Heater

[Frogurt]

Hello,

I have a 69 C-10, I pushed the lever over to turn the fan on for the heater and nothing. I have left on and as just driving it came on, I did not need at the time so turned it off. Now when I need it I turned on and nothing doesn't work again. Anyone have any ideas what would cause this to happen? It has done this a couple times now. I have checked the fuses, ground. Has new blower motor also new fan about 2 years ago, truck doesn't really get driven that often to use the heater.

Thank you for your help.