Hi. I'm Smitty. I am a professional appliance repair consultant here to help you diagnose, and repair, your appliance.
Without an actual model number I can not bring up any technical information on the hood.
Safety first! Turn off the breaker that feeds the range and hood. Double check any wires for voltage before you touch them.
Remove the filters and if you can locate the junction box. It will have a door/cover on it that is held in place by a/some screw(s). Check that the wires are well connected. If they are okay then the problem will be in the controls themselves.
If there is a cabinet over the hood look up in there for the wires going to the hood. That will point you to the junction box.
Again without a model number I am sorry, but I can not pull up and parts or specs.
The model number may be behind the filters. Let me know if you need anything else. Regards, Smitty