1998 Infinity QX4 Heater/Air Fan won't shut off

[Katarinab]

My 1998 Infinity QX 4's heater fan stays on full blast. I can switch from cold to hot, but cannot turn down the fan speed. Even when I turn off the heat unit from the dash, it still blows at full speed.

[goody90q45]

Welcome to NICO.

Your fan control amplifier is kaput. It's a common problem. It's located behind the glove box downstream of the blower. See page HA-63 of your FSM for replacement instructions (it's simple). The part will be $75-$100.

http://www.nicoclub.com/FSM/QX4/1998_QX4/

[Katarinab]

Seriously? Thank you so much. I sent the info off to my mechanic hoping it will minimize the time it takes to research the issue. I'm trying to "save" my poor old SUV, since it's really in great condition and I don't want a car payment during these economic times.

[goody90q45]

One of the main reasons the amp goes bad is a buildup of dust and dirt on the lightweight fan blades (more of a cylinder) which creates added amp draw on the blower motor and eventually fries a component of the fan amp. With the glove box out the blower motor is easy to remove to clean the blades. Make sure to have the mechanic do this when you replace the amp or you'll be doing it again in a couple of years.