The air condition of my Cadillacs always surprise in a negative way. Every spring something new does not work after I wake them up from their winter hibernation.
This time the 67 Eldorado had a new problem which I had to fix.

It suddenly only blew hot air out of the AC outlets. It did not change modes at all. That was a sign of a weak vacuum signal…

I started to inspect all the AC related vacuum lines of the car which checked out fine. Next I did the test I´m describing here in an older posting, as I suspected that the power servo had a problem.
I soon found out that still not enough vacuum was supplied through the transducer.

That meant that either the transducer could be faulty, the temperature sensor could be defective, or the dash control head would not work properly. I took out the temperature sensor of my 67 Deville to test it in the Eldorado but it did not change anything.

I then removed the control head and tested it with a spare one I once bought cheaply on ebay. It did miss some connectors and switches, it had some blemishes on the chrome and did not look good enough to install it into any of my cars. When I put it into the Eldorado anyway the AC suddenly worked perfectly again.
So I removed all the electrical parts from this working unit and transferred it to the perfectly looking but defective control head. After I had swapped all the usable parts I put the unit back into the car and I now have a perfectly working unit once again.
It looks like that there was a problem in the amplifier part which translates the signal coming from the rheostat into a current going to the transducer which regulates the vacuum going to the control head and the power servo.
Lets see what issue comes up next spring…

The Rheostat when set to the lowest temperature setting shows around 2,5 Ω You can check if it is working with an Ohmmeter.edge
At the highest temperature setting the resistance is getting lower.edge
The Amplifier part of the control head is on the underside. Something in here must have gone bad on my control head. I will try to find out what went bad and repair it to have a spare part.
The 67 Eldorado is back on the road for the 2015 season.



I woke up the 58 Eldorado Seville from its winter hibernation and when I went through all the switches and options I noticed that the front of the seat would neither move up nor down. The motor was running but it did not move. I could see that the front adjuster with the solenoid would not engage.

First I suspected that the switch has a problem - so I took it apart. With a test light you can easily test its function. With a three way jumper wire you can simulate the switch as well at the switch connector. You can see the picture below from the shop manual and its described which terminals you have to connect together to get the desired movement. The shop manual is extremely helpful in diagnosing any seat related problem. Check it out below!

Everything was fine at the switch. So I checked the wires going to the solenoids. There is a plug underneath the switch and I checked the wires from there. Everything was ok there as well.
For some reason the mechanism still did not engage. The front actuator was repaired by the previous owner once, as there were some screws in there which originally were not used. I tightened them and suddenly it worked again when I almost wanted to give up and wanted to try to find a good used one from one of the Cadillac parts places.
I hope it will work now for a long time. The seat is fully adjustable again.

Below are some pictures from the shop manual which should be very helpful if you have power seat problems as well.

Six-way power seat diagram.
Thats the front actuator and solenoid which had a problem on my car. The mechanism did not engage for some unknown reason. Probably a bad internal contact or the mechanism was stuck somehow.
This 3 way jumper wire is very helpful to test the various functions and to rule out any problem with the switch.
The procedure to test all the functions of the seat.
The 6 way power seat wiring diagram.
How to test the circuits.
Front Seat Adjuster Actuator Assembly (1957 and 1958)