1985 Eldorado remote keyless entry (key fob) help?

[DLMapes]

Hi all,

Second owners of a 1985 Eldorado.  At purchase, the original owner gave us 3 sets of keys for the car, each set with its own remote fob.  I have used one set & remote almost exclusively since purchase 4 years ago with no problems.  Recently, that remote started acting funny, so I figured the batteries were going.  I replaced them with the same (correct) batteries, 2016, but the remote will no longer work.  I took it one step further and changed out the second set of batteries with another new set, same result.  I then checked the other 2 remotes (I put fresh batteries in them also); one remote works fine, one does not (that one I know is a replacement, it has an Olds logo imprinted on it, and no, I'd never tried to use it before, so I don't know if it ever worked or not).

At this point, I'm figuring one of two things - either the primary remote (and the Olds marked remote) have gone bad, or, since it took a few days to get new batteries, and then changing them, programming may have been lost in the set I usually use.

The numbers on the two Cadillac remote cases match - 3165135.  The two remotes with the Cadillac logo are both TRW, with "FCC ID: 6043VT1" and "DOC (Can.) K508" on the back (top), along with 3165135 on the bottom.  The one with the Olds logo has no numbers on the back, just the "how to use" instructions.  I'm going out on a limb and assuming at one time it was programmed to this car, but since I've never used it, I can't swear to it.  Oddly enough, in trying to find replacement key fobs, using the 3165135 number, I keep coming up with results for key fobs fitting 1993 Cadillac Devilles - none for 1985. 

In any case, I'm at a loss, as I can't find any information on reprogramming a "new" remote.  So, my questions are:
1.  Does anyone know if the different year fobs are supposed to work on other vehicles (the ones I have seem to, but I want to make sure before purchase).
2.  If I can find replacement fobs that are "supposed" to work, does anyone know how to reprogram them for our Eldorado?

Thanks in advance!

[fishnjim]

There early GM remotes, and others, had issues with the circuit board contacts.  The carbon "keys" under the silicone pads would not contact after the solder oxidized a bit.  Sometime leaves black marks on it.
What we used to do was take a pencil eraser, and light rub the contact surface to clean.   You have to take apart to do it.   You can wipe with alcohol pad too but don't get it wet.
Beyond that, could need new ones.   Sometimes the coin batteries don't make good contact either, so make sure the little contacts are connected and bent and engaged right and battery in the right way.

[DLMapes]

Good suggestions, thanks.  I've tried the eraser, with no results (these remotes are spotless inside!).  Weird part is I remember when I took the batteries out of the one I usually use, they were 1 positive up, 1 positive down, yet the remote itself says both positives down.  I've been playing with it a bit, but still not working.

[Eric DeVirgilis CLC# 8621]

Keep in mind the problem may lie elsewhere.

The first Cadillac with factory installed keyless entry was in the 1987 Allante. Anything before is aftermarket installation. I believe GM may have supplied a kit for dealer installation but even the quality of these varied and were generally not as reliable as remote systems installed at the factory. May be going down a rabbit hole with no guarantee of success so bear this in mind before throwing money at it. 

[DLMapes]

Thanks Eric, I didn't realize that.  Makes sense now that the numbers I've been using to search for a replacement are coming up as remotes for diferent vehicles.  I still have one remote that does work, so now if I choose to get a second, I just have to find a way to get it programmed to the car - which may be more headache than it's worth.

[D.Smith]

1985?   Has to be aftermarket.  Cadillac didn't offer a factory installed remote keyless entry system on the Eldorados until 1991.

GM had dealer installation kits available made by Code Alarm. 

Can you post a photo of the remotes?

[DLMapes]

Aha!  That's why this remote looked so familiar - I had Code Alarm remote starters/alarms on previous vehicles.  That leads me to thinking...  There is still a Code Alarm dealer/installer not too far away, and there is also a shop nearby that installs aftermarket electronics that I've used for years on all my remote starters/alarm systems on my vehicles.  If I can find the appropriate remote fobs, I may be able to call them to see if anyone can program them to the car.  I also have the pictures, but am not too familiar with posting them, so if they don't show up, I hope someone can talk me through that as well!