I have an ‘87 SDL that the blower will come on in the off position. It will also quit in the on position. If the fan is set to low speed then the blower will come on on it’s on going down the road at low speed. If it’s set on high speed then it can also come on on it’s on at high speed even with the switch clearly in the off position. If I press the off button and hold it then the blower will stay off until I release the switch. Sometimes it will stay off until I press a selection on the climate control unit. Every time it comes on on it’s on the AC compressor comes on too. In other words, mine comes on with the key switch 95% of the time and blows according to the selected fan speed. It will shut off on it’s on. Every time it’s on the AC compressor is on. I hate electronics! ��