DeVere 504 timer question

The timer on my Devere 504 has stopped timing however I have an old F-stop style timer that I have put before the Devere timer and the transformer, effectively controlling the duration of power to the transformer.
Everything works now through the f-stop style timer with one exception: previously the fan ran constantly regardless of wether the enlarger lamp was on or not. With the "new" arrangement the fan only now comes on and turns off with the enlarger lamp. If the image is focussed or exposed for a long time the fan is on for that duration. The head of the enlarger seems to my touch to be no hotter than before so my question relates to any problems I may be missing.

I much prefer the new arrangement because the Devere timer was [for me] a PITA. I have printed for years using RH design f stop timers and much prefer that system.