SWR Bass amp fan issue

[rosssurf]

I have an SWR bass 350 2 space bass amplifier. It has a fan switch on the outside to shut the fan off to reduce noise in case of close proximity to recording microphones. Even with this switch not set to "Defeat' but set to "Fan" it still does not come on at all. I checked the switch with a MM and it seems to be fine. Does anyone know if the fan in this only comes on if it needs to? Is there a way I can test or repair this fan? Maybe it is somthing in the amp circuit that switches the fan on that is not working. Other than this issue the amp sound fine and works as it should.
Thanks in adavance for your help/

[Enzo]

Hit the temp sensor with a heat gun and see if the fan comes on.