[j-nsp] MX480 AC Power Supply fan replacement problem?

[Chris Cappuccio]

So, I had four MX 480 AC power supplies, across two totally different and
unrelated routers, all four of them have fan failures reported by JunOS.
These fans failed within a span of 6 months.

The old fans are definitely bad. On any given power supply, one of the
two fans are seized. Maybe both. So, the diagnosis given by JunOS appears
to be correct. I ordered Delta Electronics FFB0412SHN, the exact fan that
failed. I guess.

The new fan wires are neatly soldered in place. The connections are tight.
When the power supplies are re-installed, the new fans spin continuously. So,
you would think, we are ok? But, JunOS still detects fan failure, and the
alarm light on the front of the router goes on. 

Is there something that can be reset in the power supply? Or perhaps the
sensor wire is sending a different signal? Any ideas?

Chris