Rear Top Sensor pictures

[DanF]

After having 2 sensors replaced at the dealer to get my top working again I decided to take one apart. The following pictures are of the top sensor, this little thing cause major top and trunk failures. How it works explained here: Potentiometer - Wikipedia, the free encyclopedia

Part Number

There are 3 Sensors

Small Plastic Shaft the drives the internals, half round, half flat.

The inside

This where it happens, small plastic shaft rotates the internal electrical positioner sending a signal to the computer tell it where the top is.
As you can see all the components are small and delicate.

 

[onalaska]

Thanks for the close up pictures to see what is actually in a sensor.

Potentiometer likened to the rotary volume control of radios from the 1940's through 1960's. Stone age technology in today's era of robotics with rotary shaft encoders, optical encoders and hall effect devices, etc. If you remember back in the day, radios would develop a "noisy" volume control which would produce a lot of static when turning the volume up or down. This "noise" is due to the wear of the contacts and resistive material from use and noise being produced by the sliding contacts when positioning something as critical as the top components on the XLR would result in a real problem. We used to use contact cleaner to help clean and lubricate the contacts and reduce the static and it sometime worked and sometime the potentiometer was just too worn out to be fixed by cleaning. These sensors are so small and probably sealed so I doubt you could get any spray cleaner in there to do any good, but if you could it may temporary fix the problem and could be a tool to isolate the defective sensor for those without a Tech-2.

 

[Phrede]

Thanks for the close up pictures to see what is actually in a sensor.

Potentiometer likened to the rotary volume control of radios from the 1940's through 1960's. Stone age technology in today's era of robotics with rotary shaft encoders, optical encoders and hall effect devices, etc. If you remember back in the day, radios would develop a "noisy" volume control which would produce a lot of static when turning the volume up or down. This "noise" is due to the wear of the contacts and resistive material from use and noise being produced by the sliding contacts when positioning something as critical as the top components on the XLR would result in a real problem. We used to use contact cleaner to help clean and lubricate the contacts and reduce the static and it sometime worked and sometime the potentiometer was just too worn out to be fixed by cleaning. These sensors are so small and probably sealed so I doubt you could get any spray cleaner in there to do any good, but if you could it may temporary fix the problem and could be a tool to isolate the defective sensor for those without a Tech-2.

I agree. Ancient technology on a technically advanced vehicle. Somewhat disappointing. The slide-wire potentiometer was invented by Johann Christian Poggendorff in 1841 and Thomas Edison had a patent for a coiled wire rheostat in 1872.

Why? The answer is simple, cost. Despite what Cadillac charges for replacements, this device costs only a few cents to make and the computer input circuit, a simple A/D converter, and wiring are also cheap when compared to other non-volatile shaft position detection sensors. Sometimes a simpler technology is more reliable and a good fit for an application. Considering the amount of problems experienced with our roof systems and the feedback systems I would say GM missed the mark with this one. Was it the design engineers or the project managers dictating design constraints? Only a few know the answer to that question.

Don't forget that sometimes dirt or dust was the culprit with the snap crackle pop of volume pots. The "good old days"