Fan only works on high speeds (4-5) - 2004 Chevrolet TrailBlazer

Question edited for clarity.
Question moved to Nissan.

See the link

https://www.google.com/search?q=2015+Nissan+Urvan+NV350+coolant+temperature+sensor

..

check fuse and relay but most likely fan speed resistor or motor failed

Both radiator cooling fans are running all the time ? Key off ? The cooling fan opperation
HOW they work
Cooling Fan Control
The engine cooling fan system consists of 2 cooling fans and 3 relays. The relays are powered by the battery positive voltage circuit and controlled by a switched ground from the powertrain control module (PCM).
During low speed operation, the PCM supplies the ground path for the low speed cooling fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan low relay coil, closes the relay contacts, and supplies battery positive voltage from the COOL FAN LO fuse through the cooling fan motor supply voltage circuit to the cooling fan. During high speed operation the PCM supplies the ground path for the cooling fan low relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan high relay and the s/p cooling fan relay through the high speed fan relay control circuit.
The PCM commands the fan on under the following conditions:
• Engine coolant temperature exceeds approximately 98°C (208°F) Low Fan Speed
• Engine coolant temperature exceeds approximately 102°C (216°F) High Fan Speed
• A/C refrigerant pressure exceeds 361 kPa (52 psi) Low Fan Speed
• A/C refrigerant pressure exceeds 2100 kPa (300 psi) High Fan Speed
• When the engine coolant temperature exceeds 112°C (234°F) at key off, the fan high speed will run for up to 300 seconds. If within that time frame 102°C (216°F) is reached then fan speed will change from high to low speed. If within that time frame 99°C (210°F) is reached then fan speed will change from low to off.
The PCM commands the fan off under the following conditions:
• A/C is requested and engine speed exceeds 6,240 RPM
• Engine coolant temperature exceeds approximately 99°C (210°F) turns the cooling fans from low to off.

sounds like one of the relays are stuck closed .

Cooling Fan Always On
Step
Action
Yes
No
Schematic Reference: Engine Cooling Schematics , HVAC Schematics in HVAC Systems - Manual
Connector End View Reference: Cooling System Connector End Views
DEFINITION: One or both engine cooling fan motors run continuously in high or low speed.
1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, command the Fans Low Speed ON and OFF.
Are one or both cooling fans ON?
Go to Step 3
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
3
Are both cooling fans running continuously?
Go to Step 4
Go to Step 6
4
Are both cooling fans running continuously in high speed?
Go to Step 5
Go to Step 7
5
Test the low reference circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 18
Go to Step 14
6
Important: The S/P relay is located under the front bumper on the drivers side of the vehicle.
Remove the cool fan S/P relay.
Did the right cooling fan turn OFF?
Go to Step 10
Go to Step 8
7
Remove the cool fan LOW relay.
Did the cooling fans turn OFF?

you probably need new control switch.

Hello,
You may want to try your fan on all speeds. If it will work on high, you have a bad resistor for the fan motor. ( high speed doesn't go through the resistor ).
If it doesn't work on any speed, I would check the following;
1. Make sure the fuse isn't blown for the fan blower motor.
2. Check, or have checked the wires between the fan control switch and the fan blower motor.
3. Have the fan control switch checked.
4. Have the fan blower motor checked.

I hope this helps you.

It needs to have the blower motor resistor card replaced.
It still works on high speed because on the high setting the voltage does not go through the resistor.
The resistor is mounted beside the blower motor and is easy to replace.
There you are, thank you for using FixYa.

KL

hi craig cooling fans on those cars have two or three connection wires. two wires means one speed. three wires means two speeds. they work with extra poles in the motor, not with a resistance. when you have a motor with 3 conn. wires and only one speeed, you have to replace the motor. most types haves only one speed. extra speed fan motors where optional for extra heavy duty or high temps. if you have more questions let me know. greetings.

A bad blower motor resistor will cause it. It is located ny the blower motor p.s. below dash.

Hi.....
On your Vehicle the problem for the FAN speed is NOT the FAN switch.
99.9 % of this problem on cars is the BLOWER MOTOR RESISTOR.
The blower motor resistor give the speed to the Fan.
But on High speed the switch make a By pass of the switch using a Relay for the high speed.
The Blower motor resistor, is located Beside of the Blower motor On the passanger compartment.

If you replace the blower motor resistor you have 99.9% of this will solve your problem.

I'm a Mechanic.

I hope this help on your problem.
Thank you for use fixya...

you have what we called resistor block. it is a series of resistor to bring down the voltage of the blower to decrease its speed.

if one resistor is broke, then it would only work on high. they are normally located in the blower housing.
it has four of five wires depending on how many speed you got.

tnx 4 using fixya,

drcool