The phototransistor that determines night/day mode is somewhere built into the instrument cluster.
There can be 3 different types of instrument clusters...but the phototransistor is probably located in the same place for all 3:
- Basic
- 6WA (high version)
- 6WB (all digital version)
You can see 2 of the different clusters below...the 6WA (which has a digital display that goes all the way across the bottom section of the cluster and the anodized rings are open on the bottom (similar to a horseshoe) when the cluster is off. The basic cluster has 4 anodized rings that are full circle, and you can still see the gauge graphics when the car is turned off.