I posted this as an addition to a question I earlier asked, but since I didn't receive any answers, I'm trying it as it's own separate question... To start from scratch: my heat isn't coming on, and so I checked the fuse panel and the light was blinking eight times, indicating "Internal code fault". Somewhat strangely, it's also now impossible to turn off the fan for either the ac or the heat; it's like I have the setting set to "ON" instead of "Auto". That started when we had a power outage recently, and I've tripped the breakers to no avail (obviously it shuts off when I turn the power off, but as soon as I turn it back on, the fan kicks in.)
So: 1.) are these two issues related
2.) How does one go about fixing an "Internal code fault?" Are there wires I should check, fuses I should try and replace? Etc...
Thanks in advance.

Open high or auxiliary limits are the normal culprit for this behavior. You will need a multimeter to check continuity and of course be able to operate said meter. ;-)