I have to take apart and clean the various components of my S-Type key fob at least every six months because it suddenly decides to quit working. Sometimes I can get it to work again by using my wife's now-rarely-used S-Type key fob while holding my S-Type key fob right next to it. But as of yesterday morning, my key fob is very confused. When I press the unlock button, it locks the car. When I press the lock button, nothing happens. When I press the trunk open button, the trunk opens normally....

Any ideas on what is causing this confusion?

My wife's S-Type key fob continues to function properly. It stays tucked away in her pocketbook so it remains nice and clean with no grit or grime getting inside the case. I think that has a lot to do with my fob problem since I hike six miles most early weekday mornings (my keys are in my shorts pocket and after my six-mile hike I'm completely soaked through with sweat and look like I've just emerged from a swimming pool)....

 

Could the battery be failing? I get similar things with a TV remote and it's fixed by swapping its batteries.

 

Anything is possible, but I've swapped batteries in my fob before to no avail. Cleaning the innards is what has restored its function in the past. Previous to this issue, it either worked properly or it didn't, no confusion between the buttons....

 

I also bend out the battery contact tabs when I clean it which helps. I assume you are using electronic component cleaner.

 

Your assumption is correct....

 

Sounds like a stuck button to me. Check the operation of each button microswitch once disassembled.

 

It seems strange but my 2005 key fob works great and I have never changed batteries in the almost 5 years I have owned the car.
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Update:

I took the fob apart to clean it as I always do. As I removed the circuit board from its case, the tiny black 8-pronged chip fell off the board onto my kitchen table. Obviously, its solder points had gotten weak over the years and were causing the button confusion....

I gathered up all the parts and took them to Key Harbor at the local mega-mall. They replace the microswitches in these key fobs all day every day. But they cannot re-solder this tiny 8-pronged chip back onto my circuit board because they do not have a solder tip that small nor the magnifying equipment to allow them to see work that small. They offered to order me a new circuit board for about $160....

So I went to a high-end stereo shop that does in-house board-level repairs. No can do. Same reason - no solder tip small enough....

Went to yet another high-end stereo shop. No solder tip small enough there, either....


Any recommendations, guys? Surely someone has the proper equipment to solder this chip back onto the board. I admit - the chip is tiny. Less than one-quarter the size of a typical woman's small fingernail....

The other issue is that I do not know which way the chip orients on the board. It is symmetrical like a spider, so it could fit either of two ways....

Man, I hate these key fobs....

 

You can figure the direction by comparing with your other fob.

Probably they're wave (flow) soldered. Potentially you (well, someone determined) CAN resolder it. People do this with 64-pin and 100-pin chips etc!

Such as Geoff's Projects - Surface Mount is Easy

Now I don't say YOU should do it but a good hobbyist might well.

Thing is that people like remotes and want them small and light plus batteries to last a long time. Well, a tough ask and roughly state of the art when the redesign S-Type came out.

 

Look carefully at the circuit board and see if the solder pads are still intact. I am suspicious that the copper based pads have eaten away from the moist/salt environment you mentioned. That may be why no one can easily repair it.

 

JagV8 and WhiteXKR,

Thanks for your input....

The solder pads are still intact. With the chip off the board, I took the opportunity to carefully clean the entire board with electrical contact cleaner and Q-Tips. It's sparkling clean now, and the pads are clearly visible. The downside is that they aren't much larger than the point of a small sewing needle....

I cannot see any markings on the loose chip to help with orientation regardless of whether it is compared to my wife's fob. Maybe some markings are there that can only be seen with the proper magnifying equipment....

My wife has suggested that I call a jewelry repair shop that she has had very good experiences with. Jewelers and watch repairers indeed do some extremely micro-soldering. Whether they are willing to solder a chip back onto a circuit board remains to be seen. I'm going to phone them once she locates their phone number....

 

If the pads are actually intact, PM me and I will offer to solder it back for you for shipping costs.

Of course, I cannot guarantee this will solve the problem, since electronic damage could have occured as the part fell off. Also, in rare cases when a parts develops an internal short it gets so hot that it unsolders itself.

By the way, these parts are 20 year old technology: they are HUGE by today's standards (look inside an Iphone). I do not know what those service guys were talking about.

 

Ahem. I was carefully not mentioning today's sizes!

 

Hmmm...perhaps you are right...talking about size is never a good idea.

 

WhiteXKR,

Thanks so much for your very generous offer to give this a shot. PM sent....

 

Jon, I was going to suggest trying to contact George (Androulikis) but I see WhiteXKR has you covered.

Jolly good show, White.

Good luck, and post back how it sorts out.

 

Will do. Sure hope WhiteXKR can work his magic here. I really don't want to shell out $160 for a new circuit board....

These key fobs will no longer be in my shorts pocket when I hike. I always drive my Ram pickup to the park for my early morning hikes, and from now on I will take only my simple Ram key with me. My two Jaguar key fobs will stay safely at home....

 

A simple option to protect your FOBs from perspiration or other H2O is to enclose it in a small sealable plastic sandwich bag, squeeze out all the air, then seal the bag before stuffing in your pocket.

 

One other option...

I got 2 brand new fobs from eBay for $50, gave one to my indie as payment for programming, got the other one back a few hours later, perfect!

 

Update:

Steve (WhiteXKR) is truly a wizard. He resoldered the loose chip back onto the key fob board, found some other suspect solder points on the board that I had not noticed before I mailed it to him, and resoldered those weak points as well. It is amazing how perfect his solder points are. They put the factory solder points to shame....

Not only does my S-Type key fob work perfectly each and every time now, but its operating range has increased at least three-fold....

Many thanks to Steve for his considerable prowess with these circuit boards. He has inspired me to take much better care of my key fobs going forward....