The Air 903 is a budget case that cools like an expensive one. It comes with big 140 mm fans behind a wide-open mesh front, and room for nine fans in total.
The stock layout is already good. Here’s what to add, which way it should blow, and one fan speed setting to steer clear of.
The layout to copy
| Fan spot | Fits | Set it to |
|---|---|---|
| Front | 3 x 120 or 3 x 140 mm | Intake |
| Rear | 1 x 120 or 140 mm | Exhaust |
| Top | 3 x 120 or 2 x 140 mm | Exhaust |
| PSU shroud | 2 x 120 mm | Intake, optional |
All spots are from Montech’s spec sheet. Cool air comes in the front and the shroud, and warm air leaves through the top and back.
What’s in the box: MAX or BASE
Both versions use Montech’s HP140 fans, but how many you get differs.
| Version | Front | Rear | Fan hub |
|---|---|---|---|
| Air 903 MAX | 3 x 140 mm ARGB | 1 x 140 mm | Yes, up to 6 devices |
| Air 903 BASE | 2 x 140 mm | 1 x 140 mm | No |
KitGuru confirms the stock fans run front intake and rear exhaust. The MAX’s hub handles fans and lighting, and KitGuru notes it supports up to six devices in total.
Which fans to add first
No reviewer has tested added fans in the Air 903, so this order is our suggestion, based on how the case moves air.
On the BASE:
- A third front fan. The front has room for three 140 mm fans and only two come installed. Matching the MAX’s front is the easiest upgrade.
- Top exhaust. Gives warm air from the CPU cooler a short way out.
On the MAX:
- Top exhaust. Add it if your CPU runs hot, especially with a big air cooler.
- Shroud intake. Two 120 mm fans under the graphics card. See our bottom intake fans guide for when these help.
KitGuru found that taking panels off had barely any effect on cooling. The mesh front already lets plenty of air in, so extra fans help more than opening up the case.
Skip the 40 to 49% fan speed band
Tom’s Hardware found that when the case fans run in PWM mode between 40% and 49% speed, the noise oscillates, constantly going up and down.
Set your fan curve to jump over that band, for example from 35% straight to 50%.
If you plug extra fans into a motherboard splitter, check the load with our fan header calculator first.
Air 903 size limits
From Montech’s spec sheet:
| Part | Limit |
|---|---|
| Graphics card | 400 mm long |
| CPU cooler | 180 mm tall |
| Power supply | ATX, up to 240 mm |
| Radiators | Front or top, up to 360 mm |
With room for a 360 mm radiator up front or on top, you can choose. For help deciding, see our sister site’s front vs top radiator guide.
Related guides
- Lian Li Lancool 217 setup, another mid-tower with big front fans.
- Fan direction checker, if you’re not sure which way a new fan blows.