Greg, that is an excellent piece of new information!! Thank you

 

The contactor materials are brass and copper, and that's not what you see coming out of the plastic on the outboard side......
Mine is too covered with solder to tell now, but best I can recollect there is a short 1/4" piece of strip that's butted to the ends of the copper / brass strips at one end, and then goes to the connector strip at the other end.... I'm talking like putting your finger tips together tip to tip butt - joint..... I know this sounds crazy, and I thought the same thing you're probably thinking...... Why didn't they just carry the connector strips thru to the connector strip junction point.....
Can you see if yours looks like copper / brass coming out?
I know neither of us wants to sacrifice a good fixed TPS, but now you're making me wonder if I'm not crazy or blind, and I'd like to grind the plastic off yet another one to see if what I recollect is true.....
John, I gotta go, but will check in tonight to see if you've figured out whether I'm losing my mind.....
Best,

 

Unfortunately, mine is back on the car and working, so I don't think I'll use it for forensics. Someone has a bad one that needs to be taken apart. It would be great to know for sure.

 

The tabs that imerge from the plastic on my switch were/are totally covered in solder so I can't confirm the change of material. Springy contacts like those are uisually made from phosphor bronze I think...

Don't worry, I'm crazy and blind as well

 

Greg & John:

I've got this thread bookmarked!

So, Greg, am I correct that the area I circled in red is where you found a broken joint, and the other areas I maked in blue are other butt joints that are suspect, especially the ones on the WOT side that John found broken?

 

Hello JP, John, Bill,

The verdict is in, and I have the pics to prove it...... The contactor strips are one piece thru the plastic with an "L" bend at the end that is soldered to the connector strip...... I apologize for the confusion fellas, but at least now we know...... The problem is cold solder joints at Bill's blue circles only......

Yeah, I thought that there was a poor joint at the red circle, but as you can see, I left nothing to chance and soldered the thing up pretty good across the perceived butt joint, and at the connector strip junction also......
This was on my mind a lot today, so when I got home tonight I decided one TPS must die so that others may live, and I just had to get to the bottom of this..... I took a knife and scraped off the solder on the strips and then eventually yanked the strips out to be double sure..... I believe this was the first one I fixed and subsequently replaced with a new one.... I can see on it why I had mistakenly believed they were butted together strips under the plastic...... You see, I had barely burr-bit-ed to the edge of the hole in the thinner strip when I was grinding the top plastic, making it look as if there was a joint...... John, as it turns out, I'm not crazy or completely blind...... just plain ol' regular dumb.......
One picture shows the thick stationary strip and the aforementioned hole that I thought was a joint on the thinner strip, and the other picture is not so good, but shows both of the strips......
So JP, and John, you guys can rest easy knowing yours are fixed and it is a mystery no more...... And Bill, my bet is still on yours having flaky solder joints.... (blue circles only...)
Best,

 

OK Greg, thanks for that !

There's a hell of a lot of water got into that switch, I've seen several like that.

But the GTS one I took apart was extremely well sealed, which explains why I had to saw the top case half off. I guess they improved at least that aspect of the design.

Here in the UK a new switch (trade price from Bosch dealer) is 80USD..... hopefully we can refurbish some faulty ones in future as long as they haven't had too much water inside.

 

Excellent work, Greg! No doubt this will help a lot of folks.

 

Yes, thanks to all of you guys for working through this issue! I will be one to benefit from your work, as a recent diagnostic session revealed a WOT switch problem on mine. I'll dive in for the repair soon.

It sounds like it might be better (i.e. a more durable fix) to repair the WOT than buy a new switch, no? I have no idea when mine failed; do they last ten or fifteen years, or fewer? It would be nice not to ever have to worry about it again, anyway.

Did I read your post correctly John, that you saw no other signs of wear on the switch, such as pitting at the contact heads? Was that true for you, too, Greg?

Again, TONS of thanks to everyone (esp. John, Greg, JP)!!

 

Chaad-

The biggest issue is if your repaired switch fails again, you have to pull the intake again to get at it.

 

Yeah, Andrew, that's what I thinking about!

 

Very interesting thread. Kudos to Greg for diving into the switch.

I made one of the comments in the other thread about WOT activation. I've been looking for a protractor on and off since you posted this thread. I haven't been able to find one so I had to use the Mark I eyeball.

I just tested a new-out-of-the-box 3-pin WOT switch. On the input side the switch has about 90 degress of rotation from just off the idle-switch to mechanical stop. The switch I have activated the WOT circuit at about 45 degrees of rotation. This is the earliest WOT activation I have seen. I assume that my eye is accurate to 10 degrees at best, so that would put activation at 40 to 50 degrees of rotation at the input.

My black box testing shows that there's significant variation switch-to-switch. I haven't yet flayed a switch so that I can with my own eyes what does what.

 

[QUOTE=chaadster]It sounds like it might be better (i.e. a more durable fix) to repair the WOT than buy a new switch, no? I have no idea when mine failed; do they last ten or fifteen years, or fewer? It would be nice not to ever have to worry about it again, anyway.

Did I read your post correctly John, that you saw no other signs of wear on the switch, such as pitting at the contact heads? Was that true for you, too, Greg?
QUOTE]

Hello Chaad
There doesn't appear to be pitting on the WOT contacts. There is a suppression capacitior across those contacts, as reported previously, which should help in this respect.

The problem is going to be how to be sure any soldered repair to those joints is going to be any more successful than Mr. Bosch's attempt..... but it would last 10 years or so ?

A harder solder with less or no lead could be stronger, but maybe more brittle ?
We need a metalagist's opinion on this...

 

Hi Dave
I just tried two new switches I have here and they seem nearer to 60 deg.

 

Greg: Thanks for the final clarification on where to look for bad solder joints. As I mentioned, I've seen very late or no WOT activation on a number of cars. This is a nasty problem if you drive the car hard, but not a big deal for cruising like most people do. I'm not sure when I'll get the intake off, but I will report back what I find then.