Have you used those functions in a while?

Sometimes those buttons can get a bit sticky. Try tapping them (engaging & disengaging) a few times fast to loosen them up before trying to do the tests listed above.

Also ...... double check to make sure they are the correct buttons (I realize that might sound a bit stupid, but sometimes people are actually pressing the wrong combination of buttons).

Pay close attention to the details listed above for your model pushbutton control unit and try again.

A/C unit is working ok ???

 

This is for SL600_Cruzin. Your detailed answer about the 95 temp guage in July 2005 was very informative. I have an early 95 C280(manufactured in november 94) which required a replacement evaperator last August. I have now experienced some erratic distribution and motor problems which today culminated in full hot and no indications (led lites and temp indicator) on the controller, as well as being unable to control either temperature or motor speed. I have tried some of your troubleshooting techniques to no avail because it seems there's no power on the controller. However, if you switch the ignition to the very first position (where you can see the airbag light with a door open) if you push the REST button, the light flashes and you can hear clicks behind the instrument panel. I'm prepared to have to replace the controller now, but I'm curious as to whether this failure might have been induced by the replacement of the evaporator, since the instrument panel had to be removed to do that. Any ideas would be gratefully appreciated. Thanks

 

Found the trouble. Both connectors to the puchbutton controller were not fully mated. Problen solved.
Thanks,
Jack L.