Volvo Repair: display lights, wire connections, coolant

Question
I am getting desperate, would really appreciate some ideas! My s80 2.0T, Year 2000, display lights go on and off (emission service, coolant, total break failure). The dealer who sold me this car zeroed these and sent me on my way... in a few days lights went on again (and gradually off by themselves). He said he cleaned the sensors a few days ago, but now I have the same problem. The car seems to work just fine, no heating or anything... Please help!

Answer
Usually when all gauges act up all at once leads me to suspect wiring problem, especially with ground circuit. Need to get a manual and locate the ground wire connections for the dash and check them. Or remove dadh cluster and unplug and re-install connectors, may be loose or poor contact.