Introduction

The side fan is very noisy and runs whenever the unit is on.  An equivalent fan can be substituted  that is virtually silent.

Original Fan

I tracked down the specifications of the original fan.  The details, for reference, are below.  It's possible your fan is a different model, but the specs should be pretty much the same.

• Sanyo SanAce40
• Model number 9A0412J7D07
• 40mm x 40mm axial fan
• 15mm deep
• 12v
• 0.11A
• 6.2 CFM
• 28 dB
• 7500 RPM
• 2 wire

New Fan

The fan I selected is a Sunon Fans model 4129/HA40201V4-1000U-A99.  It is similar to the original with a few important differences.

• 20mm deep
• 5.5 CFM
• 12.3dB

In selecting this fan, I sacrificed a little CFM to get the quietest fan I could.   This fan is nearly perfectly quiet.  If I had to do it over again, I would try to get a little more airflow even at the expense of a little more noise.

Installation

The installation is easy enough, but there are two things you should be aware of.

Bolts

If you select a 20mm deep fan instead of a 15mm (like the original) it will fit, but you do need to replace the original screws with longer ones.  You will need 4 M4x30mm (0.7mm pitch) screws.

Fan Connector

Likely your new fan will come with a connector different than the one on  the existing fan (or it won't be long enough).  I chose to cut the old connector off and use it for the new fan.