Cisco 3900-FANASSY
Cisco 3925/3945 Fan Assembly (Bezel included)
Product Highlights
Overheating is one of the most common causes of unplanned router downtime — and in a branch or campus deployment running a Cisco 3900 Series ISR, a failed fan assembly can quickly escalate from a warning log to a full service outage.
The Cisco 3900-FANASSY is the OEM fan assembly and bezel designed for the Cisco 3925, 3925E, 3945, and 3945E Integrated Services Routers. It is an exact replacement for the factory-original cooling unit that ships with every Cisco 3900 ISR Generation 2 chassis, delivering the same port-side intake airflow pattern the router was engineered around.
Because the 3900-FANASSY is hot-swappable, network administrators can replace a degraded or failed fan tray without shutting down the router — keeping branch-office connectivity, voice services, and VPN tunnels online during maintenance. The assembly includes the front bezel (faceplate), so a single part number restores both cooling and chassis aesthetics.
Whether you are proactively stocking spares for a fleet of ISR G2 routers or responding to an ENVMON overtemperature alert, the 3900-FANASSY is the purpose-built solution to keep your Cisco 3900 Series infrastructure running within safe thermal limits.
Features & Benefits
Hot-Swappable Fan Tray
The 3900-FANASSY is designed for hot-swap replacement, meaning you can remove and install the fan assembly while the router is powered on and passing traffic. This eliminates the need for a maintenance window and keeps critical WAN, voice, and VPN services online during the swap.
Optimized Airflow & Thermal Management
Engineered with a port-side intake airflow direction, this fan assembly maintains the precise cooling pattern the Cisco 3900 chassis requires. Proper airflow prevents CPU overtemperature conditions that can trigger critical ENVMON alerts and automatic shutdowns, protecting both uptime and hardware longevity.
Integrated Bezel / Faceplate
The assembly ships with the front bezel (faceplate) included, so you receive a complete unit that restores both cooling function and the clean front-panel appearance of the router. No additional parts are needed.
Broad ISR 3900 Compatibility
Compatible with the Cisco 3925, 3925E, 3945, and 3945E routers, the 3900-FANASSY covers the full range of Cisco ISR G2 3900 Series platforms. Stocking a single spare part number simplifies inventory management across mixed deployments.
Deployment Scenarios
Proactive Spare for Branch Office Deployments
Organizations running Cisco 3925 or 3945 routers at remote branch offices can stock the 3900-FANASSY as a critical spare. Having a replacement fan assembly on hand allows on-site technicians to resolve cooling failures immediately, avoiding extended downtime at locations that may lack rapid parts delivery.
Emergency Replacement After Fan Failure
When a Cisco 3900 Series router logs ENVMON overtemperature warnings or fan RPM anomalies, the 3900-FANASSY provides a drop-in fix. Its hot-swappable design means the router stays online during the replacement, restoring safe operating temperatures without a service interruption.
Lifecycle Maintenance for Aging ISR G2 Fleets
As Cisco 3900 Series routers age, fan bearings and capacitors can degrade. Replacing the fan assembly proactively during scheduled maintenance extends the operational life of the router and prevents cascading thermal damage to CPUs, memory, and service modules.
General
Cooling
Compatibility
Physical
Compatibility Notes
Compatible Router Models
- Cisco 3925 (CISCO3925/K9)
- Cisco 3925E (CISCO3925E/K9)
- Cisco 3945 (CISCO3945/K9)
- Cisco 3945E (CISCO3945E/K9)
Note: This part number (3900-FANASSY) is the standard fan assembly. For NEBS-compliant deployments, see the 3900-FANASSY-NEBS variant, which includes the NEBS fan filter (3900-FANFLTR-NEBS).
Downloads & Resources
Frequently Asked Questions
| Part Number | Product | Key Difference |
|---|---|---|
| 3900-FANASSY-NEBS | Cisco 3925/3945 NEBS Fan Assembly | NEBS-compliant variant that includes the 3900-FANFLTR-NEBS fan filter for telco/central-office environments. |
| PWR-3900-AC | Cisco 3900 Series AC Power Supply | Complementary FRU — if you're replacing the fan assembly, consider inspecting or stocking a spare power supply as well. |
| CISCO3925/K9 | Cisco 3925 ISR G2 Router | The complete router chassis that uses this fan assembly; relevant if a full unit replacement is more cost-effective. |
| CISCO3945/K9 | Cisco 3945 ISR G2 Router | Higher-performance 3900 Series chassis with additional SM slot; also uses the 3900-FANASSY fan assembly. |