QuestionI have a 2004 Infiniti QX56. The front a/c fan is blowing at full speed regardless of fan switch setting or even if in "Auto" mode. Could this be caused by a malfunctioning Fan Control Amplifier or some other control mechanism on the vehicle?
AnswerRobin,
The fan speed is set by your switch. From the switch the voltage travels to a resistor block. At low speed, the voltage travels through 3 or more resistors, knocking voltage down so the fan turns slower. At medium and slow speeds it travels through less and less resistors, until eventually on high, it is getting 12 volts straight to the blower motor. By you telling me that it only blows on high, and nothing else, that tells me that your resistor block is bad. It may be just one (the lowest speed resistor) that is bad, because all of the different speed voltages travels through it, but you will need to replace the entire block.
On most vehicles, this block is located right on the blower motor/evaporator assembly. It should be no more than 2 screws and a plug to unhook it. The hard part is gettig to it though. If you plan on doing the work yourself, I recommend taking the glove box out first and seeing if you can reach it through there. Some you can, some you can't.
I hope I helped you out just a little bit, have a great day and thank you for the question.
