Today I managed to solve the issue with the partly non working Automatic Climate Control of my 1967 Eldorado. As described in the entries below, the blower would only come on in full heat modes when the car was accelerating. The AC of the Eldorado is very similar to the one from the DeVille btw.
I suspected a vacuum leak somewhere in the system. Troubleshooting began with going through all the vacuum hoses. I replaced some which were a little worn out at the connectors. I also cut off the ends of most hoses, as they were all becoming a little loose during the last 40 years. I then plugged them in again.
Not much did change though.
When I came to the hose of the hot water valve and the delay relay, I had the first success. At least the blower motor would stay on in all “Auto” modes, even when the car was idling - but would still go off in “Fog” and “Ice”. I then suspected a leak in the power servo or in the dash controller. So I installed the power servo from my 67 DeVille where everything works perfectly, to be able to rule out any problems. Nothing changed though - the blower would still come on and off depending on the throttle position.

I then soon found the culprit of the whole issue - it was the master vacuum switch - which seems to have a problem with the internal electric switch. As I had a spare one around I installed it - and voilá - everything worked as it should. It always looked good when I checked it before.
I´m very happy that everything is back in working order. The only thing which I still have to repair is the fast idle diaphragm which completely dried out and is no longer functioning. Fortunately I do have a spare 429 engine in the garage from where I can grab and use this part - so I will repair it soon.
I then need a new condenser which is already on the way across the Atlantic coming from Old Auto Air.
By the way - Cadillactim has an excellent trouble shooting guide for the ACC on his website.

The best troubleshooting guide for 1967 and 1968 Cadillac´s Automatic Climate Control Systems I got today from Gary Sisk - owner of a 1968 Cadillac.
This is a very easy to follow explanation which will save you a lot of time and you do not even need any special tools.
It was written by Lynn Nicholls and can be found on Stampies Cadillac page - here is the direct link to it.

Below you can find some pictures of my system:

I discovered the first issue at the hot water valve

the hoses around the time relay delay were leaking a little bit

for testing purposes I hung a spare master vacuum switch into the car - this solved the problem

the old fast idle diaphragm was leaking and brittle and was replaced with a better one...

the 1967 Cadillac Automatic Climate Control Vacuum Schematic from the shop manual -
1968 is almost identical BTW... Click on the image for a larger view!

Tags:AC, Blower, 1967, Eldorado, Restoration, Troubleshooting, 1968, ACC, Vacuum hoses, Vaccum diagram, Vacuum Schematic, shop manual

Today another 1967 Cadillac turn signal switch arrived for my 67 Deville which is in the shop at the moment with a broken switch. I found a nice NOS switch on ebay and finally it's the correct one. All the ones I bought in the past were the wrong ones as 3 different ones were available in the 1967 models! Non of them is still in production or reproduced and they are very hard to come by. Originally they were built by AC-Delco and Boyne and they are very different as I learned later... I already spent quite a sum for wrong NOS switches. Used ones are usually sold for $250.- to $300.- at the big Cadillac parts specialists... Here is a picture of the NOS one I found - it was manufactured by Boyne.

UPDATE 2010: In the meantime (since 2009) the Boyne switches they are getting reproduced and show up on ebay all the time. Also OPGI shows them in their Cadillac catalog. Its harder to find one for a T&T column as they are not getting reproduced so far. I do not know where one could find a switch for T&T though. If you know of any resource for T&T switches please let me know, I would love to have a spare one for my Eldorado!

When I was looking for a switch for my 1967 Deville, I only investigated resources for cars without T&T columns and this is what I found out:

According to the 1971 parts manual there are two different ones for standard column cars and one for T & T

• 1967 - 1968 (Exc. T & T) Part # 7800483 - Switch, w/wiring harness (Delco-Remy)
• 1967 - 1968 (Exc. T & T) Part # 7805675 - Switch, w/wiring harness (Boyne Products)
• 1967 - 1968 (T &T) Part # 7805676 - Switch, w/wiring harness (Hazard warning switch an integral part)

The two different standard column switches can be identified without removal as the parts manual describes:
„Hazard warning switch is an integral part. Switches can be identified before disassembly as follows: The Delco Remy switch has a square hole for the hazard warning switch in the cover, the Boyne Products switch has a round hole for the hazard warning switch in the cover.“

The problem with the switch on my standard column DeVille was that the return cancel cam broke, and that non of the repair kits were available for the Boyne switch.

Replacing this switch in the steering column is quite a pain - below you can find the instructions from the shop manual on how to do it.

click on each picture for a larger view!


the connections going to the directional signal switch - the turn signal switch connector

If you need instructions for a tilt and telescope column click here for the instructions!

Tags:Restoration, 1967, 1968, Deville, Turn Signal Switch, Diagram, Eldorado, Part Number, Steering Column, How to