some point, then verify the proper direction of rotation.
I've seen quite a few aftermarket blower motors that were wired improperly (reversed polarity) and turned the wrong direction.

NickD on Fri January 07, 2011 5:08 AM

Those were the days when you found a coupon in the back of the owners manual to send in a check for four bucks and have a complete shop manual sent to you postpaid. This car should have the automatic climate control, recall laughing as it was a one transistor circuit. But gosh my memory is getting bad, but do recall the entire climate control and programmer could be removed and set on your workbench to test out all the functions and see what was going on. Think the vacuum mode switch was motor driven, that one transistor controlled a blend door motor for temperature control. Was a lot easier to work on these new microcontroller systems. Does yours have that red blue temperature controller potentiometer?

Could try doing a google search for a shop manual. Use to have a stack of these old manuals, but for personal problems, had to get rid of all of them. Closest cars I had to yours was a 70 Buick Rivera and a 73 Cadillac Fleetwood, had problems with both systems, like getting baked out, recall pulling both systems, cleaning all the switches and lubing them, even taking apart that vacuum switch with screws on it. But that was a long time ago.

With that 70 Buick, got Canadian headgaskets, they didn't sell high octane gas in Canada, were thicker to reduce the compression down to 8.5:1, put in an HEI distributor, it fit perfectly, a 10SI alternator to get rid of that troublesome electrical mechanical regulator, and an intake manifold with a carburetor and EGR valve on it when you could buy something like that from a wrecking yard for ten bucks and take it out yourself. That way I could burn the new lead free gas, actually still got close to 22 mpg with that car. Leaded high octane gas shot up to $1.55 per gallon, where unleaded was more like 60 cents a gallon. People back then using unleaded gas in these cars didn't go very far with large holes burnt in their exhaust valves and pistons. This all started with the newly formed EPA. Said we only had eight years of gas left, that was like 40 years ago, then all these new SUV's only getting around 7 mpg around town, I quit. Cars are pretty much useless without gas, AC wasn't a problem back then, is now. Everything is a problem.

NickD on Fri January 07, 2011 5:11 AM

Sure your engine is a 500 CID? Memory tells me the DeVille had a 472, only the Eldorado came with the 500.