I'm having a similar issue with my 2001 Chevy Impala. The odometer gets so dim during daylight you can't read it. The ambient light sensor is not blocked. To compound this issue the gas gauge shows full almost all the time until its on E, sometimes it fluctuates like the RPM meter. I have to keep track of how many miles to know when I need to fill up again, hard to do when you can't read the trip meter. Also the overhead read out that shows direction, MPG, temp seems to reset when the fuel gauge fluctuates. Anyone know what could be causing this?
Our gas gauge used to do as you have descibed. I kept a log to see about how many miles I would get per tank and just reset the trip miles everytime I filled up. We finally had the sensor in the tank replaced. I'm having the problem with the dim odometer during the day now.