Mathew Valiakulathil
New member
Hey all. I finished my build earlier this summer and ran into this fan issue. I've just gotten some time to sit down and troubleshoot it.
I verified that there was no shorts at the CAT5 jack between the pins. Using a post that someone else had with the same issue I also verified 12 VDC between blower and ground when the fan was at 0/100.
I switched the mode to Pulse for the Fan output and measured voltages for ATMega Pin 5, Q1 and Q3. This was taken without the blower connected.
Pulse Mode - Fan 100%
AT Mega 3.3 VDC
Q1 Right 0.0135 VDC
Q1 Center 3.3 VDC
Q1 Left 0.0003 VDC
Q3 Right 11.9 VDC
Q3 Center 11.9 VDC
Q3 Left 0.0136 VDC
Pulse Mode - Fan 0%
AT Mega 0.0039 VDC
Q1 Right 4.6 VDC
Q1 Center 0.0039 VDC
Q1 Left 0.0002 VDC
Q3 Right 11.9 VDC
Q3 Center 11.9 VDC
Q3 Left 0.0136 VDC
I also switched the Fan Output back to Voltage Mode and saw the same behavior. It seems to me that the issue is with Q3 since the Control leg is not getting 12 VDC when the Fan Output changes. Do you guys have any other thoughts on what it could be?
I verified that there was no shorts at the CAT5 jack between the pins. Using a post that someone else had with the same issue I also verified 12 VDC between blower and ground when the fan was at 0/100.
I switched the mode to Pulse for the Fan output and measured voltages for ATMega Pin 5, Q1 and Q3. This was taken without the blower connected.
Pulse Mode - Fan 100%
AT Mega 3.3 VDC
Q1 Right 0.0135 VDC
Q1 Center 3.3 VDC
Q1 Left 0.0003 VDC
Q3 Right 11.9 VDC
Q3 Center 11.9 VDC
Q3 Left 0.0136 VDC
Pulse Mode - Fan 0%
AT Mega 0.0039 VDC
Q1 Right 4.6 VDC
Q1 Center 0.0039 VDC
Q1 Left 0.0002 VDC
Q3 Right 11.9 VDC
Q3 Center 11.9 VDC
Q3 Left 0.0136 VDC
I also switched the Fan Output back to Voltage Mode and saw the same behavior. It seems to me that the issue is with Q3 since the Control leg is not getting 12 VDC when the Fan Output changes. Do you guys have any other thoughts on what it could be?