There is a disconnect here... Those boxes are EOL'ed - end of life. I believe you have a hardware issue or as DukeNuke indicated firmware changes are in order. I would look for replacement parts first.
You do understand EOL I'm sure. It is oracle's way of forcing you to pay huge support costs for reduced support, or buy new boxes. Oracle has forced the creation of a kid of cottage industry - old sun boxes and/or refurbished oldies.
One inexpensive workaround to deal with your issue:
Parts are available on off occasions. These boxes, complete, cost less less than most mid range desktops, so that route is your choice.
We had this problem with another different ancient box. We bought several old ones for parts, and those vendors had doc sets as part of the deal. We started with Ebay and then for yet another old Solaris box we switched to vendors like this one:
Buy Sun Fire V215 Server at Solarsystems.com starting at $560
The other choice: live with noisy fans until one fails.
If your box boots and has fmd running (i.e., it has Solaris 10) you can try the
fmadm faulty command as root. Hardware issues are reported there.
So you can at least locate a replacement part to see if that solves your problem.
Solaris 9, which is what those boxes shipped with, does not have fmadm, if I remember correctly. Sun offered Solaris 10 upgrades at no cost.