Whenever I connected the battery on my 78 Eldorado - the interior lights came on, and after about 15-20 seconds they would start flickering and turn off with a strange noise.
It took me a while to find out what was going on, but eventually I could track it down to the illuminated entry system relay.
Sometimes the interior lights would not come on at all, as they should when the car was locked and I pushed the door button from the outside, or the lights would only flicker, and one could hear a relay making a ratcheting sound.
After a while it dawned on me that the illuminated entry relay must be faulty.
After browsing on ebay for months, I found an offer for an NOS relay, which is extremely hard to find and not available anywhere, as this system was an extra cost option in 1978.
After mailing back and forth with the very well informed and nice seller, I began trying to locate the relay in my car to compare it to the one he offered. Two different ones where used in 1978. They came from two different manufactures but were interchangeable. They have different terminal locations which do not matter though, as there were two different connectors used which you can connect to both models. The part number for the relay is #3063206 - it's the same for both models.

It took me a while to figure out where the relay was hiding, as the factory shop manual did not reveal its location.
I finally found it behind the drivers side kick panel. You have to remove quite a few of the interior panels and the door sills to get access to it. Another problem is that the kick panel is connected with the hood release lever and cable, which makes it very difficult to remove. Luckily I could spread it open wide enough to access the relay without removing the hood release cable, which would have been a pain in the butt to get out.
I removed the relay and compared it to the one I found on ebay, and it was identical to the one which was offered. So I hit the "BUY IT NOW" button immediately as I was concerned that somebody else could buy it.

I then opened the relay up. I wanted to take more pictures, but the battery of my phone died, and I had no other camera at hand - thats the reason why I unfortunately do not have more pictures of this repair.

Everything looked good inside, but then I found out why the relay did not work properly.
It should be mounted to the car with a screw which acts as the ground for the relay, which acts as a 20sec timer for the illuminated entry system.
But there was no screw on the relay… After further investigation I found a broken screw underneath the carpet, and the rest of the screw was stuck inside the screw hole.
It looks like the screw already broke off when the car was assembled and nobody cared as it might have worked for a while… Sometimes the system worked and sometimes it didn't… Probably the owners did not even notice the problem - it took me about a year to notice it as well…

I had a hard time getting the broken screw out of the hole, but after fiddling with it for about an hour, I got it loose and could screw it out. Luckily I had a spare screw and reinstalled the original relay with the new screw, and voila - it now works perfectly again. It probably never worked that good before - even when the car was new…
Too bad I had already ordered the new relay - but at least I have a spare NOS part now, which I will hopefully never need!

My original relay after I opened it up

The NOS relay I found on ebay - part # 3063206 - its exactly the same one as I originally have in my car. It is made by Philips.
The NOS relay I found on ebay - part # 3063206 - exactly the same one I originally have in my car. It is made by Philips.

Tags:1978, 1978 Cadillac Eldorado Biarritz, 1978 Cadillac Repair Tip, Relais, Illuminated Entry, 3063206