Q: hvac blower not working and 30A fuse blown

That 30A fuse powers what is historically known as a blower motor resistor. In the case of your car it is a small computer called the blower motor control processor. It is simply a blower fan speed control. I would remove it and see if it looks melted or appears to have been really hot. I would expect you to find something like this, as this is a very common failure on all vehicles.

It is mounted on the passenger side above their feet, near the blower motor. It has five wires coming out of it. If once you have located this and removed it you don’t see anything physically wrong with it, I would unplug the connector to it and plug in another fuse. If the fuse doesn’t blow, you can be assured the wire coming from the fuse box is good. If the fuse blows with the blower resistor disconnected, then you have a wire shorted to ground somewhere from the fuse box to the resistor. Now you will need to locate it. I recommend running a new wire altogether if this is the case. Finding a shorted wire in the harness that runs through your dash will take many hours.

If the fuse doesn’t blow, the likely culprit is the blower motor controller. If there isn’t a sign of melting or being hot, I would power the blower motor with a jumper wire to see what it does. Ideally, you need an inductive amp clamp to monitor how much current the blower motor is pulling. If it exceeds 30 amps for a sustained period of time, I would replace it. Keep in mind, when an electric motor first starts working, the current will spike. Most likely above 30 amps. This is normal. What you want to monitor is the sustained current when the motor is operating. Most electrical systems such as this should run a current %50 to %70 of the maximum. Which in this case is 30 amps.

If there is a problem with the motor, you will likely have other indicators like, the motor won’t run, or it will get really hot to the touch. If you have determined there is a problem with the blower motor, I would advise you to replace the blower motor controller as well. They don’t take kindly to higher than designed electrical currents and it is likely damaged. Lastly, if the blower motor controller has been hot or melted, test the blower motor to make sure it isn’t pulling excessive current.

If you feel like you need some assistance with this, feel free to contact a certified mechanic who can diagnose your electrical issue with your blower motor resistor. Once that is done, they can assist you with replace your blower motor resistor as necessary and ensure that it’s properly functioning.

Good luck.