# Raspberry Pi (192.168.1.24) – fan noise investigation + fix

## TL;DR

Pi fan was spinning unnecessarily high at normal temps. I implemented a simple temperature→PWM curve via a systemd timer.

## Observations (during investigation)

- CPU temp: ~55–60°C
- Fan sensor: `pwmfan` (hwmon1)
- Before: `pwm1=75` → ~2630 RPM at ~56°C
- Test showed lower PWM reduces RPM on this box:
  - `pwm1=60` → ~2125 RPM
  - `pwm1=45` → ~1260 RPM
  - `pwm1=35` → ~770 RPM (still stable at ~56–60°C)

## What I changed (on the Pi)

Created:

- `/usr/local/sbin/pwmfan-curve.sh`
- `/etc/systemd/system/pwmfan-curve.service`
- `/etc/systemd/system/pwmfan-curve.timer`

Enabled:

- `systemctl enable --now pwmfan-curve.timer`

The curve (PWM 0–255) ramps up aggressively above 70°C for safety.

## Safety notes

- The script forces `pwm1_enable=1` (manual mode) and sets `pwm1` based on CPU temp.
- If you later install another fan controller (fancontrol / vendor service), ensure they’re not fighting.

## Related findings

- Docker “extract cleanup DeadlineExceeded / RST_STREAM CANCEL” errors were seen during a large pull; Docker later successfully pulled images.

## Follow-ups

- Consider moving Zabbix off the Pi (saves ~600MB DB data) once target host has disk headroom.