Hot end peaks at 145 then drops back down

I'm on the Hot-End test stage of my Fisher setup and when I set the hot end to heat up to 190 it went up from room temp to around 145 very quickly. However, when it hit around that area, the temperature just began to drop again.
I had initially thought that maybe something got too hot and un-soldered itself but had a quick glance at the hot-end and can't see any sort of damage or anything out of place.
Does anyone have any suggestions?

The heater is probably timing out. If you switch to the Gcode Console table of the web interface, there may be an error message. See [reprap.org].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].