Battery fan not coming on.

This morning driving into work my 2001 prius went through a "charging event" where it charged the battery up to 94% SOC. It had been at about 38% SOC when I started the hybrid system.

I noticed that my battery temperature rose quickly up to 100F, and kept rising. The fan never came on. It got to 120 before I pulled off the road and opened my trunk and tore off all the carpeting, to see if I could find a loose connector or something on the fan. I couldn't find any loose connections, and I had no tools, so I didn't get much done back there. I guess the next step is to find the wiring diagram, and check for voltage at the fan.

Has anyone seen this happen before? Is there a control relay, or fuse I can check for? Does the system just send a 12V signal to the fan, or is it variable speed (variable voltage)?

Thanks

 

It isn't normal for the battery to reach 120 F without the fan coming on.