thermostat broke / best way to regulate temps?

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So my thermostat must be broke, as I have it set for 90, yet my thermometer is recording the temp at 94.

think they'll replace a 4 year old thermostat :I

I would guess not , so I guess I'll have to find another way to regulate the temps until I can get a replacement.
I have a fan that I have used to keep it from getting over 90, but is that bad, do dramatic temp changes like that affect the snakes negatively? (Not that dramatic I guess, only like 4-5 degrees .. but still )