Auto Repair Q&A



Cooling System










Auto Repair Products

how to replace cooling fan switch 1991 chev lumina 3.1 l

go to - register

go to - register - add vehicle and go to repair section for step by step with pics - i think you want the sensor - does the fan turn on when you turn on a/c? have you checked the relay and fuse?

i can send you all the

i can send you all the info,pics and diag. flow charts if you like, will need a email ad to send to.
what kind of problem are you having?, blower motor inop?
let me know, mws919

Basically the fan has a two

Basically the fan has a two or three wire connector gong to it. unplug the connector and unscrew the sensor, install the new one. (a little coolant will spill)

Each coolant fan is

Each coolant fan is controlled by individual cooling fan relays. The primary cooling fan relay coil is grounded through the ECM when vehicle speed is less than the speed set by the ECM and the coolant temperature reaches 227°F with the A/C off, and 223°F with A/C on. The primary cooling fan runs until the ignition switch is turned off, or coolant temperature decreases to 220°F with A/C off, or 216°F with A/C on.
The secondary cooling fan relay coil is grounded through the ECM when the coolant temperature reaches 245°F. The contacts close and voltage is applied to the secondary cooling fan, and on models with the V6 VIN X engine, the generator cooling fan. The fan runs at high speed and will continue with the ignition in RUN position until the coolant temperature lowers to 238°F.

The engine Coolant Temperature Sensor (CTS) provides engine temperature information to the control. The control unit uses this information to determine open-loop/closed loop operation, and make temperature related adjustments to the fuel, ignition and emission control systems.

The Sensor is a thermistor, installed where it protrudes into the engine coolant flow. Its resistance varies with changing temperature. At low temperatures its resistance is high. At high temperatures, its resistance is low. The ECM/PCM sends a 5.0 volt reference signal to sensor through a resistor in the computer, and then monitors the voltage in the circuit. The measured voltage varies with changes in coolant temperature, due to the changing resistance of the sensor. Each measured voltage value corresponds to a specific coolant temperature. By monitoring the circuit voltage, the computer can calculate the engine temperature and make necessary adjustments.

Try for the

Try for the step-by step guide along with pictures for this procedure.
Once at the site identify you car under the heading "current Vehicle"
Next click "Repair Info" on the tabs below the AutoZone logo.
At the middle of the page go to "Your Ride, Your Guide" and click "Become a member" set you username and password
Log-in and click "Vehicle repair guide"
Select the category for the repair needed.
Select (on the left) type of repair needed.
Page opens to your repair info.