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This I am quite proud of. I read everything on here about seat memory after doing a search and couldn't find a definite answer to the problem, of a car that refuses to accept new seat memory settings. Several people have posted with this problem, over many years.
Seems to be, it's corrosion of the circuit board in the memory selector switch. It was that on the two such switches in my possession that I tested, anyways, and I fixed them.
I had the problem in one car for all the three years I had it, and in my newly acquired '96. But my other '96 had functioning memory, and would take new settings.
I thought it was a seat controller brain problem, but I took the switch off my car with memory that worked, and tried the two other switches I had and they DIDN'T work in that car. Then I took all three switches to the other car and tried, and the switch from the good car made the memory function work fine in the other car. So I pretty well knew the problem was the switches.
The switches are in the side covers obviously. Pry knobs off seat controls, take out T10 screw below knobs and one straight in from back, and T25 screw under black pry-out cover, then lift side cover up from bottom and drop its top lip out from under seat side upholstery. Unplug the switch - - there's a catch you can pry back with your fingers. And tip in the catch at front or rear of switch and it can be pushed up out of side cover.
They're not easy to pry apart - - three paring knives, one tip at each of the three catches on one side, and it's brittle stiff plastic so they're hard to get in. But you can work them, then pry and pop that side out and the other side comes easy.
The buttons and springs are captive and don't need to come apart anyways. If any food or soda is in there, you can rinse them out and shake dry.
The switching is done by four silicone rubber domes over contacts on the board, with a little metal disc up inside the dome that gets pushed onto the contacts by the button.
I saw clean-ish contacts and clean metal disks and thought nothing could be wrong, then I looked closer, and saw discolored and rippled varnish along the metal traces on the board's surface leading to and from the Memory contact button.
I scraped this off with a blade and found, corrosion but still good trace copper on the outer side of the board, towards door. Scraped it clean.
But on the INNER side of the board, the trace leading back to the common soldering point was corroded, but scraping didn't seem to get down to metal, just bare board. Tested with a VOM and no continuity at all - - nothing there.
This was true on both bad switches. About 3/16" missing on one, about 3/8" on the other. I scraped the green varnish off the good trace on either side of the breaks, exposing a stretch of bare metal.
Then I used the smallest drill bit I had handy, 1/16", though I'd rather have had a finer wire-size bit, to drill holes partly into that bared metal strip at each end of the gap - - right in the middle wouldn't have left much left of the strip to carry current. There's room above the circuit board on either side for wire to sit above the board and not get in the way of the switches.
Then I stripped some multi-strand copper wire, actually a piece of old zip-cord lamp cord, and twisted it tight and made little bridge pieces of wire with L-bends in each end, and got all strands down into my drilled holes, and soldered them into place, making sure to get a good bond onto the printed circuits.
Pared away a little excess solder, cleaned up the contact spots with a pencil eraser, replaced the four silicone domes (alignment pegs drop into holes in board), then popped back together and tested, and both switches work fine.
I wondered at one side being corroded but still intact, and the other side eaten away. I think it's maybe a chemical-electrical thing? One side has one polarity, the other the opposite, and if there's a film of conducting liquid linking them ions tend to move from one to the other, deplating one side.
These cars have been in the northeast all their lives, and a slop of salt slush could very easily land on the switches and drip down in.
posted by 72.87.60...
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