Hi, maybe someone can help.

Just bought a 1990 300SL (R129) and find that there is strange erratic behavior in the electronics:
- dials in instrument cluster fluctuating (water temp and oil pressure signal on and off - unmotivated needle movement with MPG and tank dial)
- SRS light sometimes on sometimes off
- wireless door lock sometimes working sometimes not on both doors - sometimes working on passenger door but not on drivers door (new batteries in key remote)
- right rear light sometimes comes on / stays on when turning the ignition off
- door locks (key) not working on doors, but lock (with key) working on trunk
- light in driver side door panel sometimes working sometimes not (checked bulb and door contact, both fine)

Has anybody seen similar behavior and knows how to fix this ? (seems like one of the onboard computers goes wild).

The car has an aftermarket radio installed (Sony) - I was told that aftermarket radios can disturb the onboard electronics.
Can anybody confirm this ?

Thanks much in advance