MFranke

For some years my 88 S4 suffered from intermittent power seat, memory, and mirror functionality. Often it was either all or none working. Strangely, sometimes the actual seat controls would not work, but the memory buttons would work to move the seat. Recently I reseated and, where possible, cleaned all the connectors for the seats, mirrors and memory, and I cleaned all grounds. Everything worked for a while, and I thought problem solved, but then the ghost came again and one morning nothing worked.

I wiggled connections to no avail. I studied the wiring diagrams and started to focus on the seat controller itself. I held down the seat forward button while reaching under the seat to manipulate the controller board. I found I got some power when I pressed on the board in a certain way. I checked the cost of a new controller, and then decided to see if I could repair my existing controller first. I read on these boards that someone experienced bad solder joints on the circuit board.

I pulled the drivers seat and removed the cover for the seat control module on the bottom of the seat (insert a flat blade screwdriver in the tab slots to gently separate the tabs). I inspected the solder points. At a distance they all looked fine. However, when I took a real close look I noticed the centers of the solder points for some of the plugs had a very small dimple around the pin center and faint circular cracks. I jiggled the plugs to see if I could notice any movement on the solder points. I didn't see anything, but still noticed the faint hairline cracks and I figured it wouldn't hurt to refresh the solder points as others have done. Starting with the points associated with the input power (plug #1 IIRC), I used a soldering iron and some extra solder wire to reflow the solder for the connectors. The ones along the top of the board were most suspect, but I wound up doing all of them because it was easy. Reflowing the solder took less than 5 minutes.

I plugged the seat back in, and everything worked and it still works. The memory panel light now illuminates too like it should. It had been so long since the light worked that I forgot it was even supposed to illuminate. All mirrors work too.

I suspect that the circuit board plug solder points see a stress cycle due to harness vibration over time, even though most of the wiring under the seat is fairly well secured. This may cause the hairline cracking within the pin solder points.

Harvey928

Thanks for the heads up. I will have to look at mine shortly.

Gary Knox

Mark,

Great Post!! I've put this in my procedure documents for future use. I have a set of 12 way seats I'm planning to put in the '94, and will do this procedure on the memory module before installation.

THANKS SO MUCH for your experience.

Gary Knox

ROG100

Hi Mark,
I have the same intermittent issue on the GTS driver’s seat. Sometimes memory does not work and the seat switches themselves do not work. Fuses checked for continuity and replaced with new which also check out good.
Once the seat was out the 14 pin was cleaned and checked. Moving the wires would give a good connection sometimes. Following the main cable to the control box in the base of the seat seem to isolate the problem there.
Following your instructions I removed the cover and can see the bad connections and dimples on some of the main joints. All three of the main power plug were looking bad.
Next job is to re-solder the joints so help needed please?

My 25w Radio Shack iron does not cut the mustard or in this case solder.
As an electrically challenged owner please could you recommend a good iron and the correct wattage so I can do this job correctly first time.
Thanks,
Roger

PortlandTom

I had the same problem with my GTS for years. My first observation of the problem was that the seat controls only seemed to work when the clutch pedal was depressed. So I spent hours going through the wiring diagrams to see how the clutch operation could affect the seat motors!

I finally realized that the pressure of my leg on the seat when depressing the clutch must be moving something on the underside of the seat. I then spent many more hours checking all the connections under there.

I finally found a thread a year or two ago describing this exact problem. I resoldered all the connections on the memory controller for the connectors that the harness connects to. Haven't seen the problem since.

Roger, I just used a cheap Radio Shack soldering iron as well. Just touch each solder pad under the row of connectors until the solder melts. Maybe add a little more solder. Should be fine.

Tom D.
'93 GTS 5spd., Amazon Green

ROG100

Tom,
That is my problem - the iron I have will not melt the solder at all, even after leaving it heated for 30 mins.
Have to buy another one so I thought I would ask for a recommendation.
Roger

soontobered84

Roger, I have a Weller. Any Weller is a good one for soldering wires. Doc is gonna hate me for telling you this, though. He has seen the trouble I can get into with my Weller and the instrument panel foil.

As a matter of fact, you can use my Weller if you like. Just let me know.

Dave928S

Roger, I have a Weller 80W with a little bit less than a 1/4" tip, which is a good all round iron with plenty of power to quickly reflow joints. I also have two other irons .. a 12W for fine delicate electronics and an adjustable wattage 15 - 40W. I find that the bigger iron is best for reflows because you can do it quickly, without risking cooking a component, which is more likely with a smaller iron held on a joint for a long time to get it to temperature.

I use the smaller irons for delicate stuff, like foil or board tracks or very heat sensitive components, where you need to work up to just the right heat with no more to spread to other areas.

Choose a fairly small diameter resin cored solder so that you don't flood the joint with too much solder, and 'tin' the iron with fresh solder each time after wiping off the burnt flux and debris on the tip, from flowing each joint.


.... and BTW ... manuals are better than slushboxes.

PortlandTom

Roger,

Looks like you got good advice on soldering irons before I had a chance to respond. I've never been picky about soldering irons, but have generally had good results. I've never done ultra precision work, however. I hate Radio Shack, but it was convenient the last time I needed one.

One thing I would avoid are the so called "cold" soldering irons - the battery pwoered units that are supposed to heat up instantly. I bought one once, and could never get it to work.

Tom D.
'93GTS 5 spd., Amazon Green

928nut

Just put a bit of fresh solder on the soldering iron tip and then place it on the joint you're trying to reflow.. You may find that the iron you have is sufficient after all. A "dry" tip doesn't transfer heat very well.

outbackgeorgia

Roger,
A 25watt iron should work fine, but if the tip is not prepared properly, it will not work.
It needs to be "tinned" by cleaning the tip to bare metal when cold with a file or sandpaper, then when hot, flowing solder on the tip and wiping with a wet rag or sponge.
This should give a tinned look to the tip, not brown oxidation that I suspect you are seeing now.
Then when you touch the tip to the board, the solder should reflow quickly.
Try to practice on an old board of any kind if you have one.
A new iron will work because they are usually ready to go without any oxidation on the tip, but your existing one will be fine.
Dave

SeanR

Rog, bring it over today and we can hit those.

ROG100

Thanks to everyone.

I bought a Weller (25W and $20) and the joints melted easily and flowed as I was expecting. No more problems and both memory and seat functions work everytime.

I have some pictures to post.
1) General picture of circuit board with cover removed
2) Before - you can see the pins protruding through the solder.
3) After
Roger

MFranke

Sorry I'm late to respond. I was busy finally getting around to installing a new fuel pump you'd sent me a little while back.

My iron is a cheap Weller Thermaboost. I'm not sure what the wattage is, but it worked fine on the seat controller boards. Getting some new solder on the tip helps the existing solder to flow, plus I added a slight bit of solder for good measure.

ROG100

.... and BTW ... manuals are better than slushboxes.

Bull****