Diagnostic Codes (Not the usual questions)
 

Nothing like discovering something you didn't know after owning the catr for a couple of years...

There is a hidden switch in the center of the clock adjuster that when you depress it with a pencil, displays a code in the outside temp display (ignit on). You can cycle through five different codes by turning the clock adjustment clockwise. If you turn it counter-clockwise it cycles through a variety of temperatures in 2.5c degree increments.

Anybody know anything about this and what its good for?

That is interesting - what car?

R129 90-300sl-24

The hidden switch is used to activate tests which verify proper operation of the fuel level, fuel economy, and oil pressure gauges and inputs to the cluster for engine RPMs and fuel level. It is all explained in the diagnostic manual for the instrument cluster.

Also, I seem to remember that the later clusters with the electronic odometer display has a facility for using the hidden switch for calibration of something...It is intuitive that it would be the speedometer/odometer, but I think it did in fact concern fuel consumption.

Thanks. I have the shop manual for this model but it references the body diagnostic manual for details on this. (Which I don't have) Sounds like something I will never use but good to know its there (I think)<grin>

When you turn the clock adjuster to the left it goes through a bunch of temps, is this for adjusting the calibration for the temp sensor on the beak?