Finished installing a heater core in our 01 S-10 Blazer 4X4 the other day and there is a noise that kinda sounds like an electric razor or something coming from the heater box.. The noise is only heard when the key is in the off position turn the key to the on position and the noise stops.. This crazy noise continues until the battery is dead.. Anyone ever heard of anything like this before??
Thanx in advance and God bless!!!

 

If I'm not mistaken behind/ under glovebox is blower motor and resistor and actuators of a/candheat. One of those are going bad . I had replace my heater core in my 02 trailblazer and I remember seeing those part under dash . I hope this helps