1999 Sl500
 

Outside air temp display reads -35 degrees F constantly. Anyone have any ideas on troubleshooting this system or where to get temp sensor? Thanks

The same thing happened to my wife's 525i. In addition, those clever guys at BMW decided that if your outside temperature was, in her case -45F, you obvioiusly don't need air conditioning! She knocked her sensor off on a curb on a hot summer day and drove home with no A/C as well.

The temp sensor probe is a bi-metalic resistance type. In other words, if the the sensor is disconnected, your car will show a complete open circuit and the temp will go to as cold as your gauge will read. Thus, the same in the hot direction for a dead short. I would check the connection and then as much of the wiring for a break as I could. You might want to try using a short jumper wire and short the connector at the sensor. Your temp should go to the very hot position if your wire harness is OK. Then it is just a matter of a new sensor probe.

I agree, the system is reading an open circuit so check wiring at the sensor first as this sees the most hostile environment.

Lea