Hello! This is the place where questions are answered, so here goes… 
I have a 1998 Sienna (at 300k miles I want to drive until it’s dead) and the dashboard has lost illumination in several bulbs. The fuses are good and the bulbs seem fine, but there is a bad connection somewhere. I would like to start cleaning contacts in some of the junctions before tearing the dash apart again.
Which brings me to the big question: where should I look for connections that I can clean so I am sure the electrical system is providing a proper current to the dash bulbs? Besides the idiot lights (working), all I have at the moment is a single bulb that illuminates half the speedometer, while the tach and rest of the dash and air conditioning controls are dark. As I’ve had other wiring harness connections become corroded and need cleaning over time, I could use some help determining where to begin opening connections to clean before tearing the dash apart.
Many thanks!!!
On that vehicle, you’ll likely need to remove the printed circuit board cluster to get at the bulbs. It’s a laborious process.
Here’s a site with pictures for a similar Toyota setup. http://www.mr2spyder.net/spyderweb/index.php?/topic/1850-mr2-spyder-gauge-cluster-disassembly-how-to/
how do you know the bulbs are fine? As Joe says, it is difficult to access them.
Led lighting with shielding against your eyes could be a workaround.
Thanks everybody! The only reason I believe the bulbs are fine is because when the first couple of them went out I opened the dash and tried replacing them; no joy. Since then I have had a couple more electrical ghosts that turned out to be simple connection issues, so I’d rather try cleaning before I open the dash again. I’ll definitely consider the LED lights idea, that could be a great alternative as well!
As far as the other lights, have you checked the fuses? The fuses marked Panel and Tail. The reostat feeds the lights. Do the lights dim when the Reostat is turned?
Here is the meter illumination. I’m sure that you could replace the bulbs yourself. They may be solder in, not sure.