Sounds like you may have a problem with the source of the power for your Inst. Cluster .....We always Remove and Replace all of the FUSES About once a year .(under routine Maint.)after removing the fuses take a "small" wire brush and clean the contacts where the fuses seat. for some reason they get a film on them and could drive you up a wall trying to resolve the problem...We were using an after mkt fuse. for years but went back to MB fuses (specal alloy) which resolves the problem . But we still remove Clean and replace fuses . Belts and hoses at different intervels..It is why MB are so reliable and will practally last forever if you keep up on the MAINT>(Somewhat like the Aviation Industry) We Treat our cars like we treat our Airplanes. Hope it helps .Let me know if it resolves your problems.