The Young Lin DFB401024H fan that comes in the Back-UPS XS 900 VA (BX900R) uninterruptible power supply is rated for 50,000 hours or 5.7 years. At some point the bearings will fail and it will start screeching. Here’s how I replaced the fan.
The first challenge is finding an equivalent 24-volt brushless fan. Last time I replaced one of these, I used an Orion OD4010-24HB fan, sourced from Digi-Key. They are out of stock on that one. This time, I used an Orion OD4010-24MB, which has Air Flow of 6.0 CFM vs. the 7.0 CFM of the OD4010-24HB, but still has ball bearings (longer life than sealed sleeve OD4010-24HSS). The original Young Lin DFB401024H had air flow of 6.4 CFM, so pretty close.
This YouTube video has some helpful information but I wanted to document the actual disassembly and replacement steps. Use these instructions at your own risk!
- Remove the UPS battery.
- Remove back of UPS (four screws).
- Remove two screws inside battery compartment. Note that one goes through black wire connector.
- Pry off front cover with a screwdriver. Remove three screws under front cover.
- Place unit on left side (as viewed from front). Lift off right side. There is a loose black plastic thing covering the yellow transformer. If it falls off, just set it back on the transformer.
- Temporarily attach battery and check air flow direction. (I forgot this this time!)
- Lift out circuit board. Unplug fan from circuit board. Unscrew fan from front of fan.
- Attach new fan. I used crimp-on phone splice connectors to connect new fan to old two-print plug.
- Screws were too short because new fan did not have recessed screw holes. Use a 13/64 drill bit to create recess in new fan screw holes.
- Screw in fan. Plug into circuit board. Temporarily attach battery to test fan. Air flow is front-to-back; I think that’s right, since it means it goes directly to a heat sink, if that’s that is behind the fan mount, and eventually out the top of the unit.
- Reassemble everything. Be careful to get the front ribbon cable into its slot.