Today I finally found the time to permanently fix the power seat back locks in the 74 Coupe DeVille. The lock on the passenger side always had a little contact problem since I got the car and only worked sometimes… A guy who wanted to help me and who boasted that he could repair everything, tried to repair it last fall but after his “fix“ it only worked for a day and then the locking system was completely dead, after he had worked on it for hours the day before… Now I did what I should have done before - I fixed it all by myself again…

I found a way to remove the seat back lock mechanism without disassembling the whole front seat and replaced the mechanism with one which I got from my favorite Cadillac Parts vendor - Arizona Vintage Parts. As always they delivered a perfect part and it only took me half an hour to remove the old part and install the new one.

The function of this lock is that it latches the seat backs in place when the doors are closed. The lock disengages and unlatches when the door is opened, so that rear passengers can simply fold the seat backs away when entering or leaving the car, without having to push a button.You can hear this "Automatic Seat Back Release" working when you open or close each door.

After removing the plastic covers around the seats - it will look like this. The seat back lock mechanism is hiding inside under the seat back.
You have to remove the lower 3 hog rings to get access to the two mounting screws.

The new mechanism I got from AVP on the left and the old original one which does no longer work


After installing the new part all you need to do is to install the hog rings again and install the seat cover surround moldings. Here I´m using a hog ring plier - but you can use some simple other pliers as well.

DEFECTIVE POWER ANTENNA

I also had to replace the defective power antenna of the 74. The original one had a burnt motor and also the gears and the whole mechanisms were broken. I can´t imagine how this could have happened. When the antenna died it also burnt the fuse. After inspecting the power antenna I decided that it was not rebuildable and ordered a rebuilt one from Arizona Vintage Parts as well.
The antenna can be removed very easily on the 74 - so much easier than on my 60s cars. I was able to switch it out within 10 minutes. It works perfectly now.
It´s very important to me that all things on a Cadillac do work like they should.

This is how the disassembled original power antenna looked like when taken apart - you can clearly see that the motor was burnt.

This is how the disassembled original power antenna looked like when taken apart - you can clearly see that the motor was burnt. Also the mechanism itself was damaged.

The 74 has a working power antenna again.

Tags:Power Antenna, 1974 Cadillac Coupe DeVille, Seat Back Locks, Restoration, Automatic Seat Back Release, 1974 Cadillac Repair Tip, Arizona Vintage Parts

The 1974 Coupe deVille is equipped with automatic seat back release locks.
They are actuated by big solenoids which are mounted in the back rest of each front seat.
When you open the door they are actuated, and the seat backs can be folded forwards to allow access to the backseats without having to manually unlock the seat. You can hear this "Automatic Seat Back Release" working when you open or close the according door.

It worked perfectly on the passenger side, and most of the time on the driver side.
When the door was open though you could sometimes hear a rattling sound from the solenoid as it did not make good contact.

That was not acceptable for my standards of course.
You have to remove most of the back seat material to get to the solenoid unfortunately.

Once we got it out, we took the solenoid apart. Some of the actuators insulation foam had crumbled inside the end stop of the solenoid - so we replaced that, cleaned and lubricated everything, and put it back together.
Unfortunately the problem was still there after this.
So we eventually found out that the striker where the seat latches, was not adjusted correctly. Something must have gone wrong at the factory already.
We had to modify it slightly to make it perfect again, so that the solenoid could disengage itself properly when the seat back was in the back position.

When everything was back together it worked for a while before it broke again. I will have to find a good working solenoid now and replace it once again.

UPDATE: You can read about the final repair here!

You have to remove the seat back material to be able to access the solenoid and latch mechanism

The latch mechanism

The solenoid disassembled - before cleaning - there are two coils inside.

A quick drawing of how the system works.

Tags:1974 Cadillac Coupe DeVille, Seat Back Locks, 1974 Cadillac Repair Tip, Automatic Seat Back Release, Restoration

I´m fully detailing the 78 Biarritz at the moment. During this I think I found the only non working gadget this car offers. The 78 Biarritz came with an automatic seat back release. When you open the door a solenoid engages and you can fold the seat back without pushing any button or lever to allow rear passengers to get in or out of the car. When you close the door again the seat lock engages and the seat back stays in position.

I also have the same system on my 1971 Lincoln Mark III where I had some problems as well in the past with a loose wire.

On the Biarritz the passenger side worked flawlessly, but on the drivers side the solenoid would not engage.
I started my search for the problem at the top of the two door jamb switches which is the one controlling this function.
When I wiggled it and pulled it out, I could hear the solenoid engage. So I knew that the problem must be with this switch.

Unfortunately it's not easily accessible. As I do not have the 1978 shop manual yet - it took me a while to figure out how to access it.
I managed to get to it through the lower dash and to uninstall it.
As it turned out it was slightly bent and did not make good contact once the door was opened.
I carefully bent it back straight - and after some trial and error it was back in working order.
It took me a good hour to fix this.

Now I´m back to cleaning the car to my standards, something that will probably take the whole winter...

The upper switch is controlling the seat back solenoid. (Picture was taken before cleaning the door jambs...)


The removed door jamb switch. When the door is closed no contact is made and the solenoids are not energized causing the seat back to be locked in position.
You can see that the switch was slightly bent - making no good contact.


When the door is open contact should be made and the solenoid should energize... The switch did no longer make a good contact though.


I had to remove the lower dash to access the cables on the rear of the door jamb switch through a tiny hole and disconnect the connector with a long nose plier...


I´m now in the long process of thoroughly cleaning the engine bay to look like new again...

Tags:Door Jamb Switch, 1978 Cadillac Repair Tip, Restoration, Automatic Seat Back Release, Solenoid, 1978, Cadillac, Eldorado, Biarritz