Why does my blower motor stay on

If your car uses a blower motor controller, it can keep running the blower motor after you shut down the engine. In a vehicle equipped with a blower motor resistor, voltage is reduced by the value of the each resistor based on the position of the fan switch. The lower voltages result in lower fans speeds.

The downside of blower motor resistors is that, in order to reduce voltage, a resistor converts the energy into heat. So car makers switched to pulse width modulation PWM to control the blower fan speeds. The blower motor controller is a solid state device with a power switching transistor that takes its marching orders from the HVAC control head.

They can fail in many different modes. Okay cool. Thanks so much. It's on at a pretty high rate so I think I'll just pull the fuse when I'm not driving it and put it in when the car warms up until the unit "dies" or until I get a moment to try to clean it up and see if I can get a few more 6 years out of it.

You need to replace blower motor resistor module now. I can probably open it up and clean the unit up and see if it works, no harm no foul, still in the same position till the new one arrives. Just busy this week, probably wait till next week, or the week after. Paper delivery vehicle. I drive mi per day, bike the rest. Engine's rebuilt, not running dex, everything's fine now. I'm not claiming I will run it that way for 6 more years.

I'll probably pop my first Maxi and pull the unit out and clean it up and give it a shot until the new one arrives from whatever warehouse. Also, I did ask if I only need the dollar resistor module, or do I need the whole dollar unit. Hey lucky me. It has kicked back on so I'm assuming for now its just some dirty terminals or internals, So I'm just going to open that sucker up this weekend and clean it up with some electronics cleaner. This is one of two things.

First, you have a shorted wire causing the fan to remain on. Second, the HVAC programmer has failed causing the blower motor to remain on. I attached detail on this system but basically the programmer controls this motor and if it is shorted it will keep the blower on all the time. The fact that you are pulling the AC relay out just shows that the programmer is most likely the issue because you are removing power from it.

Follow these troubleshooting steps to do that. This shuts the furnace down and prevents your thermostat from calling for more heat. If the furnace was in the middle of a heating cycle, wait 3 to 4 minutes for the blower fan to stop running. Did your furnace fan stop blowing? If your fan is set to ON, it will run continuously, regardless of whether your furnace is heating or not.

Tip: Avoid setting your fan to ON, it wastes money because it forces the fan motor to run constantly.