Weird HVAC Blower Issue - Cycles on and off

[ltemup4650]

All,


I'm having a weird issue with my Driver and Passenger (front) blower/fan for the HVAC.


When I first start the car (with the fan set to its highest setting), it will blow strong on its highest setting. While still on the highest setting, after 30 seconds or so, it slowly goes down to nothing. Meanwhile, the rear seat HVAC keeps blowing away strongly on its highest setting. After a couple minutes, it goes back up to full blast on its own, but only for 30 seconds or so and then decreases back to nothing. It is an endless cycle it seems. When I select defrost, same thing...endless cycle between full blast for seconds, then back to nothing for a couple minutes.



I've read that a weak battery can cause this as the computer reduces the fan speed to save battery (I find this odd because...doesn't the resistor block add in more resistors to lower voltage, thus still drawing amps???). My battery is newer and registered and coded to the car (90ah AGM). The battery is good as I'm reading over 12v with the car off and well into the 13v range while running.



The resistor block (final stage resistor) could be the issue, but I've read that when it fails that it either doesn't work at all, or, it allows the fan to turn on with the ignition off.



I'm wondering who has had this issue and what they might've done to fix it. Thanks in advance.