Going from what you describe about this problem I think you may have purchased the wrong parts to solve the trouble. My guess is the trouble is coming from the blower relay. The contacts inside it wear over time and can cause the intermittent operation you described. You can verify that by tapping on the relay to see if that makes the blower turn on. You can locate it by turning the blower on and off and listening for the location of the relay click. You will be able to feel the vibration of the relay when you touch it to verify you have the right one.