Last night my HVAC blower stopped working. I have a Lennox 80MGF4/5X-100A-12. The A/C condenser and furnace both kick on, but no blower. This morning I opened the access panel and heard the relays click when I turned the FAN switch to ON. Is there a way I can bypass the relay to see if it's the blower or the control board? The control board part number is either 24L8501 or 50A62-121. The fan spins freely.

Many thanks, its going to be in the upper 90's today.

You need to check the motor with an ohm meter. Check the ohms between common and each speed wire like black (high), blue (med.), red (low). Common is probably white and you have two brown wires going to the capacitor. Also, it is very, very important to check the wires continuity to ground. If you get any reading the motor is bad. Most likely the motor is bad, but you need a meter and you need to use it. Here are some instructions: https://dl.dropbox.com/u/8010163/Whirlpool%204322537A%20How%20to%20use%20Test%20Equ ipment%20Service%20Manual.pdf
Write back and give us the readings and I can tell you what to do.